Reducing Nitrate from Water Using Lanthanum-Modified Adsorbent: Optimization, Thermodynamics, Kinetics, Isotherms

Lanthanum-Modified commercial Activated Carbon (LMAC) adsorbent was synthesized, characterized, and then applied for reducing nitrate from aqueous solutions under various conditions. The extent of nitrate removal depended on four factors: temperature, the aqueous solution pH, initial nitrate concentration, and contact time. The Taguchi approach was used as the method of design for the experiments. Under optimal conditions ( T= 300°C, pH=3, C0=10 ppm, and t= 210 min), the removal percentages and capacity of nitrate adsorption were found to be 71.31%, and 1.43 for activated carbon (AC) and 93.31%, and 1.87 LMAC, respectively. Thermodynamic parameters, including enthalpy, Gibbs free energy, and entropy, indicated the spontaneous and exothermic nature of the adsorption process. Various isotherms and first and second-order kinetic models were applied to investigate the adsorption process. The pseudo-second-order kinetic model and Langmuir isotherm could well describe the adsorption process.