Effective single and contest carcinogenic dyes adsorption onto A-zeolite/bacterial cellulose composite membrane: Adsorption isotherms, kinetics, and thermodynamics

Abstract

This study reports loading of A-zeolite particles on the bacterial cellulose membrane for single and binary carcinogenic dye uptake from the aqueous solution. The bio based membrane was obtained using Gluconobacter Oxydans NRRL 759 in liquid culture medium. Meanwhile, the incorporation of zeolite particles within the bacterial cellulose matrix and on its surface was implemented via in-situ synthesis. The crystallite structure and the morphology of obtained composite membrane were characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM) hyphenated with energy dispersive X-ray (EDX). The surface characteristics were intensively investigated by N2 adsorption/desorption isotherm, SBET, pore size distribution, and zeta potential. The results indicate that the treatment of bacterial cellulose with zeolite particles reflected two folds in surface area and three folds in the point of zero charge (pHzpc 6.7) compared with un-modified one. The produced composite membrane was also examined against removal of sole cationic methylene blue "MB", and anionic Congo-Red "CR" or in binary solutions included "MB" with Malachite green "MG" or "CR" with different percentages through batch adsorption technique. Different parameters affecting the adsorption process, such as dye concentration, adsorbent type, contact time, temperature, and pH, were optimized. The highest removal was recorded at optimum conditions for sole "MB" dye (99.2%), "CR" dye (81%), binary mixed "2MB/1CR" (96% after 15 min, 91% after 12 h, respectively), and "2MB/1MG" (98.6% after 30 min). Moreover, linear and nonlinear adsorption isotherm models confirmed that MB adsorption and CR obeys Freundlich isotherm model. Also, the kinetic studies revealed that the dyes' adsorption on the composite membrane could be clarified using linear and nonlinear forms of pseudo-first order, pseudo-second order, and intra-particle diffusion models. Thermodynamic findings emphasized the endothermic and spontaneous adsorption process as the adsorbent/ adsorbate physical interaction decreased the entropy. Eventually, the recyclability test revealed that the composite matrix exhibits excellent removal efficiency up to 5 recycles. The primary adsorption mechanism was proposed and confirmed with Fourier transform infrared (FTIR). Finally, the unprecedented composite membrane can be considered as an economically distinguished adsorbent for the removal of not only sol dyes but also mixtures of anionic and cationic dyes.