Performance evaluation of treated adsorbents derived from agricultural waste towards adsortion of azo dyes

Abstract

Wastewaters generated from the industries contain large amounts of azo dyes which, owning to their non-biodegradability, toxicity and potential carcinogenic nature, constitute a major threat to the surrounding ecosystem. In this study I used coconut coir (waste biomass) as a raw material to produce potential adsorbent in adsorption of azo dyes. Three samples of adsorbent prepared through physical and chemical treatment; raw, treated and pyrolysed being compared to evaluate their adsorption performance. Batch mode experiments were conducted to assess the potential for the removal of Methylene blue and Acid orange 7 dyes from aqueous solution model using the above adsorbent. Sorption isotherm and kinetic studies have been done by varying the parameters like initial concentration of dyes solution, and varying the contact time. The Langmuir isotherm model shows maximum adsorption capacity (qm) for MB is higher than AO7. Chemical treatment sample shows better qm followed by pyrolysed and raw. Freundlich isotherm model shows 1/n for both MB and AO7 are favorable for adsorption except for raw sample. The Lagergren kinetic model shows R2 for pyrolyed sample is better than treated followed by raw sample. While Pseudo second order shows R2 for all samples is better than Lagergren result. The pyrolysed sample was characterized by Scanning Electron Microscope (SEM) and Brunauer–Emmett–Teller (BET).