Synthesis of α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposite for effective removal of phosphate from water

Abstract A novel α‐manganese dioxide/β‐dicalcium silicate (α‐MnO 2 /β‐C 2 S) nanocomposite was synthesized for adsorption of phosphate ions from water to inhibit eutrophication. The adsorption rate constants ( k 2 ) of α‐MnO 2 /β‐C 2 S nanocomposite are higher than those of bare α‐MnO 2 and β‐C 2 S revealing an increased adsorption rate in composite materials. The higher adsorption capacity of nanocomposites results from relatively larger pores. The phosphate sorption process obeys the pseudo‐second‐order kinetic model well and is likely governed by chemisorption. The equilibrium removal capacities of α‐MnO 2 , β‐C 2 S, and α‐MnO 2 /β‐C 2 S nanocomposite were found to be 25, 34.48, and 52.63 mg/g, respectively, which are very close to experimental values. Adsorption of PO 4 3− onto adsorbents could be favorably described by the Langmuir model. D‐R isotherm model fitting showed physical adsorption by β‐C 2 S and α‐MnO 2 /β‐C 2 S nanocomposites and chemisorption on α‐MnO 2 . The maximum adsorption capacities ( q m ) of the adsorbents calculated from the Langmuir model were 28.58, 44.03, and 63.65 mg/g α‐MnO 2 , β‐C 2 S, and α‐MnO 2 /β‐C 2 S nanocomposites respectively. The thermodynamic parameters showed that the adsorption process occurs spontaneously with an exothermic nature and a decrease in randomness. The presence of coexisting Cl − anions decreases the adsorption capacity.