M, a particular industrial waste, was selected to detoxify chromium slag at a high temperature. The carbon remaining in M reduced Cr （ Ⅳ ） of Na2 CrO4 borne in the chromium slag to Cr （ Ⅲ ） in the solid phase re...M, a particular industrial waste, was selected to detoxify chromium slag at a high temperature. The carbon remaining in M reduced Cr （ Ⅳ ） of Na2 CrO4 borne in the chromium slag to Cr （ Ⅲ ） in the solid phase reaction, and its thermodynamics and kinetics were studied. The reduction process of Na2CrO4 by carbon produced CO, whiCh＇was endothermic. Under the experimental condition, the apparent activation energy was 4. 41 kJ·mol^-1 , the＇apparent order of reaction for Na2 CrO4 was equal to one, and the partial pressure of CO was only 0.22 Pa at 1 330℃.展开更多
Magnesium slag(MS)is one of the main industrial solid wastes produced by the magnesium industry.Solving the problem of its disposal has attracted much attention with increasing amounts of solid wastes generated in the...Magnesium slag(MS)is one of the main industrial solid wastes produced by the magnesium industry.Solving the problem of its disposal has attracted much attention with increasing amounts of solid wastes generated in the production of metallic magnesium.Because MS contains calcium(Ca),magnesium(Mg),and silicon(Si),some have tried to use MS as Si-Ca-Mg fertilizer or for soil amendment in agriculture.However,in the magnesium metallurgical process,some pollutant elements are introduced into MS,resulting in the enrichment of these pollutants in MS,such as arsenic(As),chromium(Cr),cadmium(Cd),mercury(Hg),copper(Cu),nickel(Ni),fluorine(F)and chlorine(CI).Research indicates that the enrichment of these pollutants can result in high levels,especially for Cd,Hg,Cu,Ni,F and CI(0-4,0-0.74,20-127,100-170,2277-14800 and 133-1000 mg kg1,respectively)in some MS in China.These levels are often far beyond the limits(S0.3,s0.5,≤50 and≤60 mg·kg-1 for Cd,Hg,Cu and Ni,respectively)of the Chinese Risk Screening Values for Soil Contamination of Agricultural Land based on the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(GB 15618-2018)or the critical reference values(<800 and≤200 for F and CI,respectively).The elements Hg,Cu,Cr and F(detected in MS leachate at 0.00023--0.0052,0.043--3.89,0.026-0.171,and 1.43-8.52 mg·L-1,respectively)also exceed the limits(Class IV-V)of the Chinese Standard for Groundwater Quality(GB/T 14848-2017).Based on the above results,it is suggested that without any pretreatment for reducing harmful pollutants MS should not be allowed to be applied for soil remediation or conditioning directly into farmlands in order to ensure soil health,food safety and environmental quality.展开更多
基金Item Sponsored by National Natural Science Foundation of China (50234040)
文摘M, a particular industrial waste, was selected to detoxify chromium slag at a high temperature. The carbon remaining in M reduced Cr （ Ⅳ ） of Na2 CrO4 borne in the chromium slag to Cr （ Ⅲ ） in the solid phase reaction, and its thermodynamics and kinetics were studied. The reduction process of Na2CrO4 by carbon produced CO, whiCh＇was endothermic. Under the experimental condition, the apparent activation energy was 4. 41 kJ·mol^-1 , the＇apparent order of reaction for Na2 CrO4 was equal to one, and the partial pressure of CO was only 0.22 Pa at 1 330℃.
基金The study is supported by the Special Public Welfare Project of Ministry of Science and Technology of China(1610132018013)the Special Program for Fertilizer Registration of Ministry of Agriculture and Rural Affairs of China(2130112).
文摘Magnesium slag(MS)is one of the main industrial solid wastes produced by the magnesium industry.Solving the problem of its disposal has attracted much attention with increasing amounts of solid wastes generated in the production of metallic magnesium.Because MS contains calcium(Ca),magnesium(Mg),and silicon(Si),some have tried to use MS as Si-Ca-Mg fertilizer or for soil amendment in agriculture.However,in the magnesium metallurgical process,some pollutant elements are introduced into MS,resulting in the enrichment of these pollutants in MS,such as arsenic(As),chromium(Cr),cadmium(Cd),mercury(Hg),copper(Cu),nickel(Ni),fluorine(F)and chlorine(CI).Research indicates that the enrichment of these pollutants can result in high levels,especially for Cd,Hg,Cu,Ni,F and CI(0-4,0-0.74,20-127,100-170,2277-14800 and 133-1000 mg kg1,respectively)in some MS in China.These levels are often far beyond the limits(S0.3,s0.5,≤50 and≤60 mg·kg-1 for Cd,Hg,Cu and Ni,respectively)of the Chinese Risk Screening Values for Soil Contamination of Agricultural Land based on the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(GB 15618-2018)or the critical reference values(<800 and≤200 for F and CI,respectively).The elements Hg,Cu,Cr and F(detected in MS leachate at 0.00023--0.0052,0.043--3.89,0.026-0.171,and 1.43-8.52 mg·L-1,respectively)also exceed the limits(Class IV-V)of the Chinese Standard for Groundwater Quality(GB/T 14848-2017).Based on the above results,it is suggested that without any pretreatment for reducing harmful pollutants MS should not be allowed to be applied for soil remediation or conditioning directly into farmlands in order to ensure soil health,food safety and environmental quality.
