Advanced Materials Research Vol. 414

Abstract: Tailings dewatering is an important part of the tailings disposal. Sludge dehydrant is a kind of important auxiliary agent in improving the tailings dehydration dehydrated efficiency in tailings enrichment dehydration. The paper reviews that the preparation and application of special flocculant of specialized flocculants for tailings water treatment. And it points out the development tendency of the specialized flocculants for tailings water treatment. Cationic polyacrylamide as one of dewatering agents is a suitable mean to solve tailings dewatering problem.

Abstract: Use some contaminated site (D-block) in Chongqing of China as the experiment site, this paper studies effects of different sampling density (layout grid spacing) on the contaminated area and determination of contaminated boundary in system layout method of environmental monitoring, and then discusses the relationship between sampling density and contaminated distribution in system layout method according to the experiment result. The experiment result indicates that: in a certain range, increase the sampling density, contamination distribution will be more accurate; too big sampling density is not practical; for the common sites with unknown or large-range contaminated distribution, 10m×10m is the recommended layout sampling density.

Abstract: Two thiol collectors, sodium diethyldithiocarbamate (DDTC) and potassium ethyl xanthate (EXT), were adopted to stabilize hexavalent chromium from chromic slag. The average usage of each thiol collector is 62.5 μmol∙g^-1 in chromic slag. The leaching characteristic of Cr⁶⁺ in chromic slag was analyzed according to the acidic extraction process with the toxicity characteristic leaching procedure (TCLP) and the procedures of extraction in water with the horizontal vibration method (HMV). Under the 0.1 mol∙L^-1 TCLP and HMV conditions, we compared them with FeSO₄ and found that two thiol collectors presented better stabilization effects for Chromium (VI) from chromic slag, especially the effect by DDTC is more stabilized than that by EXT. The rate of their stabilized treatments is 78.42% and 83.18%, respectively, which both are obviously higher than that by FeSO₄. Heavy metal-thiol collectors such as flocculent mass is more stabilized under the neutral and alkalized conditions (pH>8), but it may be partly dissolved under the acidic conditions (pH<6) and the leaching amount of Cr⁶⁺ from chromic slag will increase quickly with pH decreasing.

Abstract: Large amounts of industrial hazardous waste (IHW) are generated with the rapid economicgrowth in Chongqing Municipality. The generation of IHW was 355994.12t in 2010 and made up 1.25% of industrial solid waste (ISW). Huge varieties and complex components of IHW make it difficulty in its management, which causing serious environmental problems. In this paper, the status of IHW generation, disposal and management was analyzed from 2006 to 2010. Moreover, the pollution prevention measures are proposed for the purpose of protecting the ecological environment

Abstract: This paper is about the migration of the total petroleum hydrocarbon (TPH) contamination, which concludes the migration rule of the TPH contamination through designing indoor soil column leaching experiment. Through researching the migration concentration of different components of TPH, experiment concludes that different components have different relative transfer abilities in typical soil, and the transfer ability has an inverse relation to the molecular weight and the ring numbers of aromatic hydrocarbon. The purpose of this research is to provide guidance to nonproliferation and remediation of the petroleum contamination.

Abstract: It studied the geological properties and contamination characteristics of soil from contaminated sites of typical chromate plants in western plateau of China. The results indicated that in the shallow part of 0-4m, it was mainly loess-like soil and in the depth of 4-18m, it was mainly gravels and pebbles. The soil had better permeability and ex-situ washing treatment is recommended. The soil was severely contaminated and the concentration of chrome (Ⅵ) was as high as 16,000mg/kg. Based on the analysis, it developed a two-stage demonstration project of countercurrent ex-situ washing plus chemical stabilization with daily capacity of 20m³ soil and a demonstration project of chemical reduction and precipitation plus advanced treatment of filter bed with daily capacity of 200m³ wastewater. After treatment, the concentration of chrome (Ⅵ) in soil was less than 100mg/kg and that in water was reduced to below 0.05mg/L from 1,000mg/L, which can meet the requirements of third-grade groundwater quality standard.

Abstract: Based on the process of health risk assessment for Cd contaminated sites, study the relationship between exposure duration and recommended target of soil remediation. This paper discusses the changes (from 7.7 mg/kg to 5.0 mg/kg, from 9.1 mg/kg to 3.8 mg/kg) of recommended target for soil remediation when the exposure duration has large changes (EDa ranges from 6a to 36a, EDc ranges from 1a to 12a). The results point out that both EDa and EDc have effects on recommended target of soil remediation, and in general, exposure duration and recommended target of soil remediation vary inversely.

Abstract: Based on early environmental investigation of the contaminated site, this paper conducts risk assessment for the particular Cd-contaminated site (S-block), acquires the remediation scope of contaminated soils and puts forward a corresponding remediation project accordingly, and then monitors and compares the Cd content before and after remediation. The results indicate that the risk assessment can reflect contamination distribution and contamination level of S-block, which provides a reliable basis for targeted remediation, and the monitoring results show that S-block has been remedied effectively.

Abstract: Urban soil is a compositional part of urban ecosystem playing a vital role in urban sustainable development for it functions importantly in ecological, environmental and economical area and it is urban pollutants’ source and concourse. This paper systematically concludes and expounds a series of research achievements about soil heavy mental contamination, micro-organic material pollution, the environmental and healthy risk assessment of urban soil pollution of domestic and foreign research in recent 10 years. The development focus and tendency of urban soil pollution research are provided on this base for supplying vital scientific clues for improving urban ecological environment.

Abstract: In this paper, contaminated soil collected from chromium waste landfill has been investigated, and the cement-based solidification/stabilization (S/S) of the chromium-contaminated soil was also discussed by single-factor and orthogonal experiments. The cement can effectively solidify Cr in soil, and this can be classified into three stages: slow improvement, accelerated improvement, and technically stable limit. It is technically and economically feasible when the proportion of cement is 30%–40%. Cr (VI) dissolution can be further reduced through adding up appropriate stabilizer in the cement briquette. The results of orthogonal experiments indicate that cement proportion is the most important factor of Cr S/S, then the ratio of stabilizer, and the kind of stabilizer is the least important. In analyzing the factors of cement-based S/S of the polluted soil, the optimum parameters are as follows: the ratio of cement to soil is 35% and that of FeSO₄ (stabilizer) is 2.5%. Moreover, the ultimate leaching concentration of Cr (VI) is 0.89 mg/l and curing rate is 98.27%.