Utilization Of Adsorbents Prepared From Agricultural Solid Wastes For Treatment Of Coking Wastewater

The article aims at treatment of coking wastewater, in which the effluent concentration ofCOD and NH3-N could not attain the national discharge standard after biological treatmentprocess. The adsorption technology which is known as a core environmental protectiontechnology could make up for the biological treatment when dealing with toxic and difficultdegradable pollutants and achieves rapid separation of the contaminants. The adsorptiontechnology development is limited because of its high cost, so the key technology is searchingfor an inexpensive raw material for adsorbent. Agricultural solid wastes have been proven tobe potential raw materials for adsorbents.In the present study, four kinds of adsorbents prepared by rice bran, corn stalk, orangepeel and peanut shell were selected to do the comparison of COD and COD removal rateduring treating coking wastewater. The result indicates that the adsorbent prepared by peanutshell has an outstanding ability to purify wastewater, which was prospected for successivestudies. As the best preparation condition that was investigated in the experiment, theadsorbent was carbonized at400℃for30min, chemical activated by15%phosphoric acid ata1:3ratio of solid to liquid. The experimental results indicate that at a dose of20g·L-1andthe temperature of25℃, the adsorbent prepared by peanut shell showed60%removal rate in8h adsorption time. pH does not much affect COD removal rate within the physical pH(6~9)of coking wastewater. The experimental isotherm data were according with the linearizedforms of Langmuir equations and pseudo-second-order model.Modification of peanut shell leads to an increase in the content of the surface oxygencontaining functional groups. However the specific surface area of modified peanut shellmeasured as7.16m2·g-1, was rarely increased. The GC/MS analyzed results of before andafter adsorption showed that the interaction of the surface oxygen containing functionalgroups and the hydrogen bond of phenols and the π-π interaction between aromatic ringsprobably operated as mechanisms of adsorption of peanut shell.Economic evaluation shows that the absorbent prepared by peanut shell has obviouseconomic benefits and broad prospects for application.