Enhancing the performance of natural clay for nitrate ions removal from groundwater and wastewater of the region of Taroudant (Souss-Massa Morocco): mechanism, optimization and evolution toxicity

This paper discusses the adsorption mechanism of nitrate ions using natural clay from an aqueous solution. The adsorbent’s heterogeneous structure with deep voids and significant porosity was also seen under the scanning electron microscopy (SEM). This structure is assumed to be essential for binding and collecting nitrate ions onto the adsorbent surface. Different functional groups have been identified to facilitate the adsorption of nitrate ions onto adsorbent. The Brunauer Emmett et Teller (BET) surface examination revealed that the natural raw clay (NRC) surface is around 6.44 m²/g. With a 98 % correlation coefficient, the Langmuir isotherm is the most appropriate model to explain the adsorption process. 241.18 mg/g was the maximum adsorption capacity for nitrate ions at 291 K. The pseudo second-order model represents a good explanation of adsorption kinetics. According to thermodynamic calculations, adsorption occurs spontaneously and exothermically on natural clay. The natural clay was recycled; the removal of nitrates was 42.08 % after the third cycle.The results of Taguchi experimental design (TED), analysis of variance (ANOVA), and response surface methodology (RSM) showed that initial concentration, contact time, and pH are the most significant factors influencing the efficiency of removal with a contribution of 76.96 %, 11.29 %, and 4.3 %, respectively. The maximum removal efficiency of nitrate ions in optimal operating conditions was 82.67 %. Which at the optimal conditions of 0.5 g/L, 360 min, 1000 mg/L, 18 °C, pH 4 for nitrate ions. The results confirm the effectiveness of natural clay in lentil seed germination and nitrate removal from water.