Effects of phosphate, silicate, humic acid, and calcium on the release of As(V) co-precipitated with Fe(III) and Fe(II) during aging.

The effects of phosphate (P), silicate (Si), humic acid (HA), and calcium (Ca) on the release of As(V) co-precipitated with Fe(III) and Fe(II) during aging were investigated. As(V) in synthetic groundwater could be efficiently removed by both Fe(III) and Fe(II) processes. The addition of P remarkably decreased As(V) removal efficiency while no obvious release of As(V) during aging was observed. Si and HA reduced As(V) removal to a less extent than P but caused notable As(V) release during aging. FTIR spectra and particle size of the precipitates before and after aging indicated that As(V) release in the presence of Si was due to the serious structural transformation and particle aggregation of the precipitates during aging. While for HA, As(V) release was caused by sorption of HA on the precipitates and dissolution of the precipitates by HA. The addition of Ca partially counteracted the adverse impacts of P, Si, and HA and promoted As(V) removal efficiency but had limited inhibitory effect on As(V) release as it induced more serious particle aggregation during aging. The results demonstrated that the release of As(V) caused by Si and HA should be considered when using Fe coagulation for in-situ treatment of As(V) contaminated groundwater.

Removal of pharmaceuticals and personal care products (PPCPs) and environmental estrogens (EEs) from water using positively charged hollow fiber nanofiltration membrane.

Nanofiltration (NF) membranes show great potential for advanced water treatment, especially for trace organic pollutant removal. The removal efficiency of pharmaceuticals and personal care products (PPCPs) and environmental estrogenic hormones (EEHs) by positively charged hollow fiber NF membranes (PEI-NF) were evaluated. The separation properties were evaluated by changing the operating pressure, temperature, ionic strength, and cation species. A relationship between the physicochemical characteristics of the pharmaceuticals and the NF membrane retention behavior was established. The results showed that the rejection rates of the PEI-NF membrane for the selected PPCPs and EEHs ranged from 81 to ~ 91.26%. For positively (negatively) charged pharmaceutical molecules, the electrostatic repulsion (attraction) effect and steric hindrance were the dominant rejection mechanisms of the PEI-NF membrane. For neutral pharmaceutical molecules, in addition to the size sieving effect, the hydration-induced size increase of hydrophilic substances improved the rejection rates. Both the molecular structure and diffusion coefficient of pharmaceutical molecules influenced their rejection by the PEI-NF membrane to a certain extent. Moreover, the PEI-NF membrane showed a high removal effect for PPCPs and EEHs in water samples from actual tap water plants.

In-situ self-assembly of robust Fe (III)-carboxyl functionalized polyacrylonitrile polymeric bead catalyst for efficient photo-Fenton oxidation of p-nitrophenol.

From the view of channel confinement and functional site capture, we develop an in-situ self-assembly strategy to fabricate the carboxyl functionalized Fe-HPAN bead catalyst with highly stable and uniformly dispersed metallic sites for efficient photo-Fenton oxidation of p-nitrophenol (p-NP). BET and FTIR analysis reveal that numerous carboxyl groups and mesopores exist in Fe-HPAN beads, which acts to capture and immobilize iron ions. Catalytic results show that the degradation rate and TOC removal for p-NP were up to 99.78 and 91.68% under the optimal condition. Even at near neutral pH, the degradation rate almost keep the same and the TOC removal can still reach 73.05%. Due to the autocatalytic cycle of FeIII/FeII, the apparent rate constant of Fe-HPAN (0.2247 min-1) was 5.4 times as high as unmodified Fe-PAN (0.0415 min-1) in the presence of H2O2 and visible light irradiation, which was 2-3 orders of magnitude larger than that of other reaction systems. More importantly, Fe-HPAN bead catalyst exhibited little loss of activity even after 20 cycles of re-utilization. The possible degradation pathway of p-NP was also proposed based on GC/MS analysis. The present work may provide a new perspective for the use of synthetic polymer to prepare low-cost, efficient and robust photo-Fenton oxidation catalysts.

Typical pharmaceutical molecule removal behavior from water by positively and negatively charged composite hollow fiber nanofiltration membranes.

The rejection behaviors of two different charged composite hollow fiber nanofiltration (NF) membranes for six pharmaceutical molecules, primidone, carbamazepine, sulfamethoxazole, atenolol, sulfadimidine and norfloxacin, were characterized in this study. The saturation adsorption behaviors of the different pharmaceutical molecules on each membrane surface were studied and found to be related to the molecular weight, charge and hydrophilicity of the pharmaceutical molecules. After the pharmaceutical molecules reached adsorption equilibrium, the rejection rates of different NF membranes were characterized. The rejection rates of primidone, carbamazepine, sulfamethoxazole, atenolol, sulfadimidine and norfloxacin by the PEI-NF membrane were 85.6%, 91.8%, 79.9%, 98.1%, 93.3%, and 97.1%, respectively. Meanwhile, the rejection rates of the pharmaceutical molecules by the PIP-NF membrane were 82.2%, 85.4%, 91.5%, 79.1%, 87% and 93.3%, respectively. The influence of feed concentration, operation pressure, temperature, pH and ionic strength on the rejection behaviors of the different charged NF membranes were also studied.

Enhanced submerged membrane bioreactor combined with biosurfactant rhamnolipids: performance for frying oil degradation and membrane fouling reduction.

In this study, a novel submerged membrane bioreactor (SMBR) combined with rhamnolipids was developed to treat frying oil wastewater and control the problem of membrane fouling. To validate the feasibility of this new design, a hybrid SMBR with additional rhamnolipids (RSMBR) and a controlled SMBR (CSMBR) were run in parallel. Results demonstrated that RSMBR not only held high removal efficiency of oil up to 90% at short hydraulic time, but also exhibited 10 times higher membrane permeability in comparison to CSMBR. The presence of rhamnolipids greatly enhanced the contact and reaction between the microorganism and oil molecules. The great improvement in membrane filterability was associated with an increase in hydrophobicity of flocs as well as the increase of particle size from 53.06 to 145.54 µm. The oil strongly adhered to the surface of flocs by rhamnolipids, and consequently prevented larger oil droplets directly depositing on the membrane surface.