The flocculation process of ferrous sulfate in wastewater is the process of electroneutralization and adsorption of soluble pollutants into sludge after hydrolysis. The coagulation of ferrous sulfate can be divided into two parts, one is used for chemical flocculation (such as adsorption bridging, hydride generation alum), the other is used for physical flocculation (such as double electric layer compression, colloidal electric neutralization). When the hydrolysis reaction of ferrous sulfate causes the colloidal substance to produce different potential ions in water, it will lose stability and generate bonding reaction, which makes the small particles of colloidal pollutants become colloidal particles and alum flower precipitation.
Adding ferrous sulfate to the wastewater for electrolysis produces a large number of positively charged ferrous ions, which neutralizes more and more charges on the surface of the pollutant colloid, and the ions exchange with positively and negatively charged colloidal particles in the water. Finally, the main attractive colloidal particles form flocculation and sedimentation.
During the solidification process of ferric sulfate in wastewater, a part of divalent ferrous ions are hydrolyzed and oxidized to trivalent iron ions. Under the action of Brownian motion and agitation, it adsorbs and cleans the residual phosphate and other pollutants in the water and forms a huge alum flower deposit. The density of oxyhydrogen alum formed by the reaction of Fe3 + with various metal salts is large, the settling speed is fast, the density of precipitated sludge is large, and the treatment is convenient.
Flocculation effect of ferrous sulfate
Ferrous sulfate is one of many inorganic chemical coagulants. It is widely used in the treatment of printing and dyeing wastewater, papermaking wastewater, electroplating wastewater and other wastewater with high chroma and total phosphorus, due to the good effect of ferrous sulfate decolorization, phosphorus removal and coagulation. Moreover, the by-product cost of titanium dioxide is very low (about 200 / ton). At present, with the improvement of wastewater discharge standard, ferrous sulfate as Fenton reagent has been widely used in papermaking wastewater treatment.
In addition to its good color removal effect, ferrous sulfate coagulation has a good treatment effect on the flocculation principle of ferrous sulfate in wastewater such as hexavalent chromium and zinc. The application of dry ferrous sulfate can completely replace the biochemical Fenton process in the treatment of COD in pharmaceutical wastewater. Because its pH value adaptability range is higher than the ordinary ferrous sulfate heptahydrate.
Ferrous sulfate used in wastewater treatment
With the increasingly serious environmental pollution, people pay more and more attention to the environmental pollution of industrial wastewater. Therefore, the wastewater needs to be treated before discharge, and then there are many ways to treat the wastewater. The most economical and effective way is to use chemical coagulation treatment, adding coagulant in the wastewater to achieve the purpose of removing pollutants.
The waste water is chemically treated. Taking ferrous sulfate as an example, ferrous sulfate is widely used in wastewater treatment because it is a by-product of titanium dioxide with good water treatment effect and low cost. The function of ferrous sulfate is a kind of colloidal particle, organic matter, microorganism in the water, which makes the suspended matter of wastewater have strong adsorption bridging and electric neutralization, make them settle in the water, and eliminate its influence on the water.