Method of treating alkaline sludge containing heavy metal as resources

Abstract

The invention relates to the technical field of environmental protection and discloses a method for treating alkaline sludge containing heavy metal as resources; the method comprises the following steps: first, using sulfuric acid liquor to leach valuable metals in the alkaline sludge containing heavy metal, solid-liquid separating acid leached slag and acid leached liquor containing SiO2; treating the acid leached liquor by using ultrasonic waves, adding alkaline and controlling pH value of the solution to precipitate and separate CaSO4, carrying out solid-liquid separation to obtain the liquid part and the solid part containing SiO2 and CaSO4; first using ferrous sulphate to treat the liquid part and then adding alkaline to adjust pH value of the liquid part, injecting compressed air to oxidize the liquid part to form ferrite and prepare the ferrite into additives with multiple usages. The solid part is used as additives for producing cement. The method of the invention not only features good commonality but also treats various alkaline sludge containing heavy metal; in addition, the method features easily controlled process conditions, simple equipment, easy realization of large-scale production, reduction of treatment cost, thus being a technology featuring reduction and decontamination for treating heavy-metal-containing alkaline sludge waste residue as a usable resource.

Description

technical field [0001] The invention relates to the technical field of environmental protection, in particular to a method for recycling alkaline sludge containing heavy metals. Background technique [0002] With the development of industry, the amount of sludge containing heavy metals is increasing. It mainly comes from the electroplating industry, the peaceful coexistence system, the circuit board industry, and other heavy metal-containing industries. Usually, the treatment method for heavy metal-containing sewage is to first reduce hexavalent chromium to trivalent chromium with a reducing agent, and then use alkali After neutralization, heavy metal-containing alkaline sludge is obtained and then solidified with cement before being landfilled. It mainly contains heavy metals such as chromium, iron, nickel, copper, zinc and soluble salts. Caustic soda precipitation and lime precipitation are generally used to treat electroplating wastewater containing heavy metals. With c...

AI Technical Summary

Problems solved by technology

In particular, some electroplating enterprises use lime or calcium carbide as a neutralizing agent, which produces a large amount of calcium hydroxide containing heavy metals during neutralization and precipitation treatment, which increases the total amount of electroplating sludge and reduces the content of heavy metal components. Separation one by one, the amount is too small, uneconomical

[0004] The existing electroplating sludge treatment process mainly focuses on harmless treatment, although some of them also consider resource utilization and harmless treatment. For example, ammonia recovery uses ammonia water to leach Cu, Ni, and Zn in the sludge. Iron and chromium, which are difficult to handle, remain in the solid, and the ammonia treatment process is lengthy. The ammonia leaching only separates copper, zinc, and nickel. To obtain a single metal, other separation methods are required, especially the ammonia immersion liquid-solid comparison. Large, up to 12:1, resulting in large equipment volume, increased equipment investment, and a large amount of leached slag, some accounting for more than 50% of the initial sludge, and the chromium in the slag must be treated in a harmless or resourceful manner.

Therefore, the practicability is not good enough, so it is difficult to popularize and apply

[0005] At the same time, due to the small volume and many sites of each electroplating factory, the possibility of diffusion and loss of various heavy metal pollution is very high. In addition, the raw materials and processes of each electroplating enterprise are different, and the disposal methods of electroplating sludge are different. The cost of separate treatment and comprehensive utilization is very high. Long-term stockpiling will lead to environmental pollution and waste of useful resources

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