From Waste to Resource: Assessing the Biosorption Efficiency of Citric Acid-Modified Activated Carbon from Corn (Zea Mays) Husks in Aqueous Copper (II) Ion Solutions

The global focus on cost-effective and sustainable adsorbents, specifically activated carbon from corn husk wastes, addresses environmental waste disposal issues. This economical solution efficiently removes heavy metal ions and promotes the use of agricultural biomass residue in wastewater treatment. In this study, unmodified and modified activated carbon produced from corn husk waste was investigated for the removal of Cu (II) ions in an aqueous solution. The activated carbon was modified with citric acid, resulting in citric acid corn husk activated carbon (CA-CHAC). Several batch adsorption experiments were carried out for both adsorbents to examine the influences of various factors, including pH, adsorbent dose, and contact time. Additionally, the adsorption system was fitted to isotherm and kinetic adsorption models to characterize its adsorption behavior. Results from adsorption studies showed that both the unmodified (CHAC) and citric acid-modified activated carbon (CA-CHAC) adsorbents achieve their optimum adsorption for Cu(II) at pH=7, with a dosage of 5 mg, and contact times of 45 minutes for CHAC and 30 minutes for CA-CHAC. The outcomes additionally demonstrated that the fundamental mechanism of both adsorbents is most effectively described by both the Langmuir isotherm model and the pseudo-second-order model, signifying that the adsorption system adheres to chemisorption. Maximum removal of Cu (II) ions using CHAC and CA-CHAC was obtained with 69.52% and 82.22% average removal, respectively. Additionally, the maximum adsorption capacities recorded were 77.58 mg/g for CHAC and 88.10 mg/g for CA-CHAC. The findings of this study indicate that corn husk-activated carbon modified with citric acid (CA-CHAC) has the potential to effectively adsorb Cu (II) ions.