不同黏土矿物材料对Cd2+的吸附特征

探讨了在不同矿物投加量、不同振荡时间、不同Cd2 质量浓度、不同矿物颗粒细度和不同pH值条件下,钠基膨润土、膨胀蛭石和沸石3种黏土矿物对Cd2 的吸附效果,并比较了3种黏土矿物对Cd2 的吸附差异性.结果表明:具有可膨胀层间的黏土矿物对溶液中Cd2 的吸附量不仅仅由单一的阳离子交换量决定;Cd2 在矿物表面的吸附过程是个迅速的过程,在10 min内即可完成;黏土矿物颗粒细度不同,对Cd2 的吸附率不同,但并非颗粒越细吸附量越大;就实验所采用的3种黏土矿物而言,在较低矿物投加量条件下,其对Cd2 的吸附能力从大到小依次为钠基膨润土、沸石、膨胀蛭石;较高的pH值有助于黏土矿物对溶液中Cd2 的吸附,但考虑到实际操作的其他因素,不能把pH值调得过高.

Study on the characteristic features of Cd2+ adsorption by different clay minerals

The present article is inclined to introduce our study results of the characteristic features of adsorption produced by different clay minerals on Cadmium through drinking water and human foods.In our experiment,three kinds of clay minerals,that is,Na-bentonite,expansible vermiculite and zeolite,and each kind of mineral materials were chosen with 4 or 5 different diameters.The results of our experiments have shown that the cation exchange capacity of the minerals is not an exclusively crucial factor for the adsorption of interlayer-expansible clay minerals to Cd in the solution.Rather,it is the Na-bentonite,whose granules are of diameter of 0.074 mm that have the greatest Cd adsorption.However,the expansible vermiculite of 0.165 mm just has the least Cd adsorption.Under the same size of granule,the Cd adsorption capacity of the three kinds of clay minerals can be shown in the following order:Na-bentonite > zeolite > expansible vermiculite.Besides,the adsorption velocity of the clay minerals to Cd proves to be so high that it is only 10 minutes of shaking that would be enough for it to obtain the equilibrium state.Moreover,the results of our experiments also indicate that pH value has strong influence on the Cd adsorption of clay minerals,and in turn,higher pH value would help to increase the adsorption capacities of all the three clay minerals to Cd.However,for the time being,it seems difficult for human operators to regulate the pH too high in practical uses when all the other factors are taken into full account.