Design and modeling of the decolorization characteristics of a regenerable and eco-friendly geopolymer: Batch and dynamic flow mode treatment aspects.

Abstract One of the most important environmental and health issues today is the elimination of the dye pollution from the contaminated water ecosystem. The use of geopolymers to eliminate such contaminants has recently emerged as a promising alternative. In this study, metakaolin based geopolymer (MKBG) was synthesized to be a promising adsorbent for Basic Blue 7 (BB7). To optimize the input parameters (solution pH, MKBG dose, mixing time, temperature, mixing speed, column diameter, and flow rate) towards BB7 removal by MKBG, a Box-Behnken design (BBD) was employed to develop the response model, followed by numerical optimization. The quadratic models correlating the adsorption variables to BB7 adsorption yield as responses were developed for batch and dynamic flow systems. The pseudo-second-order model accurately predicted the BB7 adsorption kinetics on MKBG. Decolorization yields of BB7 in batch and continuous systems reached 96 % and 56 %, respectively. The Langmuir model accurately described equilibrium data, thereby justifying monolayer and homogeneous adsorption. The MKBG demonstrated significant reusability up to 20 dynamic flow adsorption cycles. IR, SEM, and zeta potential measurements were used to describe the sorbent structure, and the mechanism of MKBG-BB7 interaction was assessed. Overall, MKBG offers a good application potential for the treatment of basic dye contaminated waters.