Adsorption potential of native, acid, and ionic liquid-treated biochar derived from Prosopis juliflora towards chromium removal from simulated solutions: isotherm, kinetics, and characterization

Water resource contamination by heavy metal-ion-containing industrial effluents is a major problem. This work highlights the potential of Prosopis juliflora biochar, an invasive weed species, as an ecologically acceptable and practical adsorbent for the removal of Cr(VI) from aqueous media. To create modified biochars, orthophosphoric acid (APJB) and ionic liquid, 1-butyl-3-methylimidazolium chloride (ILPJB) were used for chemical modification of Prosopis juliflora biochar (PJB). The Cr(VI) adsorption process parameters were optimized for all three biochars at pH 2.0 during batch adsorption investigations. The dosage needed by ILPJB was 0.18 g, which is less than PJB and APJB. The experimental data fits the Freundlich model well, according to the modeling of the data using several isotherm models. The Freundlich model, which assumed the development of an adsorbate multilayer on the surface of the adsorbents, provided a satisfactory explanation for the Cr(VI) adsorption pattern. ILPJB (36.63 mg/g) had the highest Cr(VI) adsorption capacity (q(m)), followed by APJB (21.10 mg/g), and PJB (19.27 mg/g). The examination of experimental data fitting on various kinetic models was performed for Cr(VI) adsorption onto PJB, APJB, and ILPJB. Among that, the pseudo-second-order kinetic model best suited the data. The thermodynamic study verified the spontaneous nature and endothermic adsorption of Cr(VI). Based on this, it was determined that biochar treated with ionic liquid is a potential adsorbent for chromium adsorption from aqueous solutions.