四种吸附剂材料对镉去除及硬水软化的研究

Study on effect of four adsorbents on removal of cadmium and hard water softening

以核桃壳和杏仁壳为原料,经高温热解成生物炭再利用酸、碱修饰对其进行改性制备成吸附剂材料,同时以矿物吸附剂(蛭石)和竹炭作为对比材料,比较了四种改性吸附剂对镉(Cd),以及对硬水中钙(Ca^(2+))、镁(Mg^(2+))的吸附性能,考察了吸附剂投加量对Cd去除和硬水软化处理效果的影响,初步探讨了吸附机制。结果表明:果壳生物炭经酸碱改性后吸附能力显著提升。竹炭和杏仁壳炭对Cd的吸附效果相当(去除率分别为99.2%,99.1%),核桃壳炭次之(93.8%),蛭石对Cd的去除受Cd浓度影响较大,而杏仁壳可以净化不同程度Cd污染废水。核桃壳和杏仁壳炭对Ca^(2+)和Mg^(2+)的吸附能力强,二者在最小投加量(1 g)时即可将水的硬度降至饮用水标准值(450 mg·L^(−1),以CaCO_(3)计)以下,对Ca^(2+)、Mg^(2+)的去除率最高可达83.6%,而竹炭和蛭石对硬水基本没有软化效果。因此,改性果壳生物炭可用于低浓度污染饮用水深度净化处理,在实际工艺设计时应根据参考水质标准特别考虑生物炭吸附剂的使用量。

In this study,walnut shell and almond shell were pyrolyzed into biochar and modified with acid or alkali to prepare adsorbent materials.At the same time,mineral adsorbent(vermiculite)and bamboo charcoal were used as comparative materials.The adsorption performance of four modified adsorbents on cadmium(Cd),calcium(Ca^(2+))and magnesium(Mg^(2+))in hard water was compared.The effect of adsorbent dosage on Cd removal and hard water softening was investigated,and the adsorption mechanism was discussed.The results showed that the adsorption capacity of the nutshell biochar modified by acid or alkali was significantly improved.The adsorption effect of bamboo charcoal and almond shell charcoal on Cd was comparable(removal rates of 99.2%and 99.1%respectively),followed by walnut shell charcoal(93.8%).The removal of Cd by vermiculite was greatly affected by the Cd concentration,while almond shell could purify wastewater polluted by Cd in different degrees.Walnut shell and almond shell charcoal had strong adsorption capacity for Ca^(2+)and Mg^(2+). Both of them reduced the hardness of water to the drinking water standard value (450 mg·L^(−1), calculated as CaCO_(3)) at the minimum dosage (1 g), and the removal rate of Ca^(2+) and Mg^(2+) reached up to 83.6%, while bamboo charcoal and vermiculite had no softening effect on hard water basically. Therefore, the modified nutshell biochar can be used for the deep purification of low-concentration polluted drinking water. In the actual process design, the amount of biochar adsorbent should be specially considered according to the reference water quality standard.