Spent Coffee Grounds as a Low-Cost Biosorbent for Arsenic Removal from Drinking Water: A Proof-of-Concept Study

Source abstract

Arsenic contamination of drinking water remains a major environmental and public health challenge worldwide, particularly in regions with limited access to advanced treatment technologies. This proof-of-concept study evaluated the feasibility of untreated spent coffee grounds (SCG) as a low-cost biosorbent for arsenic removal from drinking water and assessed the potential of alginate immobilization for future engineering applications. Batch adsorption experiments were performed using synthetic As(V) solutions containing 20 and 100 μg L⁻¹. Untreated SCG (1.0 g) was contacted with 100 mL of arsenic solution for 180 min. We quantified residual arsenic concentrations by inductively coupled plasma (ICP), and monitored pH changes before and after adsorption. We characterized surface morphology and elemental composition using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Untreated SCG achieved arsenic removal efficiencies greater than 98%, reducing initial concentrations of 20 and 100 μg L⁻¹ to 0.250 and 1.24 μg L⁻¹, respectively, both below the World Health Organization and United States Environmental Protection Agency drinking water guideline of 10 μg L⁻¹. Apparent adsorption capacities were 0.001975 and 0.009876 mg g⁻¹, while only minor pH variations were observed, indicating good chemical stability of the biosorbent. Alginate immobilization preserved removal efficiencies above 98%, supporting its potential for practical applications. SEM analysis showed that the characteristic porous morphology of SCG was maintained after adsorption, whereas EDS provided qualitative evidence of localized arsenic retention on the biosorbent surface. These findings demonstrate that untreated SCG constitutes a promising, sustainable, and inexpensive biosorbent for arsenic removal and provide a strong foundation for future optimization and scale-up studies aimed at decentralized drinking water treatment.