Enhanced elimination of nitrate and nitrite ions from ground and surface wastewater using chitosan sphere-modified Mg-Al layered double hydroxide composite

Abstract

Excess nitrate and nitrite ions are harmful contaminants for groundwater and surface waters, disrupting biological balance. In this study, Mg-Al layered double hydroxide modified by chitosan spheres (CS@LDH) is used for ion adsorption and studied composites’ structural and morphological features using XRD, HR-TEM, FE-SEM, and XPS. The CS@LDH composite’s positive zeta potential (38.42 mV) and larger surface area (84.62 m/g) aid absorb negatively charged ions. With optimised 3 mg CS@LDH in 10 mL (30 mg/L) of nitrate ion concentration at optimum pH 4, the maximum adsorption capacity was 98.7 % in 90 min at 298 K. The Langmuir isotherm study indicated that nitrate ions had a maximum adsorption capacity of 2026.7 mg/g and nitrite ions 1086.8 mg/g. SEM pictures validate the heterogeneous adsorption features of CS@LDH composites. According to the pseudo-first-order kinetics model (k = 6.4 × 10 min, R 1), physisorption is the rate-limiting phase. Elovich kinetic studies show active adsorption without product desorption. Experimental and characterization investigations confirmed the CS@LDH nitrate adsorption mechanism. CS@LDH removed nitrates from real-life wastewater, and within three hours, NO was below drinking water safety levels. The combination of naturally occurring biopolymers and double-layered hydroxides in this research might remove numerous harmful pollutants from wastewater.