炭质吸附剂孔径分布与焦化废水有机组分分离的相关性

Correlation between pore-size distribution of carbonaceous sorbent and the separation of organic components in coking wastewater

选取4种孔隙结构不同的炭质吸附剂木质(A_1)、椰壳(A_2)、煤质(A_3)和焦炭(H)吸附焦化废水中的总有机碳(TOC)成分,考察吸附性能、分子量大小等因素对吸附效果的影响,同时利用傅里叶红外光谱、比表面积及介孔/微孔分析仪对吸附剂进行表征,探究吸附剂表面化学性质和孔径分布对焦化废水吸附差异相关性。结果表明:4种吸附剂表面性质相近,孔隙结构不同是其吸附性能差异的主要因素。比表面积:A_1(1723.59m^2/g)>H(1716.19m^2/g)>A_2(911.55m^2/g)>A_3(505.23m^2/g),平均孔径:A_1(5.14nm)>H(5.02nm)>A_3(3.81nm)>A_2(3.45nm)。Redlich-Peterson吸附等温线方程能更好地拟合吸附数据。分子量分布、UV_(254)、SUVA和EEMs说明微孔面积较大的A_1和A_2优先吸附低分子量(<1000)有机物,A_3和H能够回收高分子量(1000~0.45μm)有机物,降低废水芳香构造化程度。焦化废水TOC中94.29%的有机物分子量小于10000,微孔(<2nm)和较小中孔(2~10nm)更适合用焦化废水吸附处理。上述研究指出,吸附材料、孔结构与孔径分布、焦化废水性质、有机物分子结构之间存在相关性,通过性质的匹配来实现废水预处理优化的吸附分离工艺。

Four kinds of carbonaceous sorbents including wood （A1）, coconut shell （A2）, coal （A3） and coke （H）, with different pore structures were selected for the static adsorption of total organic carbon （TOC） in coking wastewater. The influences of adsorption capacity, molecular weight and other factors on the adsorption performance were investigated. For the purpose of fully understand the correlation between surface chemical properties and pore size distribution of carbonaceous sorbents and its adsorption performance toward coking wastewater, the adsorbents were characterized by Fourier transform infrared spectrometer（FTIR）, Brunauer-Emmett-Teller （BET） and other analysis means. The results showed that the above four adsorbents had similar surface characteristics. Pore structures ofadsorbents were the main factors that affected the adsorption performance. BET surface areas： A1（1723.59m2/g）〉H（1716.19m2/g）〉A2（911.55m2/g）〉A3（505.23m2/g）, average pore diameter： A1（5.14nm）〉H（5.02nm）〉A3（3.81nm）〉A2（3.45nm）. The adsorption behavior could be well described by Redlich-Peterson adsorption isotherm equation. The investigation about the molecular weight distribution, UV254, SUVA, and EEMs indicated that A1 and A2 with large micropore area preferentially adsorbed low molecular weight organics, while A3 and H could refractory high molecular weight organics, reducing aromatic structure degree of coking wastewater; 94.29% organic matter in the TOC of coking wastewater was less than 10000. Carbonaceous sorbent with micropores（〈2nm）and small mesopores（2-10nm）were more suitable for the treatment of coking wastewater. All these findings indicated that correlation was existed in the pore structure, pore size of the sorbent materialand properties of coking wastewater as well as the molecular structure of organic matter. Therefore, adsorption and separation process with optimization of wastewater pretreatment can be achieved by matching the properties of sorbent and wastewater.