Phosphorous modified cocopeat biochar as a low cost, efficient and stable adsorbent for the removal of Cu(II) and Ni(II) from aqueous and real systems

Biochar is widely acknowledged as an environmentally efficient adsorbent for removing heavy metals from wastewater. However, its practical application is often limited by insufficient adsorption capacity. This limitation primarily arises from low surface area, suboptimal selection and utilization of chemical activating agents, and inadequate development of surface functional groups, leading to reduced stability. To address these challenges, the present study focuses on the synthesis and application of phosphoric acid-activated non-edible coco peat biochar (PMCB) for the efficient and stable removal of Cu²⁺ and Ni²⁺ from both aqueous solutions and real wastewater systems. Thus, this study focuses on the synthesis and application of phosphoric acid-impregnated non edible coco peat biochar (PMCB) for efficient and stable removal of Cu²⁺ and Ni²⁺ from both aqueous and real systems. The PMCB was prepared at combined optimal conditions (Pyrolysis temperature and H₃PO₄ impregnation ratio), which improved its physicochemical properties compared to that of pristine biochar. The PMCB exhibited superior adsorption capacities of 566.6 mg/g and 551.7 mg/g for Cu²⁺ and Ni²⁺ in batch tests and 794.5 mg/g and 691.4 mg/g in column studies. The adsorption data by PMCB were well fitted by the Langmuir isothermal and pseudo-second-order kinetic models, indicating monolayer chemical adsorption controlled the adsorption process. Characterisation using XPS and FTIR confirmed the presence of -PO₃ and -PO₄ functional groups in the modified biochar. These functional groups enhance metal adsorption through precipitation, physicochemical adsorption, surface complexation, ion exchange, and electrostatic interactions. PMCB demonstrated 99% removal efficiency for metals and pollutants in single-component and real-world systems. Stability tests showed PMCB's reusability for up to 20 cycles with a 96.0% desorption rate. Additionally, the spent biochar proved effective as a bio-fertilizer. Cost analysis confirmed PMCB to be economically viable at 1.56 USD/kg (130.7 INR/kg), making it a cost-effective, sustainable, and low-energy solution for industrial heavy metal removal and wastewater treatment.