Method of producing magnetite-modified biochar for heavy metal removal

Abstract

The invention relates to a method of producing magnetite-modified biochar from Acacia (Albizia saman) seed pods for use as sorbent for heavy metal removal in aqueous solution. The method comprises washing, drying, crushing, carbonizing through slow pyrolysis at 400 °C for 2 hours, preparing magnetite, mixing biochar and magnetite with varying mass percentage of magnetite, adjusting the pH by dropwise addition of sodium hydroxide solution, filtering and recovering the modified biochar, followed by final rinsing and drying. The biochar produced through this method is iron enriched, with increased surface complexity and functionalization that enhanced its affinity toward copper ions. This invention distinguishes itself from existing sorbent materials by using a low-cost, locally abundant biomass from a considered invasive plant species, and a simple method to modify the biochar with magnetite. The magnetite-modified biochar exhibited improved sorption behavior relative to unmodified biochar. All modified biochar follow multilayer adsorption with adsorption capacities up to 28.01 mg g-1. All biochar samples followed a chemisorption-dominant mechanism with equilibrium adsorption capacity reaching 18.83 mg g-1. These findings demonstrate the potential of magnetite-modified biochar as an effective and sustainable adsorbent and alternative for heavy metal remediation, supporting its application in wastewater treatment and circular resource utilization.