Study On The Property Identification Of Solid Waste And The Change Rule Of Its Corrosiveness

According to the law of the people's Republic of China on the prevention and control of environmental pollution by solid waste,the state has issued the latest version of the directory of hazardous waste to guide the local management departments to carry out the supervision of hazardous waste.At the same time,for the solid waste not listed in the directory of hazardous waste,it is proposed to determine whether it is hazardous waste by means of attribute identification,which is the basis of environmental law enforcement It is believed that the legitimacy and effectiveness of environmental supervision are also the basis for ensuring the environmental safety of solid waste.Alkali sulfide is a very common chemical raw material,which has been widely used in leather unhairing agent,sulfide dye,metal smelting,rayon denitration and other fields.China is a large country in the production of alkali sulfide,and there are many alkali sulfide production enterprises in many provinces of China.Because of the abundant coal resources and the large production of mirabilite around,the production of alkali sulfide in our province is vigorous in a certain period.The alkali sulphide residue produced in the production process of alkali sulphide is not listed in the national list of hazardous wastes.When the environmental impact assessment agency carries out the environmental impact assessment of alkali sulphide production project,the alkali sulphide residue is defined as general industrial solid waste.The alkali sulphide production enterprise will landfill the alkali sulphide residue as general industrial solid waste or dispose it in other ways.Meanwhile,the ecological environment departments at all levels will In recent years,the environmental pollution accidents caused by the random landfilling of sulfurized alkali residue have aroused great attention of the central environmental protection supervision group.Due to the strong alkalinity of the alkali sulphide,there must be a certain amount of alkali sulphide in the slag which is not completely separated,so it can not be ruled out that the alkali sulphide waste slag may have corrosive or other harmful characteristics.On the premise that the properties of sulfurized alkali residue are not clear,if it is not piled up according to the specifications and discarded or disposed at will,it will pollute the air,soil and water body,and seriously threaten the local ecological environment and people's health.At present,scholars at home and abroad have not thoroughly studied the properties and management of alkali sulfide slag.In this study,the alkali sulfide slag produced by the alkali sulfide production enterprises in Gansu Province is taken as the research object.By collecting relevant literature and materials,investigating the development status of the alkali sulfide enterprises in China and our province on the spot,starting from the characteristics of the alkali sulfide production industry,we can understand its production scale,process type,alkali sulfide slag output and hazard characteristics,and take Shandan hongdingyuan Chemical Co.,Ltd Zhangye Jinshi Chemical Co.,Ltd.and Minqin Dongshun Chemical Co.,Ltd.are the representatives of three large-scale alkali sulfide production enterprises.A total of 362 samples of historical,new and incinerated waste residue are collected as the research objects.Through the analysis of the main components of raw and auxiliary materials,products and by-products used in the production process,combined with the production process,and in accordance with the general principles for the identification of hazardous wastes(GB5085.7-2007)and relevant specifications,through laboratory analysis,we can respectively draw the following conclusions: 1.Alkali sulfide slag does not involve organic pesticides,volatile and non-volatile organic compounds,raw materials are natural mirabilite and coal,and does not contain the national standard identification standard for hazardous wastes For all kinds of toxic substances listed in identification of leaching toxicity(gb5085.3-2007),randomly selected samples of nine heavy metals,copper,nickel,lead,chromium,cadmium,arsenic,mercury,barium and zinc,which may exceed the standard,were screened for leaching toxicity.All the tested items were lower than the standard limits,excluding the leaching toxicity.2.Raw and auxiliary materials,products and by-products in carbon reduction mirabilite process were not involved Toxic substances,excluding the characteristics of acute toxicity;3.Screening and testing of acid contact reactivity,and quantitative testing of the amount of hydrogen sulfide released,the test results show that the amount of hydrogen sulfide released is less than 500 The limit value of mg / kg excludes the hazardous characteristics of reactivity;4.Under one atmospheric pressure,randomly select samples for1000 ? high temperature ignition screening test,all samples are not ignited,excluding the hazardous characteristics of Flammability;5.Half of the death amount of the raw and auxiliary materials of alkali sulfide and waste residue related compounds are greater than the limit value of 200 mg / kg,excluding the hazardous characteristics of acute toxicity.In order to eliminate the above harmful characteristics,it is determined that the main harmful characteristic of alkali sulfide slag is corrosivity,and the corrosion characteristics of alkali sulfide slag under different environmental conditions of new generation and historical storage are studied by using the glass electrode method.According to technical code for identification of hazardous wastes(HJ / T 298-2007)and corrosivity identification standard for identification of hazardous wastes(GB)5085.1-2007),if the number of samples with p H ? 2 or p H ? 12.5 exceeds the limit value of corresponding standards in gb5085 and the number of samples is greater than or equal to the lower limit value of the number of samples exceeding the limit specified in the technical code for identification of hazardous wastes,it can be determined that the solid waste has such hazardous characteristics and belongs to corrosive hazardous waste.The results show that the samples with p H value ? 12.5 are higher than the limit value,so they are hazardous wastes.But in the later stage of different storage environment,the change rule of corrosion is different.Zhangye Jinshi Chemical Industry Co.,Ltd.historical alkali sulfide residue is still a hazardous waste because it is buried in a closed environment,and its corrosive p H value will not change significantly;Yama Nishiro Dingyuan Chemical Industry Co.,Ltd.alkali sulfide residue in full contact with oxygen in the exposed environment,with the passage of time,the alkali sulfide residue will be oxidized,and sodium sulfide will be converted into sodium thiosulfate or even sodium sulfate,its p H value gradually decreased,the number of samples exceeding the limit was lower than the limit,and it was transformed into general industrial solid waste.At the same time,the analysis of the newly generated and historical sulfurized alkali residue from the oxidation reaction(incineration)in Dongshun chemical company of Minqin shows that the samples with p H value exceeding the limit value are all lower than the limit value,which are general industrial solid wastes.It is concluded that the newly generated sulfurized alkali residue is hazardous waste and transformed into general industrial solid waste after oxidation.According to the research results of this project,it is proposed that the waste slag should be managed according to the hazardous waste after it is newly generated,and its corrosiveness can be reduced through oxidation reaction.After the value is reduced to within the limit,it is suggested that the general industrial solid waste management should be followed.At the same time,it is proposed that the environmental impact assessment organization should strictly determine the properties and management requirements of the waste slag In addition,through the research of this subject,the author has put forward to Gansu Province and even the national ecological environment department the attribute judgment of the alkali sulphide slag and the suggestions on the supervision of the alkali sulphide slag in the later stage and in different environments,which provides the scientific basis for the management of the alkali sulphide slag in the whole country.