CA/COSBC复合凝胶微球的制备及其对Pb(II)的吸附性能

Preparation of composite gel ball CA/COCSBC and its adsorption performance on Pb(II)

摘要:

本实验以废弃油茶果壳(Camellia oleifera shell,COS)为原料制备生物炭(COSBC),并将其均匀分散到海藻酸钠凝胶溶液,形成混合凝胶溶液,采用球滴法,将混合凝胶溶液逐滴滴入CaC12溶液中,使海藻酸钠发生交联,制备复合海藻酸钙(Calcium alginate,CA)凝胶微球(CA/COSBC)。实验结果表明,制备 CA/COSBC凝胶微球的最佳工艺条件为:海藻酸钠(2%)与COSBC质量比为4:1,2% CaCl2作凝固浴,固化时间为60 min。利用扫描电子显微镜(SEM)和傅里叶变换红外光谱(FTIR)等技术对CA/COSBC微球的形貌结构进行表征。采用该CA/COSBC微球作吸附材料,结合原子吸收光谱法研究其对水体中重金属离子Pb(II)的吸附去除效果。考察了溶液 pH与温度、CA/COSBC投加量、Pb(II)初始浓度、吸附时间等因素对水中Pb(II)去除效果的影响,探究了CA/COSBC凝胶球对Pb(II)的热力学和动力学行为。结果表明,CA/COSBC微球在pH值为5、投加量0.77 g/L时,在250 mg/L Pb(II)溶液中吸附4 h, 废水中Pb(II)的去除率高达72.81%,CA/COSBC对Pb(II)的吸附量为236.4 mg/g。吸附过程能够自发进行且符合Freundlich热力学模型和准二级动力学模型,说明多分子层的化学吸附占主导作用。颗粒内扩散不是控制吸附过程的唯一因素,表面吸附和边界层扩散也会造成影响。

Abstract:

The biological carbon (COSBC) was prepared with camellia oleifera shell (COS) as raw material.and it was uniformly dispersed into sodium alginate gel solution to form a mixed gel solution. The composite calcium alginate gel microspheres (CA/COSBC) were prepared with ball drop method through the mixed gel solution as matrix precursor dripping into CaCl2 solution for cross-linking action between Ca2+ and sodium alginate. The results indicated that the optimum conditions for the preparation of CA/COSBC microspheres were as follows: the mass ratio of sodium alginate (2%) to COSBC was 4 : 1, 2 % CaCl2 as coagulation bath, and the curing time was 60 min. The morphological structure of CA/COSBC was characterized by SEM and FTIR spectrum. The effects of CA/COSBC dosage, solution pH and temperature, initial concentration of Pb(II), and adsorption time on the adsorption effect of Pb(II) in wastewater were investigated in detail, and the thermodynamic and kinetic behavior of CA/COSBC adsorption for Pb(II) were explored. The results showed that the removal rate of Pb (II) in wastewater was as high as 72.81 % under the conditions of room temperature, pH 5 and 250 mg/L Pb (II) solution, adsorbent dosage of 0.77 g/L and contact time 4 h. The adsorption capacity of CA/COSBC for Pb (II) was 236.4 mg/g. The adsorption process was spontaneous and conformed to the Freundlich thermodynamic model and the pseudo-second-order kinetic model. The results showed that the chemical adsorption of the multi-molecular layer played a dominant role. In addition, intraparticle diffusion is not the only factor controlling the adsorption process, and surface adsorption and boundary layer diffusion can also affect it.