In this study, attapulgite (AT) and graphene oxide (GO) nanosheets were grafted together via a silane coupling agent to synthesize attapulgite−graphene oxide (AT−GO) composites and apply them to remove the emulsified oil from the oily wastewater. The structure and morphology of the AT−GO composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, zeta potential measurements, and transmission electron microscopy. The amphiphilicity of the AT−GO composites was evaluated by visual observation of their distribution in the oil−water mixture. The results showed that the AT−GO composites have been successively prepared and have good amphiphilic and interfacial activity. The effects of the pH, demulsifier dosage, temperature, and the mass ratio of AT and GO (R A/G ) in the composites on the demulsification performance of AT−GO were studied. It was found that the demulsification process could be completed efficiently and quickly at room temperature. Under optimal demulsification conditions, the demulsification efficiency is above 95%. The demulsification mechanism was studied and discussed. It is believed that the interaction behavior between the AT−GO material and the emulsified molecules of asphaltenes is a key for the demulsification. Once the nanoparticles are combined with the emulsified molecules, the external stirring, vibration, and other mechanical actions provide them enough kinetic energy to destroy the protective film at the oil/water interface and then promote the merging of dispersed oil droplets to realize the oil−water separation.
The discharge of yttrium containing wastewater is a potential risk to human health. Although biosorption is a promising method to remove yttrium from wastewater, whereas the application of it is limited due to the lack of efficient biosorbents. In this study, the removal of yttrium from wastewater using Serratia marcescens as a biosorbent was conducted. The effects of six parameters including pH (2–5.5), initial yttrium concentration (10–110 mg/L), biosorbent dosage (0.1–0.5 g/L), biosorption time (10–700 min), stirring speed (50–300 rpm) and temperature (20–60 °C) were evaluated. The main parameters were optimized using response surface methodology. The results showed that the adsorption capacity reached 123.65 mg/g at the optimized conditions. The biosorption mechanism was revealed based on a combined analysis using field emission transmission electron microscope-energy dispersion spectrum, Fourier transform infrared spectrophotometer, and X-ray photoelectron spectroscopy. These results revealed that the hydroxyl, carboxyl, and amino groups were the adsorption functional groups for yttrium ions. Biosorption of yttrium by S. marcescens is under the combination of ion exchange, electrostatic attraction and complexation. These findings indicated that S. marcescens can be used as an efficient biosorbent to remove yttrium from wastewater. In addition, its adsorption capacity can be further improved by the enhancement of adsorption functional groups on the surface through chemical modification.
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