Facile synthesis of composite polyferric magnesium-silicate-sulfate coagulant with enhanced performance in water and wastewater

The coagulation process is a widely applied technology in water and wastewater treatment.Novel composite polyferric mag-nesium-silicate-sulfate(PFMS)coagulants were synthesized using Na_(2)SiO_(3)·9H_(2)O,Fe_(2)(SO_(4))_(3),and MgSO_(4) as raw materials in this paper.The effects of aging time,Fe:Si:Mg,and OH:M molar ratios(M represents the metal ions)on the coagulation performance of the as-pre-pared PFMS were systematically investigated to obtain optimum coagulants.The results showed that PFMS coagulant exhibited good co-agulation properties in the treatment of simulated humic acid-kaolin surface water and reactive dye wastewater.When the molar ratio was controlled at Fe:Si:Mg=2:2:1 and OH:M=0.32,the obtained PFMS presented excellent stability and a high coagulation efficiency.The removal efficiency of ultraviolet UV254 was 99.81%,and the residual turbidity of the surface water reached 0.56 NTU at a dosage of 30 mg·L^(-1).After standing the coagulant for 120 d in the laboratory,the removal efficiency of UV254 and residual turbidity of the surface wa-ter were 88.12%and 0.68 NTU,respectively,which accord with the surface water treatment requirements.In addition,the coagulation performance in the treatment of reactive dye wastewater was greatly improved by combining the advantages of magnesium and iron salts.Compared with polyferric silicate-sulfate(PFS)and polymagnesium silicate-sulfate(PMS),the PFMS coagulant played a better decolor-ization role within the pH range of 7-13.

Efficient removal of algae and turbidity from water by a composite coagulant composed of a cationic starch and attapulgite

Algae and suspended colloidal particles produced high turbidity in water,weakened water purification,and threatened the safety of the water supply.In this study,a series of composite coagulants(atp-st-CTA)composed of a cationic starch(st-CTA)and attapulgite(ATP)with different fed mass ratios were fabricated by a simple method to coagulate kaolin suspension with initial turbidity of 80.0 NTU and Chlorella suspension with 0.25 mg/L of chlorophyll a(chla),respectively.Fourier transform infrared spectroscopy and scanning electron microscopy investigated the structural characteristics of atp-st-CTA.The maximum turbidity and chla removal rates of atp-st-CTA were 92.2%and 100.0%,respectively,at natural pH conditions.The effects of the fed mass ratio of st-CTA to ATP in the composites,dose,pH,and coexisting humic acid on the coagulation performance of atp-st-CTA were comprehensively investigated.Based on the apparent coagulation behaviors,the zeta potentials of the supernatants after coagulation,and the flocs properties,the coagulation mechanisms of atp-st-CTA were discussed in detail.The complete charge neutralization due to st-CTA and the enhanced sedimentation by ATP synergistically removed turbidity and algae from the water efficiently.In short,atp-st-CTA as a talented material has a notable prospect in applications of water treatment owing to its advantages of environmental friendliness,low cost,and high efficiency.