羧基稻草阳离子吸附剂的制备及其去除水溶液中亚甲蓝的研究

为促进工业废水处理并降低废水处理费用,研究了柠檬酸热化学酯化法改性稻草制备可生物降解阳离子吸附剂的方法.实验比较了天然和改性稻草去除溶液中阳离子染料(亚甲蓝)的能力,研究了不同实验参数(pH值、吸附剂量、染料浓度、离子强度、吸附时间)对亚甲蓝吸附效果的影响在pH为2～10范围内,天然稻草去除亚甲蓝的能力随pH值的增加而增加,而改性稻草在pH≥3时对染料的去除率达到最大.改性稻草用量大于1.5g·L-1时几乎能完全去除浓度为250mg·L-1亚甲蓝溶液中的染料.改性稻草用量为2.0g·L-1对浓度为50～450mg·L-1的亚甲蓝溶液去除率保持在98%以上.增加溶液的离子强度会导致亚甲蓝去除率降低.染料吸附等温线符合Langmuir模式.吸附过程符合准一级反应动力学方程.酯化改性使染料的吸附剂粒子内扩散速率常数(kid)大大增加.研究结果表明,改性稻草是良好的亚甲蓝吸附剂.

Preparation and utilization of rice straw cationic sorbent bearing carboxyl groups for removal of methylene blue from aqueous solution

In order to enhance the treatment of industrial wastewater and reduce the cost of wastewater treatment, rice straw was esterified thermochemically with citric acid to produce potentially biodegradable cationic sorbent. The crude and modified rice straws were assessed for their cationic dye (methylene blue) removal capacity from aqueous solution. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, ion strength, and contact time etc.) were examined. The ratio of methylene blue (MB) adsorbed on crude rice straw increased as the initial pH was increased from pH 2 to pH 10. For modified rice straw (MRS), the MB removal ratio came up to the maximum value beyond pH 3. The 1.5 g·L^-1 or up of MRS could almost completely remove the dye from 250 mg·L^-1 of MB solution. The adsorbed ratio of MB kept above 98% over a range from 50 to 450 mg·L^-1 of MB concentration when 2.0 g·L^-1 of MRS was used. The increase of the ion strength of the solution induced decline of MB sorption. The isothermal data fitted the Langmuir model. The sorption processes followed the pseudo-first-order rate kinetics. The intraparticle diffusion rate constant (k_id) was greatly increased due to chemical modification. The results in this research confirmed that MRS was an excellent MB sorbent.