Adsorption of Phosphate from Agricultural Drainage Water Using Lanthanum-Modified Layered Double Hydroxide

Abstract

Excessive phosphate discharge from agricultural drainage water is a major contributor to eutrophication and deterioration of aquatic ecosystems, creating an urgent need for efficient nutrient removal technologies. This study investigates the adsorption of phosphate from agricultural drainage water using lanthanum-modified layered double hydroxide (La-LDH) as an advanced adsorbent material with enhanced phosphate affinity and selectivity. The research focuses on evaluating adsorption performance, reaction mechanisms, and operational factors affecting phosphate removal efficiency under varying environmental conditions. Experimental analyses were conducted to examine the influence of pH, adsorbent dosage, contact time, initial phosphate concentration, temperature, and competing ions on adsorption behavior. Results demonstrated that lanthanum modification significantly improved the phosphate adsorption capacity of layered double hydroxide through strong electrostatic interactions and surface complexation mechanisms. The adsorbent exhibited rapid adsorption kinetics, high selectivity toward phosphate ions, and stable performance over a wide range of operating conditions. Equilibrium studies confirmed favorable adsorption characteristics consistent with monolayer adsorption behavior, while kinetic modeling indicated that chemisorption played a dominant role in the phosphate removal process. The treated water showed substantial reduction in phosphate concentration, indicating the effectiveness of the developed adsorbent for nutrient control applications. Furthermore, regeneration studies revealed good reusability and structural stability of the adsorbent after multiple adsorption–desorption cycles. Compared with conventional nutrient removal methods, the proposed approach offers improved adsorption efficiency, lower sludge generation, and greater environmental sustainability. The findings highlight the potential of lanthanum-modified layered double hydroxide as an effective material for phosphate remediation and water quality management in agricultural and environmental engineering applications.