Effective biosorption of Al ions from drinking water by lignocellulosic biomass rice straw.

High concentration of aluminum (Al) in drinking water is a major intake source of it and can result in serious diseases. Rice straw (RS) as lignocellulosic biomasses has great potential to peak up metal ions from aqueous environment, however, feasibility of Al³⁺ removal by RS has not been investigated yet. The present study aimed to evaluate the capacity of RS as a novel biosorbent for Al³⁺ from drinking water. Biosorption characteristics of RS were surveyed through several biological and physiochemical techniques. Additionally, isotherm, kinetic and thermodynamic studies were evaluated using various common models. BET profiles revealed the presence of textural mesoporosity on heterogeneous surface, which leading to improve the biosorption capacity. SEM-EDS analysis confirmed the morphological changes as irregularly particles of Al³⁺ on external surface via physical mechanism. The results of bioassays and FTIR analysis showed carboxylic and hydroxyl groups in lignin and pectin as the main Al³⁺ binding site. The batch experimental results showed the maximum biosorption capacity of 283.09 mg/g and removal efficiency of 94.86% for Al³⁺ at biosorbent dosage of 0.05 g/100 mL, contact time of 50 min, pH 7.5, and temperature of 30 °C. The Freundlich model has the best match and suggests the biosorption process as a multi-layer. According to the results of free activation energy, biosorption process was also physical. As thermodynamic result, the biosorption behavior was found spontaneous and endothermic. Consequently, results showed RS as an economical biosorbent for reducing Al³⁺ of drinking water. Meanwhile, it can be considered as one of the most appropriate methods for management of rice paddies waste.