Oriented growth of copper & nickel-impregnated δ -MnO2 nanofilaments anchored onto sulfur-doped biochar template as hybrid adsorbents for removing phenolic compounds by adsorption-oxidation process

Abstract

In the present study, the oxidative absorption was introduced as a new technique in removing hazardous organic pollutants from water and wastewater. Hence, at first manganese dioxide nanodisks were synthesized on sulfur enriched biochar through the simple oxidation–reduction process to play the role of an efficient adsorbent. In the following, the incorporation of copper and nickel in the MnO2 structure generates strain within that structure. This leads to creating crystal defect states as well as the change of phase from γ -MnO2 to δ-MnO2 and also morphology to nanofilaments which increasing specific surface area. Scanning electron microscopy technologies and X-ray diffraction patterns were used to study the surface morphology, and Brunauer–Emmett–Teller analysis was used to determine the specific surface area of the adsorbents. Then, the efficiency of the prepared nanofilaments for removing phenolic compounds from aqueous solutions in a batch and equilibrium system was investigated. Adsorption isotherms (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo-first-order, pseudo-second-order, and Elovich) were used to explain the adsorption process. Results showed the maximum sorption capacitiy at the equilibrium time 18 h with adsorbent dosage of 1.0 mg/mL and pH=4 was obtained. Langmuir isotherm and the pseudo-second-order kinetic model have the best fitness on experimental data. The thermodynamic study of the adsorption of phenolic compounds by nanofilaments shows that this endothermic process is associated with spontaneous and irregular increases. This research shows that the designed adsorbents may be the effective, low-cost, and environmentally-friendly adsorbents to remediate phenol contaminations in the wastewater.