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Innovative Materials and Methods for the Removal of Pollutants from the Environment

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 70165

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Guest Editor
Department of Science and Technological Innovation, University of Eastern Piedmont, 1920133 Milano, Italy
Interests: development of innovative materials for the catalytic abatement of toxic molecules; novel catalysts for green processes; optimization of porous sorbents for CO2 capture and/or water decontamination; novel materials for the production of energy through processes with low environmental impact; preparation of inorganic and hybrid organic-inorganic additives for polymer nanocomposites
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Department of Pharmaceutical Sciences, University of Perugia, Via del Liceo 1, 06123 Perugia, Italy
Interests: zirconium phosphate based materials; treatment of wastewater
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the last decade, environmental pollution has reached worrying proportions, and intensive efforts have been devoted to seeking solutions that can be effectively employed for the removal of pollutants from different environmental compartments.

This Special Issue aims to gather the most recent and significant contributions related to innovative materials and processes for environmental purposes, with special emphasis on the depollution of air, water, and soil.

Novel applications of inorganic, organic, or hybrid materials with porous or layered structures for the removal of pollutants through adsorption processes and/or (catalytic) transformation of noxious compounds into species with reduced environmental impact will be of special interest. This Special Issue will include, but is not limited to, new synthetic and characterisation methods for the production of cheap and environmentally friendly materials, as well as characterisation methods for and investigations on pollutant removal processes (with applications to synthetic and real effluents), by experimental and theoretical techniques.

Contributions concerning the removal and/or transformation of emerging contaminants (i.e., synthetic or naturally occurring chemicals not commonly monitored in the environment but with potential or suspected adverse ecological and/or human health effects), such as pesticides or pharmaceuticals, industrial chemicals, surfactants, and personal care products, are strongly encouraged

Prof. Chiara Bisio
Dr. Monica Pica
Guest Editors

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Keywords

  • Environmental depollution
  • Adsorption processes
  • Catalytic decontamination
  • Porous and layered materials
  • Characterization methods

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Published Papers (18 papers)

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Research

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19 pages, 20447 KiB  
Article
Highly Efficient Methylene Blue Dye Removal by Nickel Molybdate Nanosorbent
by Souad Rakass, Hicham Oudghiri Hassani, Ahmed Mohmoud, Fethi Kooli, Mostafa Abboudi, Eman Assirey and Fahd Al Wadaani
Molecules 2021, 26(5), 1378; https://doi.org/10.3390/molecules26051378 - 04 Mar 2021
Cited by 10 | Viewed by 2379
Abstract
Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO4) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the [...] Read more.
Removing methylene blue (MB) dye from aqueous solutions was examined by the use of nickel molybdate (α-NiMoO4) as an adsorbent produced by an uncomplicated, rapid, and cost-effective method. Different results were produced by varying different parameters such as the pH, the adsorbent dose, the temperature, the contact time, and the initial dye concentration. Adsorbent dose and pH had a major removal effect on MB. Interestingly, a lower amount of adsorbent dose caused greater MB removal. The amount of removal gained was efficient and reached a 99% level with an initial methylene blue solution concentration of ≤160 ppm at pH 11. The kinetic studies indicated that the pseudo-second-order kinetic model relates very well with that of the obtained experimental results. The thermodynamic studies showed that removing the MB dye was favorable, spontaneous, and endothermic. Impressively, the highest quantity of removal amount of MB dye was 16,863 mg/g, as shown by the Langmuir model. The thermal regeneration tests revealed that the efficiency of removing MB (11,608 mg/g) was retained following three continuous rounds of recycled adsorbents. Adsorption of MB onto α-NiMoO4 nanoparticles and its regeneration were confirmed by Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) analysis. The results indicated that α-NiMoO4 nanosorbent is an outstanding and strong candidate that can be used for removing the maximum capacity of MB dye in wastewater. Full article
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13 pages, 1755 KiB  
Article
Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases
by Vanessa Miglio, Chiara Zaccone, Chiara Vittoni, Ilaria Braschi, Enrico Buscaroli, Giovanni Golemme, Leonardo Marchese and Chiara Bisio
Molecules 2021, 26(5), 1316; https://doi.org/10.3390/molecules26051316 - 01 Mar 2021
Cited by 7 | Viewed by 2139
Abstract
This study focused on the application of mesoporous silica monoliths for the removal of organic pollutants. The physico-chemical textural and surface properties of the monoliths were investigated. The homogeneity of the textural properties along the entire length of the monoliths was assessed, as [...] Read more.
This study focused on the application of mesoporous silica monoliths for the removal of organic pollutants. The physico-chemical textural and surface properties of the monoliths were investigated. The homogeneity of the textural properties along the entire length of the monoliths was assessed, as well as the reproducibility of the synthesis method. The adsorption properties of the monoliths for gaseous toluene, as a model of Volatile Organic Compounds (VOCs), were evaluated and compared to those of a reference meso-structured silica powder (MCM-41) of commercial origin. Silica monoliths adsorbed comparable amounts of toluene with respect to MCM-41, with better performances at low pressure. Finally, considering their potential application in water phase, the adsorption properties of monoliths toward Rhodamine B, selected as a model molecule of water soluble pollutants, were studied together with their stability in water. After 24 h of contact, the silica monoliths were able to adsorb up to the 70% of 1.5 × 10−2 mM Rhodamine B in water solution. Full article
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22 pages, 5254 KiB  
Article
Volcanic Rock Materials for Defluoridation of Water in Fixed-Bed Column Systems
by Wondwosen Sime Geleta, Esayas Alemayehu and Bernd Lennartz
Molecules 2021, 26(4), 977; https://doi.org/10.3390/molecules26040977 - 12 Feb 2021
Cited by 9 | Viewed by 2795
Abstract
Consumption of drinking water with a high concentration of fluoride (>1.5 mg/L) causes detrimental health problems and is a challenging issue in various regions around the globe. In this study, a continuous fixed-bed column adsorption system was employed for defluoridation of water using [...] Read more.
Consumption of drinking water with a high concentration of fluoride (>1.5 mg/L) causes detrimental health problems and is a challenging issue in various regions around the globe. In this study, a continuous fixed-bed column adsorption system was employed for defluoridation of water using volcanic rocks, virgin pumice (VPum) and virgin scoria (VSco), as adsorbents. The XRD, SEM, FTIR, BET, XRF, ICP-OES, and pH Point of Zero Charges (pHPZC) analysis were performed for both adsorbents to elucidate the adsorption mechanisms and the suitability for fluoride removal. The effects of particle size of adsorbents, solution pH, and flow rate on the adsorption performance of the column were assessed at room temperature, constant initial concentration, and bed depth. The maximum removal capacity of 110 mg/kg for VPum and 22 mg/kg for VSco were achieved at particle sizes of 0.075–0.425 mm and <0.075 mm, respectively, at a low solution pH (2.00) and flow rate (1.25 mL/min). The fluoride breakthrough occurred late and the treated water volume was higher at a low pH and flow rate for both adsorbents. The Thomas and Adams–Bohart models were utilized and fitted well with the experimental kinetic data and the entire breakthrough curves for both adsorbents. Overall, the results revealed that the developed column is effective in handling water containing excess fluoride. Additional testing of the adsorbents including regeneration options is, however, required to confirm that the defluoridation of groundwater employing volcanic rocks is a safe and sustainable method. Full article
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22 pages, 1495 KiB  
Article
Application of Natural Clinoptilolite for Ammonium Removal from Sludge Water
by Stephan Wasielewski, Eduard Rott, Ralf Minke and Heidrun Steinmetz
Molecules 2021, 26(1), 114; https://doi.org/10.3390/molecules26010114 - 29 Dec 2020
Cited by 8 | Viewed by 2149
Abstract
Sludge water (SW) arising from the dewatering of anaerobic digested sludge causes high back loads of ammonium, leading to high stress (inhibition of the activity of microorganisms by an oversupply of nitrogen compounds (substrate inhibition)) for wastewater treatment plants (WWTP). On the other [...] Read more.
Sludge water (SW) arising from the dewatering of anaerobic digested sludge causes high back loads of ammonium, leading to high stress (inhibition of the activity of microorganisms by an oversupply of nitrogen compounds (substrate inhibition)) for wastewater treatment plants (WWTP). On the other hand, ammonium is a valuable resource to substitute ammonia from the energy intensive Haber-Bosch process for fertilizer production. Within this work, it was investigated to what extent and under which conditions Carpathian clinoptilolite powder (CCP 20) can be used to remove ammonium from SW and to recover it. Two different SW, originating from municipal WWTPs were investigated (SW1: c0 = 967 mg/L NH4-N, municipal wastewater; SW2: c0 = 718–927 mg/L NH4-N, large industrial wastewater share). The highest loading was achieved at 307 K with 16.1 mg/g (SW1) and 15.3 mg/g (SW2) at 295 K. Kinetic studies with different specific dosages (0.05 gCLI/mgNH4-N), temperatures (283–307 K) and pre-loaded CCP 20 (0–11.4 mg/g) were conducted. At a higher temperature a higher load was achieved. Already after 30 min contact time, regardless of the sludge water, a high load up to 7.15 mg/g at 307 K was reached, achieving equilibrium after 120 min. Pre-loaded sorbent could be further loaded with ammonium when it was recontacted with the SW. Full article
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16 pages, 3065 KiB  
Article
Evidence for Phytoremediation and Phytoexcretion of NTO from Industrial Wastewater by Vetiver Grass
by Abhishek RoyChowdhury, Pallabi Mukherjee, Saumik Panja, Rupali Datta, Christos Christodoulatos and Dibyendu Sarkar
Molecules 2021, 26(1), 74; https://doi.org/10.3390/molecules26010074 - 26 Dec 2020
Cited by 8 | Viewed by 2628
Abstract
The use of insensitive munitions such as 3-nitro-1,2,4-triazol-5-one (NTO) is rapidly increasing and is expected to replace conventional munitions in the near future. Various NTO treatment technologies are being developed for the treatment of wastewater from industrial munition facilities. This is the first [...] Read more.
The use of insensitive munitions such as 3-nitro-1,2,4-triazol-5-one (NTO) is rapidly increasing and is expected to replace conventional munitions in the near future. Various NTO treatment technologies are being developed for the treatment of wastewater from industrial munition facilities. This is the first study to explore the potential phytoremediation of industrial NTO-wastewater using vetiver grass (Chrysopogon zizanioides L.). Here, we present evidence that vetiver can effectively remove NTO from wastewater, and also translocated NTO from root to shoot. NTO was phytotoxic and resulted in a loss of plant biomass and chlorophyll. The metabolomic analysis showed significant differences between treated and control samples, with the upregulation of specific pathways such as glycerophosphate metabolism and amino acid metabolism, providing a glimpse into the stress alleviation strategy of vetiver. One of the mechanisms of NTO stress reduction was the excretion of solid crystals. Scanning electron microscopy (SEM), electrospray ionization mass spectrometry (ESI-MS), and Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the presence of NTO crystals in the plant exudates. Further characterization of the exudates is in progress to ascertain the purity of these crystals, and if vetiver could be used for phytomining NTO from industrial wastewater. Full article
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20 pages, 15143 KiB  
Article
An Analysis of Exhaust Emission of the Internal Combustion Engine Treated by the Non-Thermal Plasma
by Ming-Hsien Hsueh, Chia-Nan Wang, Meng-Chang Hsieh, Chao-Jung Lai, Shi-Hao Wang, Chia-Hsin Hsieh, Tsung-Liang Wu and Jo-Hung Yu
Molecules 2020, 25(24), 6041; https://doi.org/10.3390/molecules25246041 - 21 Dec 2020
Cited by 6 | Viewed by 2558
Abstract
Industries’ air pollution causes serious challenges to modern society, among them exhaust gases from internal combustion engines, which are currently one of the main sources. This study proposes a non-thermal plasma (NTP) system for placement in the exhaust system of internal combustion engines [...] Read more.
Industries’ air pollution causes serious challenges to modern society, among them exhaust gases from internal combustion engines, which are currently one of the main sources. This study proposes a non-thermal plasma (NTP) system for placement in the exhaust system of internal combustion engines to reduce the toxic contaminants (HC, CO, and NOx) of exhaust gases. This NTP system generates a high-voltage discharge that not only responds to the ion chemical reaction to eliminate NOx and CO, but that also generates a combustion reaction at the local high temperature of plasma to reduce HC. The NTP system was designed on both the front and rear of the exhaust pipe to analyze the difference of different exhaust flow rates under the specified frequency. The results indicate that the NTP system can greatly reduce toxic contaminants. The NTP reactor placed in the front of exhaust pipe gave HC and CO removal efficiency of about 34.5% and 16.0%, respectively, while the NTP reactor placed in the rear of exhaust pipe gave NOx removal efficiency of about 41.3%. In addition, the voltage and material directly affect the exhaust gases obviously. In conclusion, the proposed NTP system installed in the exhaust system can significantly reduce air pollutants. These results suggest that applying NTP to the combustion engine should be a useful tool to simultaneously reduce both emissions of NOx and CO. Full article
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16 pages, 2431 KiB  
Article
Investigating the Aging Effects of Biochar on Soil C and Si Dissolution and the Interactive Impact on Copper Immobilization
by Shaojun Jiang, Jiachen Wu, Lianxin Duan, Sheng Cheng, Jian Huang and Tao Chen
Molecules 2020, 25(18), 4319; https://doi.org/10.3390/molecules25184319 - 21 Sep 2020
Cited by 7 | Viewed by 1944
Abstract
Aging tests were used to investigate the long-term effects of BC on the immobilization of Cu, and the soil silicon dissolution of three types soils (black soil, (BS), vegetable garden soil (VS) and red soil (RS)). Litchi branch biochars (BC) at 10% ( [...] Read more.
Aging tests were used to investigate the long-term effects of BC on the immobilization of Cu, and the soil silicon dissolution of three types soils (black soil, (BS), vegetable garden soil (VS) and red soil (RS)). Litchi branch biochars (BC) at 10% (w/w) were incubated with three Cu (400 mg/kg) contaminated soils. The effect on soil properties of pH, soil organic carbon (SOC), dissolved organic carbon (DOC) and available silicon content were investigated, along with the speciation distribution of Cu. The results indicated that SOC, DOC, and available silicon content (except, BC300) increased with the application of BCs. On the other hand, the DTPA (diethylenetriaminepentaacetic acid) extractable Cu content in BS, VS and RS soils were reduced by 4–12%, 18–25%, and 12–19%, respectively. The Cu availability in all soils first increased, and then decreased during the aging process. The sum of the other four fractions, including the carbonate fraction and the inert component increased by 4–4.5% (BS), 1.4–2.1% (VS), and 0.5–1% (RS) respectively, over the long-term process. Moreover, during the whole aging process, the soil properties (such as pH, SOC, DOC and available silicon content) were almost stable. This study demonstrates that BCs, especially those produced at a higher temperature, are superior to those been produced at 300 °C in immobilizing Cu and releasing available silicon in soils. However, the remediation efficiencies were restricted by the soil type contamination status and remediation time. Full article
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15 pages, 1606 KiB  
Article
Competitive Interaction of Phosphate with Selected Toxic Metals Ions in the Adsorption from Effluent of Sewage Sludge by Iron/Alginate Beads
by Hanna Siwek and Krzysztof Pawelec
Molecules 2020, 25(17), 3962; https://doi.org/10.3390/molecules25173962 - 31 Aug 2020
Cited by 2 | Viewed by 1983
Abstract
Wastewater is characterized by a high content of phosphate and toxic metals. Many studies have confirmed the sorption affinity of alginate adsorbents for these ions. In this study, the adsorption of phosphate from effluent of sewage sludge on biodegradable alginate matrices cross-linked with [...] Read more.
Wastewater is characterized by a high content of phosphate and toxic metals. Many studies have confirmed the sorption affinity of alginate adsorbents for these ions. In this study, the adsorption of phosphate from effluent of sewage sludge on biodegradable alginate matrices cross-linked with Fe3+ ions (Fe_Alg) was investigated. Kinetics and adsorption isotherms were tested in laboratory conditions in deionized water (DW_P) and in the effluent (SW_P), and in the same solutions enriched in toxic metals ions—Cu2+, Cd2+, Pb2+, and Zn2+ (DW_PM and SW_PM). Batch experiments were performed by changing the concentration of phosphate at constant metal concentration. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data for both metals and phosphate. The Freundlich equation provided the best fit with the experimental results of phosphate adsorption from DW_P and DW_PM, while the adsorption from SD_P and SD_PM was better described by the Langmuir equation. For tested systems, the affinity of the Fe_Alg for metal ions was in the following decreasing order: Pb2+ > Cu2+ > Cd2+ > Zn2+ in DW_PM, and Pb2+ > Cu2+ > Cd2+ > Zn2+ in SW_PM. The metals’ enrichment of the DW_P solution increased the affinity of Fe_Alg beads relating to phosphate, while the addition of the metals of the SW_P solution decreased this affinity. Full article
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19 pages, 3293 KiB  
Article
Application of Pineapple Leaves as Adsorbents for Removal of Rose Bengal from Wastewater: Process Optimization Operating Face-Centered Central Composite Design (FCCCD)
by Siham S. Hassan, Ahmed S. El-Shafie, Nourhan Zaher and Marwa El-Azazy
Molecules 2020, 25(16), 3752; https://doi.org/10.3390/molecules25163752 - 18 Aug 2020
Cited by 32 | Viewed by 4183
Abstract
Adsorptive removal of rose bengal (RB) from contaminated water samples was approached using pineapple leaves (PAL). Three adsorbents were utilized for that purpose; raw pineapple leaves (RPAL) and the thermally activated bio-waste leaves at 250 and 500 °C. Two measures were executed to [...] Read more.
Adsorptive removal of rose bengal (RB) from contaminated water samples was approached using pineapple leaves (PAL). Three adsorbents were utilized for that purpose; raw pineapple leaves (RPAL) and the thermally activated bio-waste leaves at 250 and 500 °C. Two measures were executed to evaluate the functionality of exploited biomasses; percentage removal (%R) and adsorption capacity (qe). Face-centered central composite design (FCCCD) was conducted to experiment the influence of variables on the %R. Dose of PAL as adsorbent (AD), concentration of RB (DC), pH and contact time (CT), were the inspected factors. Existence of functional groups and formation of activated carbon was instigated employing Fourier-transform infrared (FT-IR) and Raman spectroscopies. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses were used to explore surface features. Thermal behavior of adsorbents was studied using thermogravimetric analysis (TGA). The surface area and other surface structural properties were established using the Brunauer Emmett-Teller (BET) analysis. An amount of 92.53% of RB could be removed with an adsorption capacity of 58.8 mg/g using a combination of pH 5.00 ± 0.20, RPAL dose of 0.05 mg/50 mL, and 10-ppm RB for 180 min. Equilibrium studies divulge a favorable adsorption that follows the Freundlich isotherm. Pseudo-second-order model explains the observed adsorption kinetics. Full article
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16 pages, 3955 KiB  
Article
Sustainable Development of Enhanced Luminescence Polymer-Carbon Dots Composite Film for Rapid Cd2+ Removal from Wastewater
by Mohammed Abdullah Issa and Zurina Z. Abidin
Molecules 2020, 25(15), 3541; https://doi.org/10.3390/molecules25153541 - 03 Aug 2020
Cited by 22 | Viewed by 3678
Abstract
As a remedy for environmental pollution, a versatile synthetic approach has been developed to prepare polyvinyl alcohol (PVA)/nitrogen-doped carbon dots (CDs) composite film (PVA-CDs) for removal of toxic cadmium ions. The CDs were first synthesized using carboxymethylcellulose (CMC) of oil palms empty fruit [...] Read more.
As a remedy for environmental pollution, a versatile synthetic approach has been developed to prepare polyvinyl alcohol (PVA)/nitrogen-doped carbon dots (CDs) composite film (PVA-CDs) for removal of toxic cadmium ions. The CDs were first synthesized using carboxymethylcellulose (CMC) of oil palms empty fruit bunch wastes with the addition of polyethyleneimine (PEI) and then the CDs were embedded with PVA. The PVA-CDs film possess synergistic functionalities through increasing the content of hydrogen bonds for chemisorption compared to the pure CDs. Optical analysis of PVA-CDs film was performed by ultraviolet-visible and fluorescence spectroscopy. Compared to the pure CDs, the solid-state PVA-CDs displayed a bright blue color with a quantum yield (QY) of 47%; they possess excitation-independent emission and a higher Cd2+ removal efficiency of 91.1%. The equilibrium state was achieved within 10 min. It was found that adsorption data fit well with the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption uptake was 113.6 mg g−1 at an optimal pH of 7. Desorption experiments showhe that adsorbent can be reused fruitfully for five adsorption-desorption cycles using 0.1 HCl elution. The film was successfully applied to real water samples with a removal efficiency of 95.34% and 90.9% for tap and drinking water, respectively. The fabricated membrane is biodegradable and its preparation follows an ecofriendly green route. Full article
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14 pages, 4991 KiB  
Article
CuFe2O4/Polyaniline (PANI) Nanocomposite for the Hazard Mercuric Ion Removal: Synthesis, Characterization, and Adsorption Properties Study
by Saad S. M. Hassan, Ayman H. Kamel, Amr A. Hassan, Abd El-Galil E. Amr, Heba Abd El-Naby, Mohamed A. Al-Omar and Ahmed Y. A. Sayed
Molecules 2020, 25(12), 2721; https://doi.org/10.3390/molecules25122721 - 12 Jun 2020
Cited by 15 | Viewed by 2699
Abstract
Copper ferrite nano-particles (CuFe2O4) were synthesized, characterized, modified with polyaniline to form CuFe2O4/PANI nano-composite. They were used as new adsorbents for the removal of the hazardous mercuric ions from aqueous solutions. High resolution transmission electron [...] Read more.
Copper ferrite nano-particles (CuFe2O4) were synthesized, characterized, modified with polyaniline to form CuFe2O4/PANI nano-composite. They were used as new adsorbents for the removal of the hazardous mercuric ions from aqueous solutions. High resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Brunauer–Emmett–Teller (BET) were used for the characterization of the synthesized CuFe2O4 nano-particles (NPs) in presence and absence of PANI nano-composite. The synthesized CuFe2O4NPs were of spherical shape with an average size of 10.8 nm. XRD analysis displayed crystal peaks for CuFe2O4NPs and amorphous peaks CuFe2O4/PANI nano-composite due to the existence of polyaniline layer. Contact time, adsorbent dose, solution pH, adsorption kinetics, adsorption isotherm and recyclability were studied. The method at the optimum conditions exhibited high performance with high mercury removal percentage of up to 99% with a maximum adsorption capacity 12.5 and 157.1 mg/g for CuFe2O4 and CuFe2O4/PANI, respectively. The adsorption processes were fitted to Langmuir isotherms. The adsorption behavior of CuFe2O4@PANI composite towards Hg2+ ions is attributed to the soft acid–soft base strong interaction between PANI and Hg(II) ions. High stability and enhanced re-usability are offered using CuFe2O4@PANI composite due to its enhanced removal efficiency. No significant removal decrease was noticed after five adsorption–desorption cycles. In addition, it possesses an easy removal from aqueous solutions by external magnetic field after adsorption experiments. These indicated the enhancement of polyaniline to the surface of CuFe2O4 toward the adsorption of mercury from aqueous solutions. Full article
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15 pages, 6570 KiB  
Article
Stepwise Ethanol-Water Fractionation of Enzymatic Hydrolysis Lignin to Improve Its Performance as a Cationic Dye Adsorbent
by Wenjie Sui, Tairan Pang, Guanhua Wang, Cuiyun Liu, Ashak Mahmud Parvez, Chuanling Si and Chao Li
Molecules 2020, 25(11), 2603; https://doi.org/10.3390/molecules25112603 - 03 Jun 2020
Cited by 18 | Viewed by 2631
Abstract
In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol [...] Read more.
In this work, lignin fractionation is proposed as an effective approach to reduce the heterogeneity of lignin and improve the adsorption and recycle performances of lignin as a cationic dye adsorbent. By stepwise dissolution of enzymatic hydrolysis lignin in 95% and 80% ethanol solutions, three lignin subdivisions (95% ethanol-soluble subdivision, 80% ethanol-soluble subdivision, and 80% ethanol-insoluble subdivision) were obtained. The three lignin subdivisions were characterized by gel permeation chromatography (GPC), FTIR, 2D-NMR and scanning electron microscopy (SEM), and their adsorption capacities for methylene blue were compared. The results showed that the 80% ethanol-insoluble subdivision exhibited the highest adsorption capacity and its value (396.85 mg/g) was over 0.4 times higher than that of the unfractionated lignin (281.54 mg/g). The increased adsorption capacity was caused by the enhancement of both specific surface area and negative Zeta potential. The maximum monolayer adsorption capacity of 80% ethanol-insoluble subdivision by adsorption kinetics and isotherm studies was found to be 431.1 mg/g, which was much higher than most of reported lignin-based adsorbents. Moreover, the 80% ethanol-insoluble subdivision had much higher regeneration yield (over 90% after 5 recycles) compared with the other two subdivisions. Consequently, the proposed fractionation method is proved to be a novel and efficient non-chemical modification approach that significantly improves adsorption capacity and recyclability of lignin. Full article
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15 pages, 3449 KiB  
Article
Porous Activated Carbon from Lignocellulosic Agricultural Waste for the Removal of Acetampirid Pesticide from Aqueous Solutions
by Somaia G. Mohammad, Sahar M. Ahmed, Abd El-Galil E. Amr and Ayman H. Kamel
Molecules 2020, 25(10), 2339; https://doi.org/10.3390/molecules25102339 - 17 May 2020
Cited by 43 | Viewed by 3430
Abstract
A facile eco-friendly approach for acetampirid pesticide removal is presented. The method is based on the use of micro- and mesoporous activated carbon (TPAC) as a natural adsorbent. TPAC was synthesized via chemical treatment of tangerine peels with phosphoric acid. The prepared activated [...] Read more.
A facile eco-friendly approach for acetampirid pesticide removal is presented. The method is based on the use of micro- and mesoporous activated carbon (TPAC) as a natural adsorbent. TPAC was synthesized via chemical treatment of tangerine peels with phosphoric acid. The prepared activated carbon was characterized before and after the adsorption process using Fourier- transform infrared (FTIR), X-ray diffraction (XRD), particle size and surface area. The effects of various parameters on the adsorption of acetampirid including adsorbent dose (0.02–0.2 g), pH 2–8, initial adsorbate concentration (10–100 mg/L), contact time (10–300 min) and temperature (25–50 °C) were studied. Batch adsorption features were evaluated using Langmuir and Freundlich isotherms. The adsorption process followed the Langmuir isotherm model with a maximum adsorption capacity of 35.7 mg/g and an equilibration time within 240 min. The adsorption kinetics of acetamiprid was fitted to the pseudo-second-order kinetics model. From the thermodynamics perspective, the adsorption was found to be exothermic and spontaneous in nature. TPAC was successfully regenerated and reused for three consecutive cycles. The results of the presented study show that TPAC may be used as an effective eco-friendly, low cost and highly efficient adsorbent for the removal of acetamiprid pesticides from aqueous solutions. Full article
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Review

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16 pages, 1231 KiB  
Review
Current Trends in the Application of Nanomaterials for the Removal of Pollutants from Industrial Wastewater Treatment—A Review
by Geetha Palani, A. Arputhalatha, Karthik Kannan, Sivarama Krishna Lakkaboyana, Marlia M. Hanafiah, Vinay Kumar and Ravi Kumar Marella
Molecules 2021, 26(9), 2799; https://doi.org/10.3390/molecules26092799 - 10 May 2021
Cited by 62 | Viewed by 5835
Abstract
In the recent decades, development of new and innovative technology resulted in a very high amount of effluents. Industrial wastewaters originating from various industries contribute as a major source of water pollution. The pollutants in the wastewater include organic and inorganic pollutants, heavy [...] Read more.
In the recent decades, development of new and innovative technology resulted in a very high amount of effluents. Industrial wastewaters originating from various industries contribute as a major source of water pollution. The pollutants in the wastewater include organic and inorganic pollutants, heavy metals, and non-disintegrating materials. This pollutant poses a severe threat to the environment. Therefore, novel and innovative methods and technologies need to adapt for their removal. Recent years saw nanomaterials as a potential candidate for pollutants removal. Nowadays, a range of cost-effective nanomaterials are available with unique properties. In this context, nano-absorbents are excellent materials. Heavy metal contamination is widespread in underground and surface waters. Recently, various studies focused on the removal of heavy metals. The presented review article here focused on removal of contaminants originated from industrial wastewater utilizing nanomaterials. Full article
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22 pages, 1721 KiB  
Review
Treatment of Wastewaters with Zirconium Phosphate Based Materials: A Review on Efficient Systems for the Removal of Heavy Metal and Dye Water Pollutants
by Monica Pica
Molecules 2021, 26(8), 2392; https://doi.org/10.3390/molecules26082392 - 20 Apr 2021
Cited by 24 | Viewed by 3932
Abstract
Layered zirconium phosphate (ZrP) is a versatile material with phosphate (POH ) groups able to exchange inorganic and organic cations or to intercalate basic molecules. The present review deals with the use of this material as a sorbent for heavy metal cations or [...] Read more.
Layered zirconium phosphate (ZrP) is a versatile material with phosphate (POH ) groups able to exchange inorganic and organic cations or to intercalate basic molecules. The present review deals with the use of this material as a sorbent for heavy metal cations or dye molecules in wastewater treatments. The possibility to combine ZrP with polymers or other inorganic materials, in order to have suitable systems for real and large scale applications, was investigated, as well as the combination with photocatalytic materials to obtain hetrogeneous photocatalysts for the capture and photodegradation of organic dye molecules. Full article
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45 pages, 2710 KiB  
Review
Recent Developments in Chitosan-Based Adsorbents for the Removal of Pollutants from Aqueous Environments
by Daniele C. da Silva Alves, Bronach Healy, Luiz A. de Almeida Pinto, Tito R. Sant’Anna Cadaval, Jr. and Carmel B. Breslin
Molecules 2021, 26(3), 594; https://doi.org/10.3390/molecules26030594 - 23 Jan 2021
Cited by 151 | Viewed by 9395
Abstract
The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have [...] Read more.
The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have the potential to remove many of these contaminants. In this review the development of chitosan-based adsorbents is described and discussed. Following a short introduction to the extraction of chitin from seafood wastes, followed by its conversion to chitosan, the properties of chitosan are described. Then, the emerging chitosan/carbon-based materials, including magnetic chitosan and chitosan combined with graphene oxide, carbon nanotubes, biochar, and activated carbon and also chitosan-silica composites are introduced. The applications of these materials in the removal of various heavy metal ions, including Cr(VI), Pb(II), Cd(II), Cu(II), and different cationic and anionic dyes, phenol and other organic molecules, such as antibiotics, are reviewed, compared and discussed. Adsorption isotherms and adsorption kinetics are then highlighted and followed by details on the mechanisms of adsorption and the role of the chitosan and the carbon or silica supports. Based on the reviewed papers, it is clear, that while some challenges remain, chitosan-based materials are emerging as promising adsorbents. Full article
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16 pages, 1930 KiB  
Review
Extremophilic Microorganisms for the Treatment of Toxic Pollutants in the Environment
by Sun-Wook Jeong and Yong Jun Choi
Molecules 2020, 25(21), 4916; https://doi.org/10.3390/molecules25214916 - 23 Oct 2020
Cited by 24 | Viewed by 5786
Abstract
As concerns about the substantial effect of various hazardous toxic pollutants on the environment and public health are increasing, the development of effective and sustainable treatment methods is urgently needed. In particular, the remediation of toxic components such as radioactive waste, toxic heavy [...] Read more.
As concerns about the substantial effect of various hazardous toxic pollutants on the environment and public health are increasing, the development of effective and sustainable treatment methods is urgently needed. In particular, the remediation of toxic components such as radioactive waste, toxic heavy metals, and other harmful substances under extreme conditions is quite difficult due to their restricted accessibility. Thus, novel treatment methods for the removal of toxic pollutants using extremophilic microorganisms that can thrive under extreme conditions have been investigated during the past several decades. In this review, recent trends in bioremediation using extremophilic microorganisms and related approaches to develop them are reviewed, with relevant examples and perspectives. Full article
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21 pages, 1010 KiB  
Review
Application Research of Biochar for the Remediation of Soil Heavy Metals Contamination: A Review
by Sheng Cheng, Tao Chen, Wenbin Xu, Jian Huang, Shaojun Jiang and Bo Yan
Molecules 2020, 25(14), 3167; https://doi.org/10.3390/molecules25143167 - 10 Jul 2020
Cited by 86 | Viewed by 8714
Abstract
Soil contamination by heavy metals threatens the quality of agricultural products and human health, so it is necessary to choose certain economic and effective remediation techniques to control the continuous deterioration of land quality. This paper is intended to present an overview on [...] Read more.
Soil contamination by heavy metals threatens the quality of agricultural products and human health, so it is necessary to choose certain economic and effective remediation techniques to control the continuous deterioration of land quality. This paper is intended to present an overview on the application of biochar as an addition to the remediation of heavy-metal-contaminated soil, in terms of its preparation technologies and performance characteristics, remediation mechanisms and effects, and impacts on heavy metal bioavailability. Biochar is a carbon-neutral or carbon-negative product produced by the thermochemical transformation of plant- and animal-based biomass. Biochar shows numerous advantages in increasing soil pH value and organic carbon content, improving soil water-holding capacity, reducing the available fraction of heavy metals, increasing agricultural crop yield and inhibiting the uptake and accumulation of heavy metals. Different conditions, such as biomass type, pyrolysis temperature, heating rate and residence time are the pivotal factors governing the performance characteristics of biochar. Affected by the pH value and dissolved organic carbon and ash content of biochar, the interaction mechanisms between biochar and heavy metals mainly includes complexation, reduction, cation exchange, electrostatic attraction and precipitation. Finally, the potential risks of in-situ remediation strategy of biochar are expounded upon, which provides the directions for future research to ensure the safe production and sustainable utilization of biochar. Full article
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