Synthesis of TiO2/ZnO electrospun nanofibers coated-sewage sludge carbon for adsorption of Ni(II), Cu(II), and COD from aqueous solutions and industrial wastewaters

The nanofibers prepared by electrospinning process have high potential for the removal of toxic matters from wastewaters. In the present study, the titanium dioxide and titanium dioxide/zinc oxide (TiO2/ZnO) nanofibers prepared by electrospinning technique were coated on the sewage sludge carbon (SSC) surface for adsorption of Ni(II), Cu(II), and COD from aqueous solutions and industrial wastewaters of Iran. The synthesized adsorbents were characterized using XRD, SEM and EDX analysis. The effect of adsorbent type, pH, adsorbent dosage, contact time and initial concentrations of Ni(II), Cu(II) and COD on the adsorption capacity of synthesized SSC/TiO2 and SSC/TiO2/ZnO nanofibrous adsorbents was investigated. The optimum pH values of 5, 6 and 7, adsorbent dosage of 0.5 gL−1, and equilibrium time of 30 min were obtained for maximum adsorption of Ni(II), Cu(II) and COD using SSC/TiO2/ZnO nanofibrous adsorbent. The kinetic and isotherm data were best described using pseudo-second-order kinetic and Redlich-Peterson isotherm models. The maximum monolayer sorption capacities of Ni(II), Cu(II) and COD were found to be 282.3 mg.g−1, 298.1 mg.g−1and 2220.3 mg.g−1, respectively using SSC/TiO2/ZnO nanofibrous adsorbent. The reusability of the nanofibers for adsorption of Ni(II), Cu(II), and COD was also examined for five runs. The simultaneous adsorption of Ni(II), Cu(II) and COD from aqueous solutions and industrial wastewater in a ternary system was also investigated. The obtained results indicated the high capability of SSC/TiO2/ZnO nanofibrous adsorbent for the removal of heavy metals and COD reduction from wastewaters.