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.
Keywords: Aluminum; biosorption; cell wall; drinking water; rice straw.
This article provides a new interdisciplinary horizon at the border of plant biochemistry, agriculture, water treatment industry, and environmental protection. This study covers different aspects including biosorption, cell wall network as well as the usefulness of agricultural by-products in biosorption of Al-polluted drinking water. Findings of the present study revealed that rice straw cell wall polysaccharides have specific Al3+ binding sites, therefore can be effectively used in water treatment and reduce Al3+ content below the standard permissible limit of WHO (0.2 mg/L). This can be a foundation for future research to evaluate agricultural wastes management in the industry of water as natural biosorbent. This method also effectively converts RS from an unwanted agricultural waste to high-value products.