发酵稻壳对亚铁离子和硫离子的吸附-解吸附特性

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

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.

To understand the potential of rice husk to fix Fe2 +and S2-ions,the sorption of Fe2 +and S2-by fermented rice husk was studied by using batch incubation experiments in the present study. The effects of adsorption time,Fe2 +and S2-concentration,p H,the temperature and ionic strength in adsorption reaction solution on the sorption were investigated. Therefore,the stability of Fe2 +and S2-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. 912 1) and S2-( r = 0. 901 1) by fermented rice husk fits the Elovich kinetics equation,and Freundlich isotherm model could simulate the isotherm adsorption processes of Fe2 +( R2= 0. 965 1) and S2-( R2= 0. 936 6) on fermented rice husk was better than other models. The adsorption processes on fermented rice husk were nonpreferential adsorption for Fe2 +and S2,while the adsorption process of Fe2 +on fermented rice husk was spontaneous reaction and the adsorption process of S2-was non-spontaneous reaction. The adsorption processes of Fe2 +and S2-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 S2-on fermented rice husk was mainly controlled by ligand exchange adsorption. The adsorption processes of Fe2 +and S2-on fermented rice husk showed greater p H 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 S2-on fermented rice husk was slightly decreased,which further proved the adsorption of Fe2 +was major in inner sphere complexation and the adsorption of S2-was major in outer complexation. The desorption rates of Fe2 +and S2-which was adsorbed by fermented rice husk were lower in different p H or ionic strength conditions,the desorption rates were all below 10 percentage which proved that the adsorption stabilities of Fe2 +and S2-on fermented rice husk were superior. The above results indicated that,the adsorption abilities to Fe2 +and S2-on fermented rice husk were better and had greater environmentaladaptability. The Fe2 +and S2-adsorbed by fermented rice husk showed higher stability,and were not easy to release again.