# Optimization of MCM-41 Mesoporous Material Mixed Matrix Polyethersulfone Membrane for Dye Removal

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

^{−2}·h

^{−1}·bar

^{-1}) and 63.16 (L·m

^{−2}·h

^{−1}·bar

^{-1}) for the AB-210 and RB dyes, respectively. An MCM-41 content of nearly 0.8 wt.% in the casting solution, feed dye concentration of 10 ppm for the studied dyes, and feed pH of 3 for the RB dye was found to be the optimal parameters for eliciting the response. The pH had no significant influence on the response for the AB-210 dye, while the pH shows some minor effects on response with the RB dye, and the Pareto chart of the standardized effects on the permeation flux of both dyes using statistically significant at the 5% significance level support these results.

## 1. Introduction

_{34}H

_{25}Na

_{2}N

_{11}O

_{11}S

_{3}) and rose bengal (C

_{20}H

_{2}Cl

_{4}l

_{4}Na

_{2}O

_{5}) are examples of anionic dyes that are widely used to alter the color of a solution, and extensive physical, chemical, and biological methodologies have been suggested to remove such dyes from wastewater [3,4,5].

## 2. Experimental Work

#### 2.1. Materials

^{®}, with an average MW = 30,000 g mol

^{−1}) donated by Solvay Advanced Polymers (Brussels, Belgium). Dimethyl sulfoxide (DMSO, (CH

_{3})

_{2}SO, MW = 78.13 g mol

^{−1}) was the polymer solvent, obtained from Sigma-Aldrich (St. Louis, MO, USA). Acid black 210 (AB-210, C

_{34}H

_{25}N

_{11}Na

_{2}O

_{11}S

_{3}, MW = 938.02 g mol

^{−1}) and rose bengal (RB, C

_{20}H

_{2}Cl

_{4}I

_{4}Na

_{2}O

_{5}, MW = 1017.64 g mol

^{−1}), were obtained from local markets (Baghdad, Iraq).

#### 2.2. Preparation of Composite Membranes

#### 2.3. Membranes Characteristics

_{1}and W

_{2}are the weights of the wet and dry membranes (g), respectively; A is the effective membrane area (cm

^{2}); T is the membrane thickness (μm); and ρ is the water density (0.998 g/cm

^{3}at 25 °C). Prior to measurements, the membrane samples of pristine and fabricated PES membranes were immersed in deionized water for 24 h at room temperature. After the water was wiped from the membranes, they were weighed. To estimate the average porosity of the membranes, triplicates of each sample were tested.

^{3}) having an effective membrane area of 16 cm

^{2}(Scheme 1). First, each membrane sample was pressurized for 20 min at 4 bar to compact the membranes before the filtration tests. The pressure was then lowered to the operating pressure of 3 bars at 25 ± 1 °C, and the water permeability magnitudes were recorded. According to what was found in the literature for the concentration of dyes in wastewater [1,2], the separation tests were evaluated under four concentrations (i.e., 10, 50, 80, and 100 ppm) of aqueous solutions for each of the AB-210 and RB dyes. The pure water permeability was determined according to the following equation:

^{−2}·hr

^{−1}·bar

^{−1}), V is the volume of the collected permeate (L), t is the time the permeate was collected (h), A is the membrane surface area (m

^{2}), and ΔP is the operational pressure (bar).

## 3. Results and Discussion

## 4. Optimization and Modeling Process

#### 4.1. Optimization of Operating Parameters

^{®}17. Due to their better membrane performance, the modified PES/MCM-41 flat sheets utilized in this process had a 58.6° contact angle under 3 bar pressure. The developed optimization design for membrane permeability response was verified statistically via the analysis of variance (ANOVA) technique, which presented good coefficient of determination values, R

^{2}= 0.8828 and 0.8868, for AB-210 and RB dyes, respectively. Table 3 illustrates the experimental codes of various parameters, indicating either low or high levels after their units. To avoid any methodological error in the optimization design, a random distribution was used, which facilitated obtaining optimal values of the operating variables for the NF process.

#### 4.2. ANOVA Models

^{®}17, with a level of significance of 5% needed to consider a variable necessary to the operational process. Table 4 indicates the ANOVA results for the permeability as a function of the MCM-41 weight ratios, dye concentrations, and feed pH values. In the ANOVA table, there is a p-value for each independent variable in the design. When the p-value is less than 5%, the variables are statistically significant [38].

#### 4.3. Evaluating and Analyzing Results

#### 4.3.1. Effect Plot

#### 4.3.1.1. Pareto Chart

#### 4.3.1.2. Main Effects Plot

#### 4.3.1.3. Interaction Plot

#### 4.3.2. Residual Plot

#### 4.3.2.1. Normal Probability Plot of Residuals

#### 4.3.2.2. Residuals Versus Order and Fits Plot

#### 4.3.3. Response Surface Analysis

#### 4.4. Optimization of the NF Membrane Permeability

^{®}17 computer software. The optimization results are shown in the left column, while the optimum value for each variable is illustrated in the center of the top row (in red).

^{−2}.h

^{−1}. It can be concluded that the primary factor in this process is that MCM-41 weight ratios had been added to the casting solution, followed by the secondary factor, dye concentrations. As indicated by the presence of a horizontal line, the feed pH values had no significant influence on the permeability.

^{−2}.h

^{−1}. As with the AB-210 dye, the principal factor in this process was the added MCM-41 weight ratios in the casting solution, followed by the dye concentrations as the secondary factor. When a line has a small deflection from the horizontal, as does the line for the pH, it can affect the response. The pH value had a lesser impact on the permeability than the other factors as signified by the less steep slope of the line.

## 5. Conclusions

^{-2}.h

^{-1}.bar

^{-1}for the AB-210 and RB dyes, respectively, was achieved.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Pareto chart of the standardized effects of three parameters—pH (A), concentration (B), and MCM-41 wt.% (C)—on the permeability of (

**a**) AB-210, and (

**b**) RB dyes.

**Figure 2.**Main effect plot of the pH, concentration, and MCM-41 wt.% on the permeability of (

**a**) AB—210, and (

**b**) RB dyes.

**Figure 3.**Interaction plots of the pH, concentration, and MCM-41 wt.% on the permeability of (

**a**) AB—210, (

**b**) RB dyes.

**Figure 4.**Normal probability plot of the residuals for the permeability of (

**a**) AB—210, and (

**b**) RB dyes.

**Figure 5.**Residuals versus the observation orders and fitted values plot for the permeability of (

**a**) AB-210, and (

**b**) RB dyes.

**Figure 6.**Three-dimensional response surface plot (

**A**,

**B**), and two-dimensional response contour plot (

**C**,

**D**) of the permeability as a function of the MCM-41 weight ratio, feed pH, and dye concentration for AB-210 dye.

**Figure 7.**Three-dimensional response surface plot (

**A**,

**B**), and two-dimensional response contour plot (

**C**,

**D**) of the permeability as a function of the MCM-41 weight ratio, feed pH, and dye concentration for RB dye.

**Figure 8.**Optimization plot of the process parameters for the maximum permeability for (

**a**) AB-210, and (

**b**) RB dyes.

Membrane Code | Casting Solution Compositions (wt.%) | Solvents (DMSO) (wt.%) | |
---|---|---|---|

PES | MCM-41 | ||

M0 | 21 | 0 | 79 |

M1 | 21 | 0.1 | 79.9 |

M2 | 21 | 0.3 | 79.7 |

M3 | 21 | 0.5 | 79.5 |

M4 | 21 | 0.7 | 79.3 |

M5 | 21 | 0.8 | 79.2 |

M6 | 21 | 1 | 78 |

**Table 2.**Effect of MCM-41 wt.% on the porosity, water contact angle, and water permeability of PES membranes.

Membrane Code | Thickness * (µm) | Porosity (%) | Average Contact Angle (°) | Pure WATER Permeability (LMH/bar) |
---|---|---|---|---|

M0 | 151.12 ± 2.46 | 26.06 ± 1.25 | 69.2 ± 3.80 | 10 |

M1 | 143.69 ± 1.19 | 66.90 ± 0.63 | 49.1 ± 2.09 | 15 |

M2 | 128.61 ± 2.35 | 68.20 ± 1.00 | 45.2 ± 2.50 | 38.37 |

M3 | 119.83 ± 1.06 | 82.80 ± 0.51 | 40.5 ± 0.50 | 77.8 |

M4 | 95.55 ± 1.22 | 73.20 ± 0.38 | 52.0 ± 1.60 | 65.2 |

M5 | 91.20 ± 0.79 | 75.76 ± 0.47 | 58.6 ± 0.97 | 66.5 |

M6 | 87.99 ± 1.11 | 76.60 ± 0.91 | 59.1 ± 1.01 | 70 |

Parameters | Code | Units | Low level | High Level |
---|---|---|---|---|

MCM-41 content | X1 | wt.% | 0 | 1 |

AB 210 dye concentration | X2 | ppm | 10 | 100 |

RB dye concentration | X3 | ppm | 10 | 100 |

pH of dye solution | X4 | - | 3 | 11 |

permeability | Y | LMH/bar | Target |

Source | DF | Adj SS | Adj MS | F-Value | p-Value | |||

Model | 8 | 13,166.7 | 1645.84 | 36.70 | 0.000 | |||

Linear | 3 | 9347.7 | 3115.91 | 69.49 | 0.000 | |||

pH | 1 | 155.3 | 155.32 | 3.46 | 0.070 | |||

Concentration | 1 | 1417.1 | 1417.11 | 31.60 | 0.000 | |||

% MCM-41 | 1 | 7680.8 | 7680.85 | 171.29 | 0.000 | |||

Square | 3 | 2825.2 | 941.74 | 21.00 | 0.000 | |||

pH × pH | 1 | 4.9 | 4.86 | 0.11 | 0.744 | |||

Dye conc., ppm × Dye conc.,ppm | 1 | 2.0 | 2.03 | 0.05 | 0.833 | |||

% MCM-41 × % MCM-41 | 1 | 2638.6 | 2638.55 | 58.84 | 0.000 | |||

2-Way Interaction | 2 | 137.6 | 68.78 | 1.53 | 0.228 | |||

pH × conc. | 1 | 52.3 | 52.34 | 1.17 | 0.287 | |||

Conc. × % MCM-41 | 1 | 83.5 | 83.51 | 1.86 | 0.180 | |||

Error | 39 | 1748.8 | 44.84 | |||||

Lack-of-Fit | 35 | 1748.8 | 49.96 | |||||

Pure Error | 4 | 0.0 | 0.00 | |||||

Total | 47 | 14,915.5 | ||||||

S | R-sq | R-sq(adj) | R-sq(pred) | (a) AB 210 dye | ||||

6.69627 | 88.28% | 85.87% | 83.95% | |||||

Source | DF | Adj SS | Adj MS | F-Value | p-Value | |||

Model | 8 | 12,533.6 | 1566.70 | 38.17 | 0.000 | |||

Linear | 3 | 9390.0 | 3130.01 | 76.26 | 0.000 | |||

pH | 1 | 245.9 | 245.90 | 5.99 | 0.019 | |||

Concentration | 1 | 1610.5 | 1610.54 | 39.24 | 0.000 | |||

% MCM-41 | 1 | 7408.6 | 7408.56 | 180.51 | 0.000 | |||

Square | 3 | 2402.6 | 800.88 | 19.51 | 0.000 | |||

pH × pH | 1 | 7.6 | 7.57 | 0.18 | 0.670 | |||

Dye conc., ppm × Dye conc.,ppm | 1 | 1.3 | 1.28 | 0.03 | 0.861 | |||

% MCM-41 × % MCM-41 | 1 | 2226.4 | 2226.41 | 54.25 | 0.000 | |||

2-Way Interaction | 2 | 184.1 | 92.06 | 2.24 | 0.120 | |||

pH × conc. | 1 | 75.6 | 75.57 | 1.84 | 0.183 | |||

conc. × % MCM-41 | 1 | 106.2 | 106.24 | 2.59 | 0.116 | |||

Error | 39 | 1600.7 | 41.04 | |||||

Lack-of-Fit | 35 | 1599.7 | 45.71 | 186.55 | 0.000 | |||

Pure Error | 4 | 1.0 | 0.24 | |||||

Total | 47 | 14,134.2 | ||||||

S | R-sq | R-sq(adj) | R-sq(pred) | (b) RB dye | ||||

6.40645 | 88.68% | 86.35% | 84.43% |

(a) AB 210 Dye | |||||||||

Coded Coefficients | |||||||||

Term | Coef | SE Coef | T-Value | p-Value | VIF | ||||

Constant | 45.28 | 2.32 | 19.49 | 0.000 | |||||

pH | −3.70 | 1.99 | −1.86 | 0.070 | 1.14 | ||||

Concentration | −8.29 | 1.47 | −5.62 | 0.000 | 1.32 | ||||

% MCM-41 | 24.45 | 1.87 | 13.09 | 0.000 | 1.03 | ||||

pH × pH | 1.12 | 3.40 | 0.33 | 0.744 | 1.09 | ||||

Conc. × Conc. | −0.48 | 2.24 | −0.21 | 0.833 | 1.00 | ||||

% MCM-41 × % MCM-41 | −21.42 | 2.79 | −7.67 | 0.000 | 1.16 | ||||

pH × Conc. | −2.67 | 2.47 | −1.08 | 0.287 | 1.34 | ||||

Conc. × % MCM-41 | −3.33 | 2.44 | −1.36 | 0.180 | 1.02 | ||||

Fits and Diagnostics for Unusual Observations | |||||||||

Obs | permeability | Fit | Resid | Std Resid | |||||

23 | 25.00 | 39.35 | −14.35 | −2.31 | R | ||||

30 | 21.40 | 34.82 | −13.42 | −2.10 | R | ||||

37 | 17.00 | 30.94 | −13.94 | −2.15 | R | ||||

44 | 14.30 | 28.11 | −13.81 | −2.19 | R | ||||

(b) RB Dye | |||||||||

Term | Coef | SE Coef | T-Value | p-Value | VIF | ||||

Constant | 42.06 | 2.22 | 18.92 | 0.000 | |||||

pH | −4.65 | 1.90 | −2.45 | 0.019 | 1.14 | ||||

Concentration | −8.84 | 1.41 | −6.26 | 0.000 | 1.32 | ||||

% MCM-41 | 24.02 | 1.79 | 13.44 | 0.000 | 1.03 | ||||

pH × pH | 1.40 | 3.25 | 0.43 | 0.670 | 1.09 | ||||

Conc. × Conc. | −0.38 | 2.14 | −0.18 | 0.861 | 1.00 | ||||

% MCM-41 × % MCM-41 | −19.68 | 2.67 | −7.37 | 0.000 | 1.16 | ||||

pH × Conc. | −3.21 | 2.37 | −1.36 | 0.183 | 1.34 | ||||

Conc. × % MCM-41 | −3.76 | 2.33 | −1.61 | 0.116 | 1.02 | ||||

Fits and Diagnostics for Unusual Observations | |||||||||

Obs | permeability | Fit | Resid | Std Resid | |||||

23 | 22.00 | 37.33 | −15.33 | −2.58 | R | ||||

30 | 19.70 | 32.61 | −12.91 | −2.11 | R | ||||

37 | 16.00 | 28.68 | −12.68 | −2.05 | R | ||||

44 | 13.10 | 25.87 | −12.77 | −2.12 | R |

Response Optimization: permeability (L.m^{−2}.hr^{−1}.bar^{−1}) | (a) AB 210 dye | ||||||||||||||||||

Parameters | |||||||||||||||||||

Response | Goal | Lower | Target | Upper | Weight | Importance | |||||||||||||

permeability | Maximum | 4.9 | 62 | 1 | 1 | ||||||||||||||

Solution | |||||||||||||||||||

Solution | pH | Concentration | % MCM-41 | permeability Fit | Composite Desirability | ||||||||||||||

1 | 3 | 10 | 0.828 | 64.2501 | 1 | ||||||||||||||

Multiple Response Prediction | |||||||||||||||||||

Variable | Setting | ||||||||||||||||||

pH | 3 | ||||||||||||||||||

Concentration | 10 | ||||||||||||||||||

% MCM-41 | 0.828 | ||||||||||||||||||

Response | Fit | SE Fit | 95% CI | 95% PI | |||||||||||||||

permeability | 64.25 | 4.52 | (55.11; 73.39) | (47.91; 80.59) | |||||||||||||||

Response Optimization: permeability (L.m^{−2}.hr^{−1}.bar^{−1}) | (b) RB dye | ||||||||||||||||||

Parameters | |||||||||||||||||||

Response | Goal | Lower | Target | Upper | Weight | Importance | |||||||||||||

permeability | Maximum | 4.3 | 60.5 | 1 | 1 | ||||||||||||||

Solution | |||||||||||||||||||

Solution | pH | Conc. | % MCM-41 | permeability Fit | Composite Desirability | ||||||||||||||

1 | 3 | 10 | 0.848 | 63.16 | 1 | ||||||||||||||

Multiple Response Prediction | |||||||||||||||||||

Variable | Setting | ||||||||||||||||||

pH | 3 | ||||||||||||||||||

Concentration | 10 | ||||||||||||||||||

% MCM-41 | 0.848 | ||||||||||||||||||

Response | Fit | SE Fit | 95% CI | 95% PI | |||||||||||||||

permeability | 63.16 | 4.41 | (54.23; 72.08) | (47.42; 78.89) |

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Kadhim, R.J.; Al-Ani, F.H.; Alsalhy, Q.F.; Figoli, A.
Optimization of MCM-41 Mesoporous Material Mixed Matrix Polyethersulfone Membrane for Dye Removal. *Membranes* **2021**, *11*, 414.
https://doi.org/10.3390/membranes11060414

**AMA Style**

Kadhim RJ, Al-Ani FH, Alsalhy QF, Figoli A.
Optimization of MCM-41 Mesoporous Material Mixed Matrix Polyethersulfone Membrane for Dye Removal. *Membranes*. 2021; 11(6):414.
https://doi.org/10.3390/membranes11060414

**Chicago/Turabian Style**

Kadhim, Rana J., Faris H. Al-Ani, Qusay F. Alsalhy, and Alberto Figoli.
2021. "Optimization of MCM-41 Mesoporous Material Mixed Matrix Polyethersulfone Membrane for Dye Removal" *Membranes* 11, no. 6: 414.
https://doi.org/10.3390/membranes11060414