不同粒径污泥生物质炭对水体中Zn污染的吸附效应研究

为了探究3种不同粒径的污泥生物质炭(S1:大粒径 0.165 mm;S2:中粒径为0.025～0.165 mm;S3:小粒径0.025 mm)对Zn的吸附效率和固化稳定的机理,以此为污泥生物质炭在水污染控制方面的应用提供科学依据.利用实验室模拟法,研究不同反应时间、溶液初始pH和重金属浓度对生物炭吸附效果的影响,并运用四步萃取法分析生物炭上Zn的吸附形态.结果表明:①生物炭在4 h左右达到吸附平衡,吸附率呈先增加后平缓的趋势,最终吸附量S1S2S3;②溶液初始浓度为0～2 mmol·L~(-1)时Zn~(2+)的吸附量呈线性增长趋势,但随溶液浓度超过2 mmol·L~(-1)时吸附量开始趋于饱和;③3种不同粒径生物炭的水溶性组分Zn分别占总萃取量的1.70%、5.02%和7.47%,可交换态组分分别占25.27%、32.35%和27.29%,酸溶性组分分别占35.06%、38.63%和27.90%,非生物利用组分分别占37.97%、24.00%和37.34%.④污泥生物质炭的动力学吸附特征更符合准二级动力学吸附模型,单位质量的污泥生物质炭粒径越小吸附量越大;⑤污泥生物质炭的等温吸附特征更符合Langmuir模型,小粒径的生物质炭最大吸附量最优;⑥在酸性条件下随着pH的上升污泥生物质炭的吸附率在逐渐增加,碱性条件下吸附率的增加可能是形成锌的络合物沉淀导致的;⑦Zn的吸附形态以酸溶性和非生物利用态为主,水溶性占比较小.污泥生物质炭对Zn的吸附以化学吸附为主,S1吸附的Zn酸溶性组分和非生物利用组分占比最大,吸附效果较为稳定.

Adsorption effects of sludge biochar of different particle sizes on Zn contamination in water

We investigated the effects of biochar of three particle sizes derived from sludge (S1:large particle size,>0.165 mm; S2:medium particle size, 0.025~0.165 mm; S3:small particle size, <0.025 mm. Here, "S" represents the particle size.) on the adsorption efficiency and the mechanism of solidification stability of Zn and provide a scientific basis for the application of sludge biochar in water pollution control. A laboratory simulation was performed to investigate the effects of reaction time, initial pH, and heavy metal concentration on the adsorption efficiency of biochar, and a four-step extraction method was used to analyze the adsorption form of Zn. The biochar attained adsorption equilibrium after~4 h. The adsorption rate initially increased and then stabilized. The final adsorption amount was in the order of S1 > S2 > S3. The amount of absorbed Zn²⁺ increased linearly for an initial solution concentration of 0~2 mmol·L^-1 However, the absorption began to exhibit saturation when the concentration exceeded 2 mmol·L^-1. In the three biochar samples of different particle sizes, the water-soluble components of Zn constituted 1.70%, 5.02%, and 7.47%, the exchangeable form components constituted 25.27%, 32.35% and 27.29%, the acid-soluble components constituted 35.06%, 38.63%, and 27.90% and the non-bioavailable components constituted 37.97%, 24.00%, and 37.34% of the total extraction amounts. The kinetic adsorption characteristics of sludge biochar are best described by the quasi-second-order kinetic adsorption model. As the particle size of the sludge biochar per unit mass decreases, the adsorption capacity increases. The isothermal adsorption characteristics of sludge biochar are best described by the Langmuir model, and the maximum adsorption capacity of biochar with a small particle size is optimal. Under acidic conditions, the adsorption rate of the sludge biochar increases with increasing pH. Under alkaline conditions, the increased adsorption rate may be caused by the precipitation of Zn-forming complexes. The adsorption forms of Zn are primarily acid-soluble and non-bioavailable forms together with a small proportion of the water-soluble form. Zn adsorption by sludge biochar is primarily chemical. The acid-soluble and non-bioavailable components in Zn constitute the largest proportion of Zn adsorbed by S1 particles, and the Zn adsorption effects are relatively stable.