| According to the latest statistics, more than16%of China’s arable land has beenpolluted by heavy metals, one of the major pollutant sources is waste watercontaining heavy metals, therefore, the treatment of heavy metal wastewater isimminent. The silicone material is favoured because of its large surface area, porousstructure and good adsorption properties. In this paper, using water glass and sulfuricacid as raw materials to prepare high adsorption activity silicone by the method ofadding acid stepwise, the procedure comprising a series of processes such as reaction,standing and aging of gel, filtering, washing, ethanol washing, drying and calcining.The article investigated the influence of various factors in the procedure on productperformance, and optimized the experiment technology, to explore the optimumconditions. Next took advantage of cheaper chloropropyltrichlorosilane to bond withhydroxyl groups which is on the surface of homemade silica,then correspondingadsorption material containing sulfydryl was obtained via sulfhydrylation by reactingwith potassium hydrosulfide, after that, explored the adsorption properties of theadsorbent containing sulfydryl for heavy metal ions. Following conclusions weremade in this paper:1. Through analyzing the single factor experiments and the orthogonalexperiments to determine the optimum technological conditions for preparing highadsorption activity silica, the result showed that the optimal conditions were asfollows: the concentration of sodium silicate was11%,the volume ratio of sulfuricacid quickly added to the total sulfuric acid was0.3, the concentration of sulfuricacid was6.5mol/L, the concentration of surfactant was3%, the reaction temperaturewas70℃, the pH value of reaction endpoint was3, aging at a temperature of60℃for24hours, calcining at600℃. Under these optimum conditions for preparing,theDBP of the products obtained is3.75ml/g, and the infrared spectroscopy has showedobvious characteristics of silica, the XRD analysis of the sample showed offamorphous structure, and the specific surface area was377.54m2/g.2. Let silica gel prepared under optimum conditions react with chloropropyl trichlorosilane and potassium hydrosulfide to prepare modified silica and the analysisof infrared spectrum had found significant C-H vibration which indicated themodification was successful. The TOC analysis and elemental analysis of themodified samples found that the total organic contents of CP-silica gel and SH-silicone were8.98%and7.03%respectively, the sulfur content of SH-silica was4.99%, this revealed that in the modified process, loss percentage of carbon contentwas21.7%and the conversion rate of hydrosulfuryl was about80%.The modified silica gel and the raw silica gel were used to carry out adsorptiontest of lead under the same conditions, then compared the texts discovered that themodified samples took12hours to reach adsorption equilibrium, while the raw silicagel took around4h, videlicet, from the point of removal efficiency, the adsorptionefficiency of sulfhydryl silica gel for Pb2+could reach to more than99%, while theraw silica gel only about15%.This indicated that the adsorption efficiency of silicagel had been greatly improved after modified.In the text of using modified silica gel to adsorb mercury, the adsorptionequilibrium time became longer with the increase of initial concentration when theinitial concentration of mercury varied between5-50ppm. Absorption reactionsubstantially reached equilibrium in10hours and the removal efficiency of mercuryof various initial concentration could reach up to over90%after24hours. Theadsorption efficiency of mercury increased with increasing pH value, but when pHvalue was greater than7the adsorption efficiency was essentially the same. With theconcentrations of mercury increasing, the saturated adsorption capacity of mercuryhad been an increase,and the adsorption capacity of the sample was48mg/g. |
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