Efficiency of a novel synthesised material for the treatment of a binary heavy metal system

High levels of heavy metal ions in wastewater pose significant challenges in the world, originating from both natural and anthropogenic sources. Among the effective techniques for removing heavy metal ions from various water sources, the adsorption process using natural and environmentally friendly materials stands out. In this work, a biocomposite obtained from the bio-treatment of geopolymer using chitosan was used for the effective removal of nickel and arsenic from a synthesised binary wastewater system using batch experiments. The adsorption process was significantly influenced by factors such as pH, adsorbent mass, adsorbent mass and metal ion concentrations. The maximum adsorption capacities for nickel and arsenic were determined to be $45.686 mg/g$ and $59.580 mg/g$⁠, respectively, which were achieved at a pH of 7.66, a contact time of 53 min, a metal ion concentration of $100 mg/l$⁠, an adsorbent dosage of $0.1 g$ and without biopolymer treatment. Four different isotherm models were used to evaluate the experimental data and it was found that the non-modified competitive Langmuir isotherm gave the best fit based on the Marquardt percentage standard deviation. Based on the reaction kinetics, the pseudo-second-order reaction model was the best for describing nickel adsorption process, while the pseudo-first-order model and the intraparticle diffusion model were the best for the arsenic adsorption process. Fourier transform infrared spectrometry and scanning electron microscopy analyses demonstrated the microstructural changes that undergirded the successful removal of nickel ion and arsenic ion using the novel material.