Principle
Put some chemical agent to waste water to react with some of the dissolved substances in water, generate it is difficult to dissolve the water, thereby reducing these The content of the solubility is referred to as a chemical precipitation method of water treatment.
Water is difficult to dissolve the salt to obey the solubility, i.e., at a certain temperature, in a saturated solution containing the hard-soluble salt, the product of various ion concentrations is a constant, that is, the number of solubility . To remove some of the ions in the wastewater, it can be added to the water to generate another ion of the hard to dissolve the salt, and the product of the two ions is larger than the solubility of the difficult dissolution salt, which forms a precipitate, thereby reducing wastewater. This ion content is content. No ion can be separated from the wastewater in the wastewater, first determined to find a suitable precipitant. In general, mercury, lead, copper, zinc, hexavalent chromium, sulfur, cyanide, fluoride plasma in wastewater may be separated from wastewater by chemical precipitation.
Application
Chemical precipitation method is often used to treat wastewater containing a toxic compound such as mercury, lead, copper, zinc, hexavalent chromium, sulfur, cyanide, fluorine, arsenic. The metal ions in the wastewater can be removed by chemical precipitation in the wastewater by vaporizing hydroxide, sulfide, carbonate, halide or the like to waste water, and pose a barium salt to waste water can be used to treat industrial wastewater containing hexavalent chromium. Chromate precipitate, pose a stone into the wastewater to form a fluoride precipitate to remove fluoride in water.
Common method
Different from the precipitant used, there is a common chemical precipitation method, a sulfide precipitation method, a carbonate precipitation method, and atrium salt precipitation , Halide precipitation method, etc.
Precautions
(1) Increase the amount of precipitating agent, can improve the removal rate of ions in wastewater, but the amount of the precipitant should not be added too much, otherwise it will result in The opposite effect is generally not more than 20% to 50% of theoretical amount.
(2) When chemical precipitation is treated with industrial wastewater, the resulting precipitate generally does not form a charged colloid, so the precipitation process will become simple, and ordinary air-flow precipitation or vertical flow The precipitate is, and the residence time is shorter than the precipitation time in the wastewater or organic wastewater treatment, and it is generally determined by the small test.
(3) When used for different processing targets, the desired administration and reaction apparatus are also different. Some agents can be done, while others need to dissolve the agents and dilute into a certain concentration, and then proportionally.
(4) Some wastewater or medicament have corrosive, and the administration and reaction devices adopted should be fully considered to meet the corrosion requirements.