Adsorption and mechanism of nitrate from groundwater onto Si-Al porous clay mineral material as ceramic waste: characterization, kinetics, and adsorption isotherms

A Si-Al porous clay mineral material W (PCMW) as raw material for ceramic was prepared from two kinds of natural clay minerals. The waste of PCMW could be used as an adsorbent to remove nitrate (NO3-N) from groundwater. The characteristics of PCMW were determined by surface area, pore volume, scanning electron microscopy, X-ray fluorescence, powder X-ray diffraction, pH((zpc)), Fourier transform infrared spectroscopy, and zeta potential analyses. The optimum values of the effective parameters, such as the contact time (96-120 h), pH (<6.0), initial concentrations of NO3-N (25-40 mg/L), PCMW dosage (0.5-2 g), particle size of PCMW (1-3 mm), and temperature (288-303 K), were determined. The pseudo-first-order kinetic model and the Langmuir isotherm effectively described the adsorption process; the maximum adsorption capacity of PCMW as calculated from this model was 5.14-5.30 mg/g. Intraparticle diffusion and liquid film diffusion could affect the adsorption process. Kinetic models, isotherm models, and thermodynamic calculations demonstrated that the adsorption of NO3-N onto PCMW was a kinetically controlled, spontaneous, and endothermic monolayer physical process. The results of this study suggest that PCMW is suitable as a recyclable adsorbent material for the adsorption of NO3-N from groundwater.