Chromium(VI) is one of the most toxic contaminants in the environment, even at low concentration. The conventional chemical precipitation process for Cr(VI) wastewater treatment becomes less effective at low Cr(VI) concentration. By a two-step solvent–nonsolvent method, tricaprylmethylammonium chloride (Aliquat 336) can be immobilized onto the surface of porous Amberlite XAD resin with good stability, giving Aliquat 336-modified resins (AMRs). Furthermore, the exposure of the cationic ammonium functional group facilitates the adsorption and stripping efficiency of Cr(VI). The amount of immobilized tricaprylmethylammonium chloride was 2.0 mmol/g of resin. A kinetic study showed that the adsorption of Cr(VI) was under film-diffusion control followed by intraparticle-diffusion control. The Cr(VI) adsorption capacity was as high as 1.37 mmol/g. More than 99% of the adsorbed Cr(VI) could be stripped during regeneration. For stability and reusability, the AMRs maintaine da high level of Cr(VI) adsorption even after four cycles of adsorption/stripping. The experimental results for actual wastewater demonstrated that the AMRs can be used effectively for the treatment of trace Cr(VI)-containing wastewater.

The structural characteristics of membrane support directly affect the performance of carrier facilitated transport membrane. A highly porous PolyHIPE impregnated with Aliquat 336 is proposed for Cr(VI) separation. PolyHIPE consisting of poly(styrene-co-2-ethylhexyl acrylate) copolymer crosslinked with divinylbenzene has the pore structure characteristic of large pore spaces interconnected with small window throats. The unique pore structure provides the membrane with high flux and stability. The experimental results indicate that the effective diffusion coefficient D* of Cr(VI) through Aliquat 336/PolyHIPE membrane is as high as 1.75 × 10−11 m2 s−1. Transport study shows that the diffusion of Cr(VI) through Aliquat 336/PolyHIPE membrane can be attributed to the jumping transport mechanism. The hydraulic stability experiment shows that the membrane is quite stable, with recovery rates remaining at 95%, even after 10 consecutive cycles of operation. The separation study demonstrates the potential application of this new type of membrane for Cr(VI) recovery.

Electrically conductive polymer composites (CPCs) consisting of dispersed conductive filler in a polymer matrix continue to attract increasing academic and industrial research. A facile strategy to synthesize an Ag/rGO/epoxy conductive composite by a one-pot fabrication process is proposed. The effects of the preparation parameters of the one-pot approach on the conductivity, structure, and chemical composition of Ag/rGO composite are investigated, and the correlation between the preparation parameters and the conductivity of Ag/rGO is established. In this study, Ag/rGO is prepared by using a solution oxidation–reduction method with green reductant Vitamin C. The Taguchi method and response surface methodology are used to evaluate the optimum preparation parameters. The rank of control factors for conductivity follows the order [Vitamin C] > reaction time > [AgNO3]. The optimum electrical conductivity of Ag/rGO is 123.00 S/cm with the optima preparation parameters [Vitamin C] = 2.0 g/L, [AgNO3] = 0.1 g/L, and reaction time = 6 h. In a one-pot process, the amount of available Vitamin C for the reduction of GO is an important factor. Experimental results indicate that m Vitamin GO/m GO ≥ 1.0 is required to ensure sufficient reduction of GO. The uniform Ag particle size distribution is crucial to obtain higher conductivity. The Ag/rGO/epoxy composite can be prepared by one-step in-situ reduction. Experimental results show that Vitamin C can reduce GO and Ag+ to rGO and Ag particles during polymerization of epoxy. Conductive polymer composite with conductivity as high as 17.09 S/cm can be prepared.

is one of the most important elements that are widely used in electronic devices. The development of Ga recovery technology is an important issue for resource recycling. In this study, di-(2-ethylhexyl)phosphoric acid (D2EHPA)modified XAD-4 resin (DMR) is prepared by the solvent-nonsolvent method. The evolution of pore characteristics demonstrates that the solvent-nonsolvent treatment is advantageous for the immobilization of D2EHPA in XAD-4 resin. The adsorption isotherm of Ga(III) can be described by the Langmuir isotherm model. The Ga(III) adsorption kinetics follows the pseudo-second-order model. The immobilized D2EHPA shows good stability. The reusability study indicates that DMR can maintain the performance after three cycles of adsorption and stripping. The results for the treatment of a practical leaching solution from GaN/Al 2 O 3 wafer further demonstrate that DMR can be applied effectively for Ga(III) recovery.