Fabrication of ZnO decorated porous chitosan beads for the sustainable bioremediation of Cr(VI) contaminated water

Chromium contamination, particularly in industrial and mining sectors, has become a serious issue for the aquatic system, globally. Until now, the removal of Cr(VI) have been accomplished by a variety of approaches. However, these existing techniques are economically not efficient. Here, we demonstrate quick and effective removal of Cr(VI) from water by biosorption method using simple polymer modification technique. Specifically, we synthesized native chitosan beads (NCB) and ZnO NPs modified chitosan beads (ZMCB) for the adsorptive elimination of Cr(VI) from aqueous medium. Some advanced analytical techniques such as BET, SEM-EDX, XRD and FTIR were applied to characterize the biosorbents. Both NCB and ZMCB followed Langmuir isotherm model and maximum adsorption capacity of 23.16 mg/g and 130.28 mg/g, respectively was observed at optimal conditions (1.5 g dose, pH 2, initial concentration 50 ppm at 293 K). The results showed that pseudo 2nd order (PSO) kinetic was best fitted for the biosorption process, as coefficient regression constant for PSO have highest value (R2 > 0.999). Additionally, it was observed that the ZMCB composite may be used in many Cr(VI) adsorption cycles with little decrease in adsorption efficiency (91% adsorption up to the 5th cycle). Overall, this study offers a quick and easy approach for synthesizing low-cost materials that will be extremely useful for environmental applications.