Effective sorption of hexavalent chromium by chemically improved bio-debris – Statistical, isothermal and kinetic evaluations

Abstract

Chromium in its hexavalent state (Cr(VI)) is of significant environmental concern due to its persistence, non-biodegradability, and bioaccumulation, leading to severe health issues in living organisms. Cr(VI) salts are extensively utilized in various industries, including plating, dyeing, tanning, stainless steel manufacturing, and thermal spraying. This study investigates the sorption potential of Artabotrys hexapetalus Seeds (AHS) for removing chromium from aqueous solutions prepared from potassium dichromate salts, where, chromium is in hexavalent state. An acid treatment process is conducted to enhance the seed's surface properties and adsorption efficiency. The study assesses the physio-chemical attributes of the treated AHS (TAHS) through standard analytical methods, including BET/BJH surface area measurement, microscopic analysis, FTIR, SEM/EDAX and TG-DTA. Characterization focuses on surface characteristics, functional group alterations, morphological changes, elemental composition, and thermal stability of TAHS, during the sorption process. Sorption capacity of TAHS is determined via Batch method, by optimizing parameters such as particle size (0.18 mm), initial Cr(VI) concentration (200 mg/L), dosage (300 mg), and pH (5). Atomic Absorption Spectrophotometer studies on pre- and post-sorption samples reveal a 94% removal of Cr(VI). Additional investigations on cationic, anionic, and co-ionic interactions further validate the laboratory results for potential industrial applications. Desorption and regeneration studies confirm that TAHS can be reused effectively upto three cycles. Statistical analyses indicate 95% significance in the findings. The sorption mechanism is modeled through both linear and non-linear isothermal and kinetic analyses, revealing a linear alignment to the Langmuir model and adherence to pseudo-second-order kinetics. Overall, the study confirms the efficacy of TAHS in removing Cr(VI) ions from laboratory solutions, suggesting its potential applicability in real-world scenarios.