钛/钙氢氧化物的制备及其对As(Ⅲ)和As(V)的吸附研究

On the preparation of Ti / Ca hydroxide and its adsorption characteristics on As(Ⅲ) and As(V)

采用共沉淀法制备了钛/钙氢氧化物新型吸附剂,并对其吸附除As的性能进行了初步研究。考察了不同制备方法、Ti/Ca比例、p H值、Ca2+、磷酸根离子对As(Ⅲ)和As(V)去除率的影响,研究了所制备吸附剂对As(Ⅲ)和As(V)的吸附热力学特性,并对其吸附机理进行了探讨。结果表明:所制备吸附剂对As(Ⅲ)具有优异的选择性;吸附去除率试验中,吸附剂投加量0.2 g/L、As质量浓度1 mg/L、20℃、吸附3 h条件下,TC-45/5吸附剂对As(Ⅲ)的去除率达到97.3%,对As(V)的去除率为78.2%;酸性条件和Ca2+可显著提高As(V)去除率,但对As(Ⅲ)吸附去除的影响不大;磷酸根离子由于竞争吸附而导致As去除率下降,且对去除As(V)的抑制作用更强烈;30℃时,As(Ⅲ)与As(V)的Langmuir饱和吸附量分别为30.21 mg/g和16.61 mg/g。研究表明,钛/钙氢氧化物对As(Ⅲ)去除效果良好。

This paper is aimed to introduce its study results on the influential factors on the removing efficiency of As（ Ⅲ） and As（ V） from the drinking water by synthetic Ti / Ca hydroxide. It is just for this purpose that has pushed us to synthesize the binary mixed hydroxide of titanium and calcium（ Ti / Ca hydroxide） via a low-cost coprecipitation process. At the same time,we have done a series of experiments to explore the effects of the preparation method,Ti / Ca ratio,the solution ＇s p H value,Ca2 ＋and the phosphate anion. Meanwhile,we have also traced the adsorption thermodynamics properties of As（ Ⅲ） and As（ V） by materials with a discussion of the adsorption mechanism. The results of all the above experiments show that As（ Ⅲ） removing rate can be promoted to 97. 3% with the adsorbent dosage of 0. 2 g / L at the temperature of 20 ℃ and As（ Ⅲ） mass concentration of 1 mg / L at an initial p H value in 3 hours of adsorption,whereas As（ V）removal rate of the contrast experiment only remains 78. 2%. It proves that Ti / Ca hydroxide enjoys a kind of superior adsorption tendency on As（ Ⅲ）. Besides,the adsorbent could be successfully chosen to remove As（ Ⅲ） and As（ V） in the natural p H range. The conditions of p H = 5-9 and Ca2 ＋don＇t show any obvious effect on As（ Ⅲ） adsorption,but the presence of phosphate anion in the solution displays somewhat inhibition of As（ Ⅲ） adsorption. Acidic condition and Ca2 ＋can significantly enhance the removal efficiency of As（ V） whereas the phosphate anion shows serious negative results. The experimental data for As（ Ⅲ） adsorption can be fairly well（ R2= 0. 986） depicted by Langmuir isotherm（ R2= 0. 9958）,whereas Freundlich isotherm can well be used to describe the experimental data for As（ V） adsorption perfectly（ R2= 0. 9856）. The maximum adsorption capacity values of As（ Ⅲ） and As（ V） could reach 30. 21 mg / g and 16. 61 mg / g calculated by Langmuir isotherm at 30 ℃,respectively.The parameters of D-R isotherm gained through calculation can help to show that the adsorption of As（ Ⅲ） on Ti / Ca hydroxide tends to be of a physical adsorption process. And,accordingly,the adsorbent developed in this paper proves to be effective and well-fit for treating the arsenic polluted groundwater.