Goat Horn Biochar as a Low-Cost Adsorbent for the Removal of Cadmium and Zinc ions in Aqueous Solution

Abstract

Given the high toxicity of most heavy metal ions in aquatic environments and the need for remediation using environmentally friendly methods, this study was conducted to produce biochar from goat horn. The removal efficiency of the synthesised biochar in the removal of cadmium (Cd²⁺) and zinc (Zn²)⁺ions from aqueous solutions was also investigated. The proximate analysis of the goat horn biochar was carried out, the moisture content, ash content and bulk density were 10.62%, 6.5% and 0.79g/cm³ respectively. FTIR characterization shows the function group of O-H, C=H, C-O, C=C and P-O. SEM analysis shows a distinct porosity and irregular surfaces with roughness. The batch adsorption experiment was also implemented to obtain information on the influence of pH, metal concentration and contact time on the removal efficiency of the biochar. The results of the study indicated that the optimal conditions for the removal of the metal ions was a pH of 7, 20mg/L.  The adsorption equilibrium was obtained after 60 and 90 minutes of contact for Cd²⁺ and Zn²⁺respectively.The adsorption data fitted the Langmuir isotherm with a correlation coefficient (R²> 0.94) and suggested a uniform distribution of bonding energy between the Cd²⁺ and Zn²⁺ on biochar. The maximum adsorption capacity was 38.84 mg/g for Cd²⁺ and 33.692 mg/g for Zn²⁺. The kinetic study enlisted the pseudo-second-order as the best-fitted model. The adsorption was proposed to be facilitated by the chemisorption mechanism.