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采用液相沉淀法将氢氧化镧和天然沸石进行复合,制备得到镧-沸石复合材料,并通过批量吸附实验考察了该复合材料对水中磷酸盐的吸附作用,特别是考察了该复合材料去除水中低浓度磷酸盐的影响因素.结果表明,当制备复合材料时沉淀pH值为5~7或13时,复合材料对水中磷酸盐的吸附能力较差;当沉淀pH值控制为9~12,复合材料对水中磷酸盐的吸附能力较好,且当沉淀pH值由9增加到11时,复合材料的吸磷能力明显增加,继续增加pH值由11~12时,复合材料的吸磷能力基本不变.沉淀pH值为11时制备的镧-沸石复合材料对水中磷酸盐的吸附平衡数据可以较好地采用Langmuir模型加以描述,根据Langmuir模型预测的最大磷酸盐吸附量为44 mg·g~(-1)(磷酸盐溶液pH 7和反应温度30℃);该复合材料对水中低浓度磷酸盐的吸附动力学可以较好地采用准二级动力学模型加以描述.当磷酸盐溶液pH值由3增加到8时,沉淀pH值为11条件下制备得到的镧-沸石复合材料对低浓度磷酸盐的吸附能力增加,继续增加磷酸盐溶液pH值时,该复合材料对磷酸盐的吸附能力下降;与磷酸盐溶液共存的氯离子和硫酸根离子不会抑制该复合材料对低浓度磷酸盐的吸附,而碳酸氢根离子则会略微抑制该复合材料对磷酸盐的吸附;与磷酸盐溶液共存的腐殖酸会抑制该复合材料对水中低浓度磷酸盐的吸附.当磷酸盐溶液pH值为7时,沉淀pH值为11时镧-沸石复合材料吸附磷酸盐的机制主要为配位体交换作用.因此,沉淀pH值为11时制备得到的镧-沸石复合材料适合作为吸附剂去除水和废水中低浓度磷酸盐.
The lanthanum-zeolite composite was prepared by liquid-phase precipitation of lanthanum hydroxide and natural zeolite, and the adsorption of phosphate on water was investigated by batch adsorption experiments. In particular, The results showed that when the pH value of precipitates was 5 ~ 7 or 13, the adsorption capacity of phosphate in water was poor. When the sedimentation pH was controlled at 9 ~ 12, The adsorption capacity of phosphate on water is better, and when the pH value of the precipitate is increased from 9 to 11, the phosphorus uptake ability of the composites increases obviously. When the pH is increased from 11 to 12, the phosphorus uptake capacity of the composites is basically not The adsorption equilibrium data of lanthanum-zeolite composites prepared by precipitation at pH 11 can be well described by Langmuir model. The maximum phosphate adsorption capacity predicted by Langmuir model is 44 mg · g ~ (-1) -1) (phosphate solution pH 7 and reaction temperature 30 ℃). The adsorption kinetics of low concentration phosphate in water can be well described by quasi-second order kinetic model.When pH value of phosphate solution is controlled by 3 increase By 8:00, the adsorption capacity of lanthanum-zeolite composite prepared under the condition of pH value of 11 was higher than that of low-concentration phosphate, and the phosphate adsorption capacity of the composites decreased when the pH of phosphate solution was increased. The chloride ions and sulfate ions coexisted in the phosphate solution did not inhibit the adsorption of low concentrations of phosphate on the composites while the bicarbonate ions slightly inhibited the phosphate adsorption on the composites. When the pH value of phosphate solution is 7, the mechanism of adsorption of phosphate by lanthanum-zeolite composites is mainly ligand exchange. Therefore, lanthanum-zeolite composites prepared by precipitation at pH 11 are suitable as adsorbents to remove low concentrations of phosphate in water and wastewater.