The hexavalent chromium in water is extremely toxic to most living organisms and can cause many diseases. In this work, we developed Polypyrrole (PPy), Polypyrrole/graphene oxide (PPy/ GO) nanocomposite, and Polypyrrole/graphene oxide/zerovalent iron nanoparticles (PPy/GO/n-ZVI) nanocomposite for adsorption of Cr (VI) from water. PPy/GO nanocomposite showed the highest Cr (VI) removal capacity for 10 % (weight) loading of GO. PPy/GO/n-ZVI nanocomposite showed the highest Cr (VI) adsorption capacity for 50 % iron nanoparticle loading. Chemical kinetics data showed that Cr (VI) adsorption occurred with pseudo-second-order. The maximum adsorption capacity (q max ) was found to be 64.29 mg/g, 129.09 mg/g, and 171.04 mg/g on PPy, PPy/GO nanocomposite, and PPy/GO/n-ZVI nanocomposite respectively. The thermodynamic study showed a positive value of ΔS, and a negative value of ΔG indicated rise in the disorder at the adsorbate-adsorbent interface and spontaneous nature of Cr (VI) adsorption. ΔH was close to 21 kJ/mole indicating adsorption process occurred via physisorption. The recycling of the adsorbent was carried out by washing with sodium hydroxide and Cr (VI) removal efficiency decreased by around twenty % in the fifth cycle. The present study suggests that the PPy/GO/n-ZVI nanocomposite is an environment-friendly magnetic material and provides a simple, low-cost strategy for the adsorption of Cr (VI) from wastewater.
A novel α‐manganese dioxide/β‐dicalcium silicate (α‐MnO2/β‐C2S) nanocomposite was synthesized for adsorption of phosphate ions from water to inhibit eutrophication. The adsorption rate constants (k2) of α‐MnO2/β‐C2S nanocomposite are higher than the bare α‐MnO2 and β‐C2S 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 capacity of α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposite was found to be 25 mg/g, 34.48 mg/g, and 52.63 mg/g which are very close to experimental values. Adsorption of the PO43− onto adsorbents could be favorably described by the Langmuir model. D‐R isotherm model fitting showed physical adsorption by β‐C2S and α‐MnO2/β‐C2S nanocomposites and chemisorption on α‐MnO2. The maximum adsorption capacity () of the adsorbents calculated from the Langmuir model were 28.58 mg/g, 44.03 mg/g, and 63.65 mg/g α‐MnO2, β‐C2S, and α‐MnO2/β‐C2S nanocomposites respectively. Thermodynamic parameter showed adsorption process occurs spontaneously in the nature exothermic nature decrease in randomness. The presence of coexisting Cl− anions decrease adsorption capacity.This article is protected by copyright. All rights reserved
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