铬渣处理技术与综合利用现状研究

针对国内铬渣污染现状,介绍了铬渣污染途径及危害,列举了铬渣无害化处理的技术,包括酸性还原法、碱性还原法、碳还原法、微生物解毒法、干式还原法和固化/稳定化处理法。对铬渣的解毒方法和固化/稳定化技术进行了比较。概述了铬渣的部分利用现状。铬渣用于制砖、铬渣用于制造微晶玻璃、铬渣作为玻璃着色剂、铬渣用于制造耐火材料、铬渣用作炼铁熔剂、铬渣用于制钙镁磷肥。总结了目前铬渣处理技术与利用现状的不足。     

铬渣烧结炼铁的应用研究

铬渣产量大、毒性剧烈,是严重污染环境和危害人类健康的危险废物。本文介绍了铬渣烧结连铁的解毒原理和工艺处理过程,从理论和实践两个方面阐述了铬渣烧结炼铁的可行性。研究对比了掺加铬渣前后成品矿的浸出毒性和＂三废＂排放情况,得出了铬渣烧结炼铁的最佳掺加量。结果表明,控制铬渣掺加量在1.5%以内,成品矿的性能指标符合相关标准要求,所排放的污染物能达标排放。从而达到铬渣解毒目的,实现铬渣的资源化和无害化。     

铬渣制钙镁磷肥对农作物生长及铬残留量影响

用铬渣代替蛇纹石制钙镁磷肥是化工、冶金部门将铬渣“化害为利”综合利用的有效途径之一。为了探讨铬渣制钙镁磷肥对农作物生长和产品的影响、对农作物铬残留量影响和铬在土壤中的残留,我们进行了试验。 一、材料和方法 本试验采用土壤一次添加不同用量的铬渣制钙镁磷肥与普通钙镁磷肥进行盆栽与小区田间对比试验,以确定铬渣制钙镁磷肥对农作物生长与铬残留量影响。     

铬渣污染控制及综合利用的研究

铬渣是强碱性危险废物,对环境污染严重。分析了铬渣的来源与危害,提出从减少产渣量、铬渣中Cr6+回收、铬渣的无害化、综合利用及安全填埋等途径控制其污染。     

化工铬渣中铬的存在形态研究

通过铬在原铬渣、消解铬渣和消解解毒铬渣中存在形态的研究，揭示了铬渣中的铬以水溶态，酸溶态、稳定态、结晶态和残余态等５咱形态存在，其中稳定态，结晶态和残余态中的铬含量为１．４－１．５ｍｇ／ｋｇ渣，基本相等，在自然条件下，这３种形态的铬都比较稳定，而原铬渣与消解铬渣中水溶态与酸溶态的铬占总铬量的４０％，这部分铬容易通过各种途径释入到环境中造成污染。研究还表明经蒸压消解的铬渣较大幅度地提高了水溶态６价铬     

铬渣渗滤液处理方法及应用现状

铬渣产量大、毒性剧烈,是严重污染环境和危害人类健康的危险废物。铬渣的环境污染问题已经引起了国家的高度重视,要求2010年底前,所有历史堆存铬渣实现无害化处理。铬渣堆放所产生的含铬渗滤波已对周围的土壤、地下水乃至居民身体健康造成危害。因此,在铬渣得到治理的同时,含铬渗滤液必须得到有效治理。系统评述了铬渣渗滤液的各种治理技术和应用现状,并展望了含铬废水处理技术的发展前景。     

高温自蔓延还原解毒固化铬渣技术研究

采用高温自蔓延技术处置铬渣,探讨了高温自蔓延技术还原解毒固化铬渣的机制。以铝粉和三氧化二铁作铝热剂,与铬渣充分混合,用镁条点燃引发自蔓延反应,最终得到铬渣固化体。实验结果表明:高温自蔓延技术能有效固化铬渣,铬渣的掺渣率高达44.94%。浸出实验结果表明:A组(铬渣原样)铬渣固化体总铬浸出浓度未检出;B组(铬渣原样+重铬酸钾)铬渣固化体总铬浸出浓度为0.117 76 mg/L,远远低于国标(GB 5085.3-2007)限值15 mg/L,六价铬浸出浓度未检出。XRD分析表明:铬渣还原解毒固化机制主要是六价铬在自蔓延反应中被还原为三价铬,再与其他金属化合物在高温熔融状态下生成含铬尖晶石,铬以离子键Cr—O的形式参与尖晶石的晶格形成。     

解毒铬渣安全性研究

用扫描电镜、比表面测定仪、X-射线衍射仪测定了铬渣及解毒铬渣的表面形貌、比表面及物相组成。在模拟环境条件下对解毒铬渣进行了浸出毒性试验,结果表明,解毒铬渣在环境条件下是安全的。      

铬渣处理方法研究现状

铬元素是现代工业最重要的原材料之一,但有钙焙烧工艺产生的铬渣会对环境和人体健康产生巨大的危害。介绍和分析了国内外铬渣处理处置的主要方法及其优缺点,国外集中于铬渣的无害化处理,而国内则以铬渣的综合利用为主。在越来越注重环境效益和资源利用率的今天,铬渣的综合利用更能获得经济效益和环境效益的双赢。     

浅谈铬渣解毒技术

介绍了铬渣污染状况,对比分析了10余种铬渣解毒技术的优缺点,并且重点论述了旋风炉附烧铬渣工艺过程及其技术特性。研究表明,旋风炉附烧铬渣具有吃渣量大,解毒彻底等优点,是一种具有推广价值的新型铬渣解毒技术。      

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.     

Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment

Zeolite synthesized from fly ash （ZFA） without modification is not efficient for the purification of NH4＋ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 （≥0.9 mol/L） resulted in a limited maximum phosphate immobilization capacity （PIC）. It was concluded that through a previous mild acid treatment （e.g. 0.01 mol/L of H2SO4）, ZFA can be used in the simultaneous removal of NH4＋ and P at low concentrations simulating real effluent.