几种层状化合物对六价铬吸附性能的对比与讨论

Comparison and Discussion on the Adsorption Capacity of Several Compounds with Layered Structure

柱撑蒙脱石和有机蒙脱石对Cr(VI)的吸附容量分别为8.9和3.7mg/g,二者在吸附容量上的差别主要和它们的表面性质有关.双金属氢氧化物(LDH)结构层之间的CO3(2-)离子难以被Cr(VI)交换,其吸附容量为11.3 mg/g.双金属氧化物(LDO)能够从水溶液中获取阴离子和水分子,并恢复重建LDH的结晶结构,它对Cr(VI)的吸附属化学吸附,其吸附容量在一般条件下为73 mg/g.通过抑制溶解CO2对LDO吸附反应的干扰,它对Cr(VI)的吸附容量可达理论值.

Pillared montmorillonite (P-MMT), organic montmorillonite (O-MMT), layered double hydroxide (LDH) and layered double oxide (LDO) were prepared. Their adsorption performance on Cr (VI) was measured. The result shows that adsorbent capability (AC) of P-MMT and O-MMT is 8.9 and 3.7 mg/g respectively; both of them can be attributed to physical adsorption. Their surface characters, i.e., hydrophilic P-MMT versus hydrophobic O-MMT, are quite possibly responsible for the difference in AC. LDO's AC on Cr (VI) is 73 mg/g at room temperature, much higher than that of the other materials. After the adsorption, LDO's XRD pattern changes apparently, similar to the one of LDH. This demonstrates that LDO took anions from the solution to recover the crystal structure of LDH, and that the adsorption is chemical one. Theoretical AC of LDO on Cr (VI) calculated from the reaction formation is 152 mg/g. pH variation during the adsorption was observed. pH of the solution increased rapidly at the first few minutes, slowly from 5 to 180 minute, decreased a bit after that. The first two phases indicate the adsorbing progress, and the last one is quite possibly related with the interference of dissolved CO2. There are two ways to restrain the activity Of CO2, increasing Cr (VI) content and/or decreasing CO2 content. In the solution being boiled and isolated from air, LDO's AC on Cr-.(VI) can be as high as 157.1 mg/g. The part above the theoretical AC can regard as the contribution of physical adsorption.