Efficient removal of Cs(I) from water using a novel Prussian blue and graphene oxide modified PVDF membrane: Preparation, characterization, and mechanism.

The Prussian blue (PB) blending membranes are promising candidates for the removal of trace radionuclide Cs+. Constructing a membrane with high flux and selectivity are challenging in its practical application. Here, a novel polyvinylidene fluoride (PVDF)-PB-graphene oxide (GO) modified membrane was fabricated via phase inversion for trace radionuclide cesium (137Cs) removal from water. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze chemical composition and morphology of the membrane, and the properties in terms of water flux and Cs+ removal were studied under different PB dosage, pH and co-existing ions conditions. It was observed that the addition of GO improved the dispersion of PB, and the PVDF-PB-GO membrane presented the highest Cs+ removal efficiency (99.6 %) and water flux (1638.2 LMH/bar) at pH = 7 with 0.1 wt% GO and 5 wt% PB. In addition, Langmuir and pseudo-second-order kinetics models fitted well for Cs+ adsorption by the PVDF-PB-GO membrane, illustrating that the Cs+ was removed via chemical adsorption dominated by Fe(CN)64- defect sites of PB and the oxygen groups of GO. Furthermore, the membrane showed a significant selectivity and reusability towards trace radioactive cesium, even in the presence of excess co-existing ions and in real water, which strongly verified that the modified membrane had application potential.

Value-added utilization of paper sludge: Preparing activated carbon for efficient adsorption of Cr(VI) and further hydrogenation of furfural.

After normal alkali treatment process, the industrial Cr(VI) containing wastewater still contains a ppm level of Cr(VI) ions which should be further purified before discharging. In this study, the Cr(VI)-containing wastewater has been efficiently treated by the porous paper sludge-based activated carbon (psAC) with an excellent specific surface area and rich oxygen functional groups. The batch experimental results showed that under acidic conditions, pH has little effect on the Cr(VI) removal. The kinetic and isotherms studies showed that the Elovich and Freundlich model could describe the adsorption process well and the maximum adsorption capacity of psAC was 54.04 mg/g. The thermodynamic studies indicated that the reaction process was endothermic and spontaneous. Adsorption enthalpy was 17.37 kJ/mol, showing that the chemisorption process was a hydrogen bonding-controlled that has been also verified by some analytical techniques. Lastly, this study also provided an idea for reutilization of waster Cr(VI)-contained psAC in furfural hydrogenation.