发酵稻壳对亚铁离子和硫离子的吸附-解吸附特性

为了解发酵稻壳对Fe2+和S2-离子的固定潜力,采用静态批式法研究了发酵稻壳对Fe2+和S2-离子的吸附行为,探讨了反应时间、溶液中Fe2+和S2-浓度、溶液p H、吸附反应环境温度及溶液离子强度对发酵稻壳吸附Fe2+和S2-特性的影响,并进一步通过解吸附试验了解发酵稻壳吸附态Fe2+和S2-的稳定性.结果表明,发酵稻壳吸附Fe2+(r=0.912 1)和S2-(r=0.901 1)的动力学过程均符合Elovich动力学模型,且Fe2+(R2=0.965 1)和S2-(R2=0.936 6)的等温吸附特征可较好地用Freundlich等温吸附模型描述.发酵稻壳对Fe2+和S2-的吸附为非优惠型吸附,其中对Fe2+的吸附为非自发反应,对S2-的吸附为自发反应.发酵稻壳对Fe2+和S2-的吸附过程是一吸热过程,升温有利于吸附作用的进行,发酵稻壳对Fe2+的吸附主要为配位吸附,而对S2-的吸附主要为阴离子交换吸附.一定p H范围内(1.50~11.50)发酵稻壳吸附Fe2+和S2-具有较强的适应性.同时随着离子强度的增加发酵稻壳对Fe2+的吸附量有所增加,而对S2-的吸附量略有减少,进一步证明发酵稻壳对Fe2+的吸附以内层配位为主,对S2-的吸附以外层络合为主.此外,不同p H条件及离子强度下发酵稻壳吸附的Fe2+和S2-解吸率很低,解吸率均小于10.00%.上述结果说明,发酵稻壳对Fe2+和S2-具有较好的吸附能力和环境适应性,吸附态Fe2+和S2-稳定性好,不易再释放.

Adsorption-desorption Characteristics of Fermented Rice Husk for Ferrous and Sulfur Ions

To understand the potential of rice husk to fix Fe²⁺ and S^2- ions, the sorption of Fe²⁺ and S^2- by fermented rice husk was studied by using batch incubation experiments in the present study.The effects of adsorption time, Fe²⁺ and S^2- concentration, pH, the temperature and ionic strength in adsorption reaction solution on the sorption were investigated.Therefore, the stability of Fe²⁺ and S^2- adsorbed by fermented rice husk was further validated by desorption experiments performed under similar conditions as adsorption.The results showed that, the adsorption kinetics of Fe²⁺ (r=0.9121) and S^2- (r=0.9011) by fermented rice husk fits the Elovich kinetics equation, and Freundlich isotherm model could simulate the isotherm adsorption processes of Fe²⁺ (R²=0.9651) and S^2- (R²=0.9366) on fermented rice husk was better than other models.The adsorption processes on fermented rice husk were non-preferential adsorption for Fe²⁺ and S², while the adsorption process of Fe²⁺ on fermented rice husk was spontaneous reaction and the adsorption process of S^2- was non-spontaneous reaction.The adsorption processes of Fe²⁺ and S^2- on fermented rice husk were endothermic process since high temperature could benefit to the adsorption.The adsorption mechanism of Fe²⁺ on fermented rice husk was mainly controlled by coordination adsorption, the adsorption mechanism of S^2- on fermented rice husk was mainly controlled by ligand exchange adsorption.The adsorption processes of Fe²⁺ and S^2- on fermented rice husk showed greater pH adaptability which ranged from 1.50 to 11.50.With the increasing of ionic strength, the amount of adsorbed Fe²⁺ on fermented rice husk wasincreased in some extent, the amount of adsorbed S^2- on fermented rice husk was slightly decreased, which further proved the adsorption of Fe²⁺ was major in inner sphere complexation and the adsorption of S^2- was major in outer complexation.The desorption rates of Fe²⁺ and S^2- which was adsorbed by fermented rice husk were lower in different pH or ionic strength conditions, the desorption rates were all below 10 percentage which proved that the adsorption stabilities of Fe²⁺ and S^2- on fermented rice husk were superior.The above results indicated that, the adsorption abilities to Fe²⁺ and S^2- on fermented rice husk were better and had greater environmental adaptability.The Fe²⁺ and S^2- adsorbed by fermented rice husk showed higher stability, and were not easy to release again.