Engineered iron/iron oxide functionalized membranes for selenium and other toxic metal removal from power plant scrubber water

Abstract

The remediation of toxic metals from water with high concentrations of salt has been an emerging area for membrane separation. Cost-effective nanomaterials such as iron and iron oxide nanoparticles have been widely used in reductive and oxidative degradation of toxic organics. Similar procedures can be used for redox transformations of metal species (e.g. metal oxyanions to elemental metal), and/or adsorption of species on iron oxide surface. In this study, iron-functionalized membranes were developed for reduction and adsorption of selenium from coal-fired power plant scrubber water. Iron-functionalized membranes have advantages over iron suspension as the membrane prevents particle aggregation and dissolution. Both lab-scale and full-scale membranes were prepared first by coating polyvinylidene fluoride (PVDF) membranes with polyacrylic acid (PAA), followed by ion exchange of ferrous ions and subsequent reduction to zero-valent iron nanoparticles. Water permeability of membrane decreased as the percent PAA functionalization increased, and the highest ion exchange capacity (IEC) was obtained at 20% PAA with highly pH responsive pores. Although high concentrations of sulfate and chloride in scrubber water decreased the reaction rate of selenium reduction, this was shown to be overcome by integration of nanofiltration (NF) and iron-functionalized membranes, and selenium concentration below 10 μg/L was achieved.

Pore functionalized PVDF membranes with in-situ synthesized metal nanoparticles: Material characterization, and toxic organic degradation

“…In our previous work, PAA tended to form a thin layer on the top of the membrane surface and block membrane pores, when immersing membrane in the polymer solution before heat treatment [52]. To diminish the formation of the PAA top layer, the PVDF membrane was placed in a Büchner funnel, which was then connected to a Büchner flask with a tube (Fig.…”

Naphthenic acids removal from high TDS produced water by persulfate mediated iron oxide functionalized catalytic membrane, and by nanofiltration

“…Analysis of the solution after acid digestion of the Fe x O y functionalized membrane showed an iron content of 12 g/m 2 of the membrane. Iron content in the membrane matrix can be increased by repetitive ion exchange cycles, with Na and Fe as demonstrated in our earlier study [44]. For this study, only one cycle of ion exchange was performed with the PAA functionalized membrane.…”

“…The observed lower permeability for functionalized membrane can, therefore, be explained by the lower volume of pores for water to flow through. In our earlier study, an excess of PAA layer on membrane surface was observed by studying surface morphology using the depth profile using X-ray photoelectron spectroscopy [44]. The excess of PAA layer on the membrane surface is due to polymerization of residual acrylic acid on the membrane surface.…”

“…In our previous work, we reported the application of iron/iron oxide functionalized membrane for removal of selenium from scrubber water by reductive pathway [44]. Here, application of membrane-based technology for NA remediation from high TDS water was investigated.…”

Heavy metal removal from simulated wastewater using electrochemical technology: optimization of copper electrodeposition in a membraneless fluidized bed electrode

“…It is recognized to be very efficient, but regeneration of the adsorbent produces a concentrated solution that requires further treatment (Merrikhpour and Jalali 2013;Ahmad et al 2015). Processes involving membranes have also been considered for the treatment of wastewater containing heavy metals (Meeks et al 2013;Gui et al 2015). Such techniques have been demonstrated to be very efficient for the removal of ions, but the large energy demand due to the high pressure required in the process is still a challenge.…”