| Heavy metal derived from mine tailing, mine processing and metallurgy, and dust during the mining is the main pollution in mining area. Heavy metal can release from minerals after weathering, oxidation, and leaching and then step into surface water, soil, and ground water by irrigation, sedimentation, and permeation, which would result in the pollution of soil and groundwater. As we known, heavy metals are hard to be decomposed and easy to enrich and accumulate. This behavior will seriously affect the ecological species, the structure and function of ecosystem, and pollute the crops and aquatic products. In addition, heavy metals existing as different chemical state will indirectly or directly threaten human beings’life by food chains after they step into environments.According to the incomplete statistics, the quantity of metal mine identified metal mineral occurrence of Anhui province comes to960; identified storage comes to12.99billion ton, in which mining reaches500, stopped or closed comes to250, and unmining comes to210. Therefore, it is becoming more and more important to prevent and cure the heavy metal pollution. The metal mines mainly distribute in Luan, Maanshan, Hefei, Tongling, Chizhou city, etc, where Cu2+、Cd2+、Hg+、 Pb2+、Zn2+、Cr6+are found as the main metal pollutions and have been attracting the attention of experts, scholars, and governments.Sedimentary palygorskite is documented having a good adsorption capacity to heavy metals; iron powder prepared by reducing goethite possesses great reductive activity to nitrate and nitrite, and good adsorption capacity to phosphate. In addition, montmorillonite is also proved to be a good adsorbent to removal heavy metals. Therefore, in order to study the efficiency of mineral adsorption to remove heavy metals; to broaden the application field of palygorskite, goethite and montomorillonite, and explore the material properties of minerals; to explore new materials for environmental protection to effectively prevent and cure heavy metal pollutions of mining area and improve the sustainable development of economy, society and ecological environment. In the present work, we analysized the status of exploitation and utilization of Anhui metal mine resource and its distribution characteristics. Based on the possible pollution types of heavy metal, we studied the efficiency of three kinds of iron powders, two kinds of palygorskites and two kinds of montomorillonites to remove eight kinds of heavy metal ions from aqueous solution and the removal mechanism.In this thesis, the status of exploitation and utilization of Anhui mine resources, especially for the metal mine resources, was analysized. The distribution characteristics of Anhui mine resources and mining wasteland were drawn using Arcgis software and the key zone of prevention and cure was confirmed. What was mostly important, the efficiency of iron powder prepared by reducing natural goethite and synthetic goethite, commercial iron powder, sedimentary palygorskite, hydrothermal palygorskite, Na-montomorillonite and Ca-montomorillonite to remove Pb2+、Zn2+、 Cu2+、Co2+、Cd2+、Hg+、Ag+、Cr6+was investigated based on the analysis results above. In addition, pseudo-second-order kinetic model, Langmuir and Freundlich isotherms, and adsorption dynamic were used to analysize the effect of adsorption time, heavy meatal initial concentration and adsoption temperature on removal of heavy metals using seven kinds of materials. The solution pH of some materials before and after adsoption was measured. Eventually, XRD, FE-SEM/EDS, TEM, FT-ATR, FT-IES, TG/DTG, BET, etc, were utilized to characterize the seven materials before and after adsorption, in order to study the the removal mechanism. The main conclusions obtained from the analysis and experiments are listed as follows:1. Based on the analysis of the status of exploitation and utilization of Anhui mine resources, it can conclude that the order of the metal mine storage is Luan city>Maanshan city>Hefei city>Tongling city>Chizhou city>Huangshan city. These city was speculated as the key prevention and cure area of heavy metal pollution.2. Iron powder prepared by reducing natural goethite (NG-ZVI) and synthetic goethite (HG-ZVI), and commercial iron powder (CIP) were characterized using XRD, TEM, SEM, TG/DTG, etc. The results showed that NG-ZVI with a size of nano scale iron powder and HG-ZVI with a size of several hundreds of nanometer were prepared by reducing goethite in hydrogen. The CIP was a kind of micron scale iron powder.3. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using three kinds of iron powder was investigated. Totally, the order of removal efficiency was HG-ZVI>NG-ZVI≈CIP. The adsorption capacity of HG-ZVI to eight heavy metals was higher that of NG-ZVI and CIP. The adsorption capacity of NG-ZVI to Cr6+was higher than that of CIP, however, The adsorption capacity of CIP to Cu2+was higher than that of NG-ZVI. It was suggested that the surface area was key factor limiting the activity of CIP, and the impurity, isomorphous substitution and aggregation were the factors affecting the activity of NG-ZVI.4. The removal mechanism showed that three kinds of iron have a reductive activity to Cu2+. Cu2+was reduced into Cu0by CIP, Cu2+was reduced into Cu+and then into Cu0by NG-ZVI or HG-ZVI. NG-ZVI and HG-ZVI can reduce Ag+into Ag0quickly, In addition, Cr6+can be degraded into Cr3+by HG-ZVI, which decreased the toxicity. Adsorption or/and precipitation is/are regarded as the main mechanism for three kinds of iron powder removal of Pb2+、Zn2+、 Co2+、Cd2+.5. Sedimentary palygorskite (SPG) and hydrothermal palygorskite (HPG) were characterized using XRD, FE-SEM/EDS, FT-ATR, FT-IES, etc. The results showed that SPG contained some quartz and dolomite, was kind of Fe-substituted palygorskite, and possessed large surface area and total pore volume. HPG was highly pure, however, had a lower surface area and total pore volume than that of SPG6. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using SPG and HPG was investigated. The results showed that HPG had a better adsorption capacity to selected heavy metals than that of SPG. Nevertheless, the both palygorskite has a bad capacity to Cr6+. It was suggested that the characteristic of Fe substitution, large surface area and morphology of SPG provided benefit conditions for removal of heavy metals. The induced metal precipitation and adsorption were regarded as the main mechanism for removal of heavy metals by SPG.7. Na-montomorillonite (Na-M) and Ca-montomorillonite (Ca-M) were characterized by XRD, TG/DTG, and BET, etc. The results showed that Ca-M was purer than that of Na-M which contained some quartz and feldspar. The interlayer water of Ca-M was more than that of Na-M. The interlayer space, surface area and total pore volume of Ca-M were also larger than that of Na-M.8. The effect of adsorption time, initial concentration, adsorption temperature on removal of heavy metals using Na-M and Ca-M was investigated. The results showed that Na-M had a better adsorption capacity to selected heavy metals than that of Ca-M. Nevertheless, the both montomorillonite had a bad capacity to Cr6+, which was contributed to the different removal mechanism. The solution pH before and after adsorption was measured at a short interval. The adsorbed Na-M and Ca-M were characterized using XRD and the concentration of Na+and Ca2+before and after adsorption was detected using ICP-MS. The results showed that ion exchange was the mian mechanism for removal of heavy metals by Ca-M; however, induced metals precipitation was regarded as the other mechanism for removal of heavy metals besides ion exchange.9. All the results showed that adsorption and precipitation were proposed as the mian mechanism for removal of Pb2+、Zn2+、Co2+、Cd2+by iron powder. Besides, reduction participated the removal process of Cu2+、Ag+and Cr6+by HG-ZVI. The removal mechanism of iron powder was different from that of montomorillonite and palygorskite. Adsorption and induced precipitation were suggested as the mian mechanism of palygorskite, while ion exchange and induced precipitation were regarded as the mechanism of montomorillonite. In addition, the removal capacity of Na-M was higher that that of SPG. |
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