Enhanced lanthanum-impregnated activated carbon derived from coffee grounds

This study introduces an innovative approach to utilizing spent coffee grounds (SCG) as a precursor for activated carbon, integrating alkali activation with lanthanum impregnation to enhance arsenic adsorption. Unlike previous studies focusing on simple activation, this work explores how metal oxide modification enhances selective adsorption performance. Based on thermogravimetric analysis, the optimal carbonization condition was determined to be 500°C for 2 hours, and this condition was consistently applied across all activation and impregnation procedures. Chemical activation with KOH at a mass ratio of 2.0 resulted in a favorable balance between carbon yield and micropore development, while NaOH activation at a 3.0 ratio promoted mesopore formation but reduced overall yield. Maximum iodine adsorption capacity reached 1200 mg/g under the optimal KOH activation condition. Although lanthanum hydroxide (La(OH)₃) impregnation slightly decreased iodine uptake, it significantly improved the removal of arsenic (As(V)), achieving an adsorption capacity of 60 mg/g at 20 % La(OH)₃ loading. Adsorption isotherm analysis demonstrated that arsenic adsorption followed the Langmuir model, indicating monolayer adsorption behavior with a high correlation coefficient (R² = 0.9988).