互花米草厌氧发酵渣活性炭处理含镉废水的研究

The Treatment of Cadmium-contained Wastewater Using Activated Carbon Prepared from Anaerobic Digested Residue of S.alterniflora

采用静态吸附法,进行磷酸活化法不同剂料质量比(0.5～3.0)及活化温度(400～700℃)条件下制备的互花米草厌氧发酵渣活性炭对镉的吸附性能研究,考察不同初始浓度条件下活性炭对镉的平衡吸附量,旨在以吸附法治理含镉废水,探索吸附机理、影响因素、除镉吸附剂的最佳制备条件以及活性炭物化性质对镉吸附性能的影响。结果表明,镉的吸附性能与活性炭的制备条件有关,随着活化温度的升高,镉的吸附量逐渐增大,主要是因为高温条件下活性炭表面PO34-充当活性位点,促进镉的吸附。当剂料质量比为1.0,活化温度为700℃时,制备出的活性炭对镉的吸附性能最好,其最大吸附量可达38.91mg·g-1,远远高于商业活性炭。镉的吸附量随着溶液初始浓度的增加而增大,吸附等温线符合Langmuir方程。溶液pH和活性炭表面化学性质是决定镉吸附量大小的决定性因素,当溶液pH在2～4时,各活性炭对镉的吸附能力随pH的增加而增加。本文为含镉废水的处理提供了一种低价高效的方法。

This study was aimed to remove cadmium ions from aqueous solutions by adsorption. Studies on the adsorption of cadmium ions by different activated carbons with different physical and chemical properties were reviewed and the adsorption mechanism,influence factors,favorable activation conditions,etc,discussed in this paper. As adsorbent,activated carbons were obtained from anaerobic digested residue of S.alterniflora by phosphoric acid activation using different activation conditions：various activation temperatures（400～700 ℃） and different acid/precursor impregnation ratios（0.5～3.0）. Adsorption isotherms of cadmium ions were determined from solutions with different initial concentrate. Uptake of cadmium was found to be dependent on the preparation and activation procedure. This uptake increased as function of activation temperature for the H3PO4 activated carbons which could be attributed to the presence of some PO3-4 that may act as active centers contribute in cadmium adsorption. The results showed that an impregnation ratio and an activation temperature around 1 g H3PO4·g^-1 anaerobic digested residue of S.alterniflora and 700 ℃,respectively,were recommended as the best combination of operating conditions to prepare activated carbons for cadmium adsorption. The maximum adsorption capacity reached 38.91 mg·g^-1,which was superior to the ordinary commercial activated carbon on the market. The adsorption capacity of the investigated carbons increased with initial concentrate of solutions. The results revealed that obtained isotherms exhibited the model fitting according to Langmuir equation. The pH of solution and the surface chemistry of the carbons were found to play a decisive role in the uptake of cadmium ions from aqueous solutions rather than the carbon texture characteristics. It indicated that the investigated carbons removed appreciable amounts of cadmium ions which increased by increasing pH of solutions from 2 to 4. The data obtained provides a cost-effective technique in designing a treatment for cadmium-contained wastewater.