Talc is a magnesia silicate with a special layered structure, which has stable chemical properties, a unique pore structure and a large specific surface area. Powdered talc has oleophilic hydrophobicity and excellent adsorption, and has abundant reserves and low cost. In recent years, talc has been successfully applied to the field of sewage treatment, and it has been used as a coagulant, a coagulant, a filter aid, Related research on adsorbents and oil absorbing agents. The main component of talc is an aqueous magnesia silicate. Its structure is a 2:1 type monoclinic system consisting of two layers of silicate tetrahedron with a layer of brucite octahedron. The chemical formula is Mg3(Si4O10) (OH). 2, its composition is MgO 31.72%, SiO2 63.52%, H2O 4.76%. .
At present, the methods for treating sewage at home and abroad mainly include physical methods, chemical methods and biological treatment methods. Among them, the adsorption method is widely used because of simple process, low cost and good effluent quality. Other methods have complicated operation and operating costs. High or secondary pollution problems. At present, the most used adsorbent is activated carbon, but its price is expensive and the purification effect is relatively slow, which limits its wide application. Talc is a kind of natural clay mineral. Talc is a kind of sorbent material which is separated by air, broken, ground, washed and dried. It is rich in raw materials and low in price. It is a good adsorbent material. Therefore, domestic and foreign scholars have been using talc to treat water pollution more and more.
1. Handling papermaking wastewater
The papermaking wastewater mainly comes from the pulping and papermaking production process in the paper industry. The main components are lignin, cellulose, volatile organic acids, etc., which have high pollutant concentration, large discharge, difficult to degrade, and poor biodegradability. It is one of the industrial wastewaters that are difficult to handle. In recent years, the application research of talc powder as a coagulant, coagulant and filter aid to treat papermaking wastewater has made gratifying progress.
1.1 As a coagulant to treat papermaking wastewater
Under the optimal coagulation conditions, the amount of talc mixed with polyferric sulfate (PFS), polyaluminum chloride (PAC) and polyaluminum ferric sulfate (PAFS) is 0.8-1.0, 1.2, 0.4-0.5g/ At L, the removal rate of CODcr increased by 3.0%, 4.0% and 2.5%, respectively, and the removal rate of suspended solids (SS) increased by 27.1%, 29.4% and 26.5%, respectively. The experimental results show that the ultrafine talc powder (SFT, average particle size 12μm) is effective as a coagulant and PAC or PFS coagulation treatment of papermaking wastewater. When the SFT dosage is 1mg/L, the coagulation effect is better. Polyacrylamide (PAM), the cost is reduced by about 23%. One of the reasons why talc is used as a coagulant is that it has more surface hydroxyl groups. These reactive functional groups can participate in surface proton migration and surface complexation reaction to adsorb pollutants.
1.2 As a filter aid for the treatment of papermaking wastewater
Membrane Bioreactor (MBR) is a new type of water treatment technology that combines a membrane separation unit with a biological treatment unit. It has the characteristics of simple operation and strong adaptability, and has been used to treat papermaking wastewater [11], but the problem of membrane fouling needs to be solved urgently. The papermaking wastewater is treated by adding talc to the MBR. The results showed that when the dosage of talc powder was 1.2g/L (screened by 0.1mm pore size sieve), the CODcr removal rate could reach more than 90%, and the addition of talc filter aid reduced the membrane pollution resistance by 68.5%. The filter cake resistance decreased by 91.1%, which slowed the membrane fouling and prolonged the service life of the membrane. Because the filter aid talcum powder has strong adsorption, the sludge floc is more likely to aggregate, the viscosity is also reduced, and the membrane fouling resistance is reduced. The development of the new cheap talc filter aid is the application of talc. New Direction.
Talc, a non-metallic mineral that has been widely used and has significant social and economic benefits, is increasingly showing its feasibility in environmental protection. The advantages and disadvantages of talc in various wastewater treatments are compared below, as shown in Table 1. Although talcum powder has some shortcomings in wastewater treatment, talc powder has great application prospects in water treatment process due to its large reserves, wide distribution, low cost and low pollution.
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