Enhanced removal of Cu(II) and Ni(II) using MnOx-modified non-edible biochar: synthesis, characterization, optimization, thermo-kinetics, and regeneration

Abstract

The remediation of copper and nickel heavy metals from industrial effluents is crucial to prevent environmental pollution and protect public health. Biosorption, a low-cost and eco-friendly technology, has gained increasing attention as an efficient method for the removal of heavy metals from effluent. In this work, a novel low-cost cocopeat biochar has been developed with appropriate chemical modification using KMnO4 to achieve high removal capacity and cyclic stability. Response surface methodology (RSM) was employed to identify optimal conditions and achieved as 1 g/L adsorbent dosage, 710 mg/L metal concentration, and 20-min contact time for Cu(II), and 2.85 g/L adsorbent dosage, 872 mg/L metal concentration, and 20 min contact time for Ni(II). A maximum adsorption capacity achieved as 291.54 mg/g and 181.16 mg/g for Cu(II) and Ni(II), respectively. Biosorbent exhibited a rapid kinetic process, with 86.44% and 77.61% adsorption occurring within just 20 min for Cu(II) and Ni(II), respectively. Brunauer–Emmett–Teller (BET) analysis showed a well-developed mesoporous molecular structure with an average pore diameter of 42.593 nm. The experimental results were fitted well with the pseudo-second-order and Langmuir isotherm, indicating monolayer adsorption primarily directed by chemisorption. Desorption efficiencies 48.25% and 52.16% for Cu(II) and Ni(II) respectively were achieved after four adsorption–desorption cycles. Furthermore, a preliminary study of chitosan composed of biochar was performed by experimental analysis and determination of optimum conditions of best performing synthesis methods using response surface methodology, biosorbent characterization, and possible mechanism of adsorption, which could potentially complement the removal of heavy metals from wastewater.