Experimental Study On Heavy Mentals In Water With Modified Activated Carbons

Heavy metal ions have great contribution to the pollution of water．In order toimprove the adsorption capability of heavy metal ions with activated carbon, the activatedcarbon is modified with relevant modifier.In the paper, modified activated carbon made of peach stone and coconut shell wereobtained after modified with manganese nitrate. The modified activated carbons (ACMnand ACM) were used to adsorb Cr(VI) and Ni(II) from aqueous solution in order to testtheir adsorption performances. The effects of different concentrations of modifier, solutionpH, dosages, adsorption time, initial concentration of adsorbate with ACMnand ACM wereinvestigated. Adsorption kinetics and isothermal adsorption characteristics as well as howthe loading and operation conditions of the adsorbent affects the removal of Cr(VI) andNi(II) in the water were studied. Then, the characteristics of morphology and surfacechemistry were investigated by Scanning Electron Microscope (SEM), Fourier TransformInfrared Spectroscopy (FTIR), Brunauer–Emmett–Teller surface (BET) and X-raydiffractometer (XRD). The followings are the main conclusions:①Peach stone activated carbons were modified with different concentrations ofmanganese nitrate. The results showed that the adsorption capacity for Cr6+was optimalwhen ctivated carbons were modified with0.03mol/L manganese nitrate. Coconut shellactivated carbon adsorption capacity was better than peach stone activated carbon, and theadsorption capacity of Cr6+was better than Ni2+.②The results showed that there were a lot of new hydroxyl and carboxyl groups onthe surface of the modified peach stone activated carbon, and the BET, pore volume andactivated adsorption quantities were significantly increased. The modified peach stoneactivated carbons loaded with MnO2, which represented the amount of2.07%wt.%. TheXRD pattern of peach stone activated carbon showed the typical amorphous carbonstructure with only the silicon dioxide and calcium carbonate diffraction peaks, the latticestructure had not shown significant change in modified peach stone activated carbon.③pH value of the solution has a great influence on the activated carbon adsorptionfor Cr6+and Ni2+. Under the low value of pH, the adsorption efficiency of Cr6+was high.Activated carbon adsorption capacity for Ni2+was increased with increasing pH value.Coconut shell activated carbon could adsorb Cr6+and Ni2+in heavy metals wastewater and the adsorption time lasted short time. The mainly adsorption process was carried out within40minutes, and the adsorption rate gradually slowed after40minutes.④The kinetic data were fitted by pseudo-first order, pseudo-second order andintra-particle diffusion models. The results could be well described by the pseudo-secondorder model and intra-particle diffusion models. Equilibrium adsorption data wereanalyzed by the Langmuir and Freundlich isotherm models. The adsorption of activatedcarbon for Cr6+and Ni2+were favorable.The results fitted better to the Langmuir modelthan to Freundlich model.