As a reductant, calcium sulfide is very effective in the remediation of heavy metal contaminated soils and groundwater, and is more stable and durable than other reductants, and is safe for storage and use. It is a non-toxic reagent to oxidize calcium sulphate under aerobic conditions. The areas of use include:
* sewage treatment (electroplating wastewater, mining wastewater and comprehensive chemical waste water).
* soil remediation (chromite slag site, heavy metal unreasonable discharge of contaminated sites, etc.)
* gas control (coal and oil combustion at power plants and factories, waste incineration, ore smelting of non-ferrous metals, etc.).
Advantages are prominent:
1. For heavy metal ions with high reactivity, the solubility of metal sulfides in the range of pH is very low.
2, without pretreatment, it is necessary to break and precipitate heavy metal ions that are easily chelated or complexed.
3, better precipitation and dehydration of metal precipitation, making sludge more compact and easy to filter.
4, the dissolved calcium ion can form a coagulant.
Beauty degree B e... ... Twenty-nine
The density is g/ml...... One point two five
The quality score is%... Eighteen point one
Color......... Transparent gem red
The calcium sulfide was first used to deal with copper and nickel in the mining wastewater. Later, the Irkutsk Institute of heavy metals and rare metal smelting and research laboratory applied it to the treatment of electroplating wastewater, and achieved good results. Since the 80s of last century, calcium sulfide has become more and more popular, because the cost of reducing the form of six valent chromium (VI) into trivalent chromium insoluble is very low, and the toxicity of trivalent chromium is low, and it is precipitated from the solution and attached to the soil.
The United States Environmental Protection Agency has confirmed that calcium sulfide is suitable for chemical reduction of various toxic substances; the National Health Foundation of the United States approved the use of calcium sulfide in groundwater treatment; the United States Department of agriculture also approved a variety of applications of calcium sulfide in agriculture.
The removal efficiency of Cr (VI) in groundwater was studied by using calcium polysulfide as reducing agent. The effects of calcium sulfide dosage, solution pH, temperature, Mn (II), Fe (III), and humic acid (HA) on the effect of calcium sulfide on the treatment of Cr (VI) were investigated. The results showed that when the molar ratio of calcium sulfide and Cr (VI) changed from 1 to 1 to 5: 1, the removal rate increased from 41.03% to 100%, and the removal rate decreased by 27.16% when the solution pH value rose from 6 to 9; when the water environment temperature increased from (7 + 1) C to (27 + 1) C, the removal rate reached the required reaction time, which was shortened by 4~6 times. With Mn (II), as the concentration of Mn (II) increases (0.00~10.00 mg. L-1), the concentration of Cr (VI) is 3 times shorter than that required for the detection line. When Fe (III) is contained in the groundwater, the mass concentration of Fe is increased from 0 to 10. The removal rate increases by 9.05%. The rate was reduced from 99.31% to 90.28%. (7) the value of 2 theta in the X ray diffraction spectrum of the reaction products of calcium sulfide and six valence chromium is 18.2, 19.36, 26.67, and Cr (OH) 3, and 2 theta is 23.02. And the standard card of the single S is higher. In addition, the treatment effect of 11.36 mg / L-1 Cr (VI) contaminated groundwater showed that the removal rate of Cr (VI) reached 99.78% and the residual concentration reached GB/T 1448 - 1993, the standard of groundwater quality standard III, which indicated that the application of calcium sulfide to the remediation of actual chromium contaminated groundwater has a good application prospect. This section is selected from the influence of different factors on the Cr (VI) effect of calcium sulfide treated groundwater. Hu Yue, Jilin University, School of environment and resources.
The practice has proved that the removal of heavy metal ions, whether in sewage treatment, soil remediation, or gas control, has a great value in the use of calcium sulfide, and the effect is significant. Calcium polysulfide is cheap, cheap, effective, easy to operate and convenient to handle. It is the best choice for dealing with a large number of water bodies and soil remediation.