Polymers play an important role in water purification due to advantages such as the enhanced capacity of the treatment plant, the lowering of sludge production compared to inorganic coagulants, etc. The formation of clay/polymer complex during the coagulation-flocculation process facilitates the removal of toxic pollutants from water. Although polymers have been utilized in the coagulation-flocculation processes, there is not much information about the relationship between polymer structure and treatment performance. The use of polymers as membranes is mainly due to their flexibility, ease of handling, and cost-effectiveness compared to inorganic membranes. However, they also have some disadvantages, such as chemical attacks, membrane fouling, etc. Therefore, recent studies have focused on improving chemical resistance, antifouling properties, etc. through blending and surface modification. This chapter will review the applications of various polymers in water purification, the deficiencies of current membranes, and possible ways of improving them with novel polymer chemistry.
TopIntroduction
One of the most significant challenges of the 21st century is to provide clean water at an affordable cost. According to a 2017 report by the World Health Organization (WHO), 2.1 billion people lack access to a safe drinking water supply at home. Although much water is available on the earth, most of it is not good (pure) enough for human consumption due to the various impurities in water such as suspended solids, dissolved solids, synthetic chemicals, metal ions, nitrate, phosphate, and pathogens. Therefore, drinking water resources require appropriate treatment to remove these disease-causing agents. The treatment methods depend on the water source (surface water, underground water, etc.) and the end-use (drinking, irrigation, etc.). The most common water treatment steps to provide safe drinking water involve coagulation, flocculation, sedimentation, filtration, disinfection, fluoridation, and pH correction.
Polymers play an important role in coagulation, flocculation, and filtration. (Kawamura, 1976; Geise et al., 2010) The formation of clay/polymer complex during the coagulation/flocculation process facilitates the removal of toxic pollutants from water. The coagulation step is followed by a separation step of sedimentation or flotation with a final polishing by filtration. The use of polymer in the coagulation/flocculation process offers some advantages, such as the increased capacity of the treatment facility, the lowering of the dosage of other chemicals, and sludge production. The use of polymer in coagulation/flocculation also widens the range of water that can be treated.
Polymers are also used as membranes in reverse osmosis, nanofiltration, ultrafiltration, and microfiltration processes. (Geise et al., 2010) Membranes made from polymeric materials are cheaper than those obtained from inorganic materials. (Ng et al., 2013) Polymeric membranes can also be used to achieve high water production capacity. (Giwa et al., 2019) These membranes are easy to handle. These can also be arranged in different configurations for optimum performance. (Le & Nunes, 2016) This chapter will review the applications of various polymers in water purification, the deficiencies of current membranes, and possible ways of resolving them with novel polymer chemistry.