Application of Response Surface Design for Optimization of Direct Red Dye Biosorption onto Cockleshells

Abstract

This work emphasizes the efficiency of the response surface design to optimize the parameters affecting the removal of a textile dye—Direct Red 81 (DR-81)—by biosorption on seafood waste, namely, cockleshells (CS). The adsorbent was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis of surface and pH points of zero charge (pHpzc). A Box–Behnken design (BBD) with three factors was used to optimize the experimental conditions. After the experiment and data analysis, the optimal conditions found were 1 g of adsorbents, 10 mg/L of initial dye concentration, and a pH of 2 in the adsorbate solution, with the highest removal efficiency of 99.98%. The experimental results were analyzed by the ANOVA test, and they demonstrated the acceptability of the quadratic regression model. The adjusted determination coefficient R2 (adj) was equal to 98.82%, indicating an excellent relationship between the predicted and experimental responses. Langmuir isotherms were determined to be the best-fitting model, and the maximum adsorption capacity was 4.65 mg/g. The adsorption process was endothermic and fit the pseudo-second-order model. The negative values of ∆H and ∆S in the thermodynamic research showed that the bio-adsorption technique for the removal of Direct Red 81 is exothermic, spontaneous, and feasible. In addition, the negative value of ∆G indicates that the adsorption mechanism occurs at solid–liquid interfaces with an increasing number of species.

Valorization of Pine Cones (Pinus nigras) for Industrial Wastewater Treatment and Crystal Violet Removal: A Sustainable Approach Based on Bio-Coagulants and a Bio-Adsorbent

“…A solution of crystal violet (CV) was prepared with concentrations varying from 20 mg/L to 70 mg/L and was adjusted to different pH values (4)(5)(6)(7)(8)(9)(10). Different doses of the adsorbent (20-200 mg/L) were added to each solution, and the solutions were agitated for 20-120 min at a constant speed of 200 rpm at room temperature.…”

“…It could be easily inferred that the percent removal of CV increased with an increasing amount of the adsorbent (20-200 mg), as shown in Figure 10c,e,f, as we could see a stronger response (75%) with a higher amount of the adsorbent. This was due to the greater availability of the exchangeable sites or surface area at higher concentrations of the adsorbent [9].…”

“…It could be easily inferred that the percent removal of CV increased with an increasing amount of the adsorbent (20-200 mg), as shown in Figure 10c,e,f, as we could see a stronger response (75%) with a higher amount of the adsorbent. This was due to the greater availability of the exchangeable sites or surface area at higher concentrations of the adsorbent [9]. The analysis of variance (ANOVA) is essential to test the significance of the quadratic response surface regression model using Minitab software 21.1.0 (LLC, State College, PA, USA).…”

“…Treating food processing wastewater before discharging it into coastal waters, rivers, and lakes is essential to reduce the risk of environmental pollution [7]. On the other hand, synthetic dyes are a significant class of recalcitrant organic compounds that are frequently found in the environment because of their widespread use in several industries such as the textile industry [8,9]. Increased demand and applications of synthetic dyes in chemical-based industries has led to the discharge of highly polluted wastewater, resulting in health problems and environmental pollution [10].…”

Removal of Chromium (VI) from Water Using Orange peel as the Biosorbent: Experimental, Modeling, and Kinetic Studies on Adsorption Isotherms and Chemical Structure

“…The flasks were kept closed at room temperature for 48 h, and then the final pH (pH f ) was determined. On the graph of pH f = f(pHi), the intersection of the curve with the quadrant bisector represents the iso-electric point (pH pzc ) [41,42].…”