Arsenate removal from aqueous solutions using micellar-enhanced ultrafiltration.

In this study, arsenate (As-V) removal using micellar enhanced ultrafiltration (MEUF) modified by cationic surfactants was studied by a dead-end polyacrylonitrile (PAN) membrane apparatus. The UF membrane has been produced by a phase inversion process. The prepared membrane was characterized and analyzed for morphology and membrane properties. The influence of operating parameters such as initial concentrations of As-V, surfactants, pH, membrane thickness, and co-existing anions on the removal of As-V, surfactant rejection, and permeate flux have been studied. The experimental results show that from the two different cationic surfactants used the CPC (cetyl-pyridinium chloride) efficiency (91.7%) was higher than that of HTAB (hexadecyltrimethyl-ammonium bromide) (83.7%). The highest As-V removal was 100%, and was achieved using initial feed concentrations of 100-1000 µg/L, at pH 7 with a membrane thickness of 150 µm in a dead-end filtration system. This efficiency for As-V removal was similar to that obtained using a cross-flow system. Nevertheless, this flux reduction was less than the reduction achieved in the dead-end filtration process. The PAN fabricated membrane in comparison to the RO and NF processes selectively removed the arsenic and the anions, in the water taken from the well, and had no substantial effect on the cations.

Application of modified electrospun nanofiber membranes with α-Fe2O3 nanoparticles in arsenate removal from aqueous media.

In the present study, electrospun nanofiber membranes (ENMs) of polyacrylonitrile (PAN) were modified by dispersing α-Fe2O3 nanoparticles, synthesized using a thermal solvent process, in a PAN solution. The morphology and physiochemical properties of the prepared ENMs and the α-Fe2O3 were characterized using FESEM, EDX, BET, XRD, FTIR, porosity, and contact angle measurement. XPS was used to investigate the interaction of ENM with arsenate (As(V)) during the adsorption. Moreover, the effect of pH, the equilibrium isotherm, and the kinetics were investigated in batch experiments. The Langmuir isotherm best correlated the experimental results, indicating monolayer adsorption on ENMs, and the kinetics was best fitted, R2 > 0.99, by the pseudo-second-order model. In addition, the effects of certain conditions on the filtration performance were examined, such as feed concentration and transmembrane pressure (TMP). By passing sodium hydroxide (0.1 M) for 20 min, the membrane was regenerated. The increase in TMP, along with the presence of co-ions including chloride, nitrate, and sulfate, had negative impacts on the removal of As(V). The results show that the modified ENMs with α-Fe2O3 nanoparticles are applicable for As(V) ion removal and possibly for eliminating other heavy metals from aqueous media.

Carboxymethyl cellulose production from sugarcane bagasse with steam explosion pulping: Experimental, modeling, and optimization.

The sugarcane bagasse was used for producing carboxymethyl cellulose (CMC) and obtaining high-molecular-mass hemicellulose as co-product. To this end, the steam explosion process was employed. It was found that the optimum operating conditions are the temperature of 187.15°C, NaOH/bagasse ratio of 39% (w/w), and retention time (RT) of 10min. Next, the obtained cellulose in the optimized condition was extracted and purified, and it was subsequently converted to CMC according to Williamson etherification technique. This paper also employed response surface methodology (RSM) to model effective factors against a degree of substitution (DS). Based on it, the optimum values of independent variables are the NaOH concentration of 28.4%, MCA mass of 1.14gram, temperature of 57.85°C, and reaction time of 4.01h which the CMC had the DS of 1.085, the yield of 181.302%, purity of 71.6%, and crystallinity of 30.1% with low viscosity. Samples comparatively studied by FT-IR, TGA and XRD.

High-flux ultrafiltration membrane based on electrospun polyacrylonitrile nanofibrous scaffolds for arsenate removal from aqueous solutions.

Arsenic contamination in drinking water is a serious problem worldwide. In this study, to remove arsenate from contaminated water, a new thin-film composite (TFC) membrane was fabricated and tested. This membrane was composed of an electrospun nanofibrous scaffold, a polyethylene terephthalate (PET) substrate as support, and a polyacrylonitrile (PAN) coating layer. To effectively reject arsenate ions, cetylpyridinium chloride (CPC) pretreatment was used. For evaluating the performance of TFC membrane, its flux and contaminant rejection were compared to a conventional ultrafiltration (UF) membrane. Due to high porosity, the TFC membrane showed a flux, which was 172-520% higher than the UF membrane. In addition, The TFC membrane was 1.1-1.3 times more efficient in rejecting arsenate ions than the UF membrane.