贝壳粉对镉吸附特性的影响研究
发布时间:2018-02-13 12:19
本文关键词: 贝壳粉 镉污染 吸附 赋存形态 出处:《沈阳农业大学》2017年硕士论文 论文类型:学位论文
【摘要】:目前,重金属污染受到国内外的广泛关注。镉(Cd)作为典型的重金属污染物,具有较强的生物毒性。向镉污染水体和土壤中投加吸附材料是修复镉污染的有效措施之一。贝壳是水产品的副产物,具有资源丰富、成本低廉和无污染等特征。本文通过吸附试验及恒温培养试验,就扇贝以及蛏子壳粉对水体中镉的吸附特征与污染土壤镉存在形态的影响进行了研究。主要研究结论如下:供试扇贝及蛏子壳粉对水体中Cd2+均具有较强的吸附能力。随着贝壳粉用量的增加,供试贝壳粉对水体中Cd2+的吸附量先快速降低后达到平稳;随着Cd2+溶液初始pH值(1~6)的升高,吸附量逐渐增大;随着Cd2+溶液初始浓度的增加,吸附量逐渐增大;在吸附开始0~2h内吸附量快速增加,在吸附后期2~72h逐渐趋于不变。对于400℃扇贝壳粉(400ss)、天然扇贝壳粉(ss)和400℃蛏子壳粉(400rcs)来说,Freundlich等温吸附模型能够更好地拟合吸附过程,R2在0.944~0.993之间,对于天然蛏子壳粉(rcs)来说,Langmuir和Freundlich两种模型均能较好地拟合吸附过程,R2均大于0.966;在贝壳粉对Cd2+的吸附过程中,温度升高能够促进吸附,表明吸附为吸热的过程;通过对比三种吸附动力学模型(准一级、准二级以及颗粒内扩散模型),发现400ss、ss、400rcs和rcs对Cd2+的吸附动力学过程与准二级动力学最为相符,R2达到0.999。对于不同来源贝壳粉而言,rcs的吸附效果远远高于400ss、ss和400rcs,qe 达到 485.32mg/g。添加400ss、ss、400rcs和rcs对土壤pH值升高均具有一定程度的贡献,培养50d后,ss1~ss5、rcs1~rcs5、400ss1~400ss5 和 400rcs1~400rcs5(贝壳粉施加比例为风干土质量的1%~5%)分别比CK高0.99~1.09、1.03~1.12、1.00~1.05和1.03~1.10个单位,所有处理与CK相比均存在显著差异(p0.05),同时不同添加比例间均存在显著差异(p0.05);在0~50d的培养期间,添加贝壳粉均能够使土壤有效态镉的含量下降,且添加比例越大降低效果越明显,在培养50d后,ss5、rcs5、400ss5和400rcs5处理的土壤有效态镉含量分别为5.46、5.37、5.51和5.51mg/kg。随着培养天数延长或者贝壳粉添加比例越大,可交换态镉向碳酸盐结合态镉、铁锰氧化物结合态镉、有机物结合态镉和残渣态镉转化的程度越大。不同来源贝壳粉对土壤镉赋存形态的影响不同,添加rcs对镉污染土壤的修复效果优于400rcs,ss优于400ss,表明在修复镉污染土壤时焙烧两种天然贝壳粉至400℃无必要;在培养50d后,所有处理中rcs5对镉污染土壤的修复效果最佳,与CK相比,可交换态镉含量降低了 28.51%,碳酸盐结合态镉、铁锰氧化物结合态镉、有机物结合态镉以及残渣态镉含量依次升高了50.19%、16.08%、29.74%以及 32.68%。
[Abstract]:At present, heavy metal pollution has attracted wide attention both at home and abroad. Cadmium (CD) is a typical heavy metal pollutant. The addition of adsorbent materials to cadmium contaminated water and soil is one of the effective measures for remediation of cadmium pollution. Shells are by-products of aquatic products and rich in resources. The characteristics of low cost and no pollution. In this paper, adsorption test and constant temperature culture test are carried out. The effects of scallop and clam shell powder on the adsorption characteristics of cadmium in water and the forms of cadmium in contaminated soil were studied. The main conclusions are as follows: both scallop and clam shell powder have strong adsorption energy for Cd2 in water. With the increase of shell powder, With the increase of initial pH value of Cd2 solution, the adsorption capacity increased gradually, and the adsorption capacity increased with the increase of initial concentration of Cd2 solution, and the adsorption capacity increased with the increase of initial concentration of Cd2 solution. The adsorption capacity increased rapidly within 2 hours after the beginning of adsorption. For 400 鈩,
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