Investigation of nitrate removal from drinking water by adsorption using red clay modified with sulfuric acid

Elevated nitrate levels (NO₃⁻) in water resources pose significant risks to public health and the environment. This study aims to develop a cost-effective adsorption method for removing NO₃⁻ from drinking water using red clay modified with sulfuric acid (H₂SO₄). The modified adsorbent was characterized through Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analyses to confirm structural changes. The influence of key operational parameters, including pH, adsorbent dosage, contact time, initial nitrate concentration, temperature, and reuse potential, was systematically investigated. Nitrate concentrations were measured using a spectrophotometer at 220 nm, and data analysis was conducted using Design-Expert® and Microsoft Excel. FTIR results confirmed the successful sulfonation of functional groups on the clay surface, enhancing its adsorption capacity. The optimized conditions achieved a maximum nitrate removal efficiency of 81% at pH 4, with 1 g of adsorbent, a 60 min contact time, an initial nitrate concentration of 100 mg/L, and a temperature of 20 °C. Under the same conditions, nitrate removal efficiency in synthetic solutions reached 90%. These findings demonstrate that H₂SO₄-modified red clay is a promising and sustainable adsorbent for nitrate removal from drinking water, with significant potential for practical applications in water treatment systems.