水溶液中六价铬在碳纳米管上的吸附

针对用碳纳米管对水溶液中六价铬的吸附净化进行了研究, 考察了溶液浓度、溶液pH值、共存的三价铬离子等因素对吸附行为的影响. 实验结果表明, 碳纳米管在室温下对于六价铬的吸附量随着平衡浓度的增大而升高, 在铬浓度为493.557 mg•L−1时碳纳米管吸附量达到最大值为532.215 mg•g−1; 六价铬的浓度在300~700 mg•L−1的范围内, 碳纳米管对铬的吸附量变化不大；大于700 mg•L−1时, 随着铬的平衡浓度的升高碳纳米管对铬的吸附量降低, 铬浓度为961.074 mg•L−1时, 碳纳米管吸附量降至194.631 mg•g−1. 在pH值为2~7的范围内, 碳纳米管对六价铬的吸附量随着溶液pH值的减小而增大; 而在碱性条件下, pH值对碳纳米管吸附六价铬的影响不大. 溶液中存在三价铬时, 碳纳米管对六价铬的吸附量明显降低, 表明三价铬与六价铬有竞争吸附. 此外, 活性炭的对比吸附实验表明, 在低浓度时, 譬如在六价铬浓度为190 mg•L−1吸附时, 碳纳米管对铬的吸附量约为活性炭的6倍；而在高浓度下, 譬如六价铬浓度为493 mg•L−1时, 碳纳米管对铬的吸附量约为活性炭的2倍.

Adsorption of Hexavalent Chromium Ions on Multi-wall Carbon Nanotubes in Aqueous Solution

Carbon nanotubes (CNTs) were employed to remove toxic hexavalent chromium ions from aqueous solution. Effects of concentration of hexavalent chromium, solution pH, coexistent trivalent chromium in the solution on the Cr(VI) adsorption were examined. The results show that the adsorption capacity of Cr(VI) on CNTs increased with increase of Cr(VI) concentration, and then reach a plateau between 300~700 mg•L−1 of Cr(VI); the maximum value of 532.215 mg Cr(VI) per g CNTs was achieved at the Cr(VI) concentration of 493.557 mg•L−1, and followed by a decrease at still higher concentration of Cr(VI). The capacity was also significantly affected by the pH value of the solution between 2 and 7, and little change was observed above pH value of 7. Addition of Cr(III) into the Cr(VI) solution could decrease the Cr (VI) removal capacities because of their competitive adsorption on CNTs. Under the same experimental conditions, CNTs showed an adsorption capacity of Cr(VI) 6 times as large as the commercial activated carbon at 190 mg•L−1 of the concentration of Cr(VI).