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This study introduces the application of the Fe(III)/flue gas desulfurization gypsum (FGDG) system to remove EDTA-chelated Pb(II). Systematic experiments were conducted to explore the possibility of removing EDTA-chelated Pb(II) and the crucial factors of the removal process, as well as to determine the underlying removal mechanism. The results showed that the removal reaction was a quick process, with the removal rate exceeding 90% after 1 min. The system removed 97.35% of EDTA-chelated Pb(II), reducing its concentration from 700 mg/L to 18.81 mg/L. EDTA-chelated Pb(II) can be most effectively removed at pH 2. This system had a high removal rate from 50 mg/L to 1000 mg/L of EDTA-chelated Pb(II), particularly at 700 mg/L when the removal rate reached 97.35%. When the molar ratio of Fe(III)/Pb(II) was greater or smaller than 1:1, an inhibitory effect on removal was observed. TOC and UV–Vis analyses indicated that ferric ions replaced lead ions, resulting in the conversion of the EDTA-chelated Pb(II) to EDTA-chelated Fe(III). Surface structure, crystalline phase and elemental distribution were analyzed to explore the transformation of substances. The results indicated that FGDG coprecipitated with free lead ions to form lead sulfate. Overall, the rapid and efficient removal performance with cost-effective characteristics makes the Fe(III)/FGDG system a potentially attractive method for the removal of EDTA-chelated Pb(II)in wastewater.

Arsenic-contaminated water has significant adverse impacts on human health and ecosystems. We developed a new adsorptive membrane by modifying the porous support layer of a phase inversion formed membrane for arsenic removal. Iron oxide (Fe3O4) microspheres were immobilized in the support layer of the membrane by reverse filtration, followed by dopamine polymerization. The prepared adsorptive membrane was compared with a virgin membrane without Fe3O4 microspheres and a Fe3O4 blended membrane in terms of membrane structures and separation performance. The adsorptive membrane prepared by our new method had comparable water permeability and rejection performance with the virgin membrane without Fe3O4 microspheres, but higher rejection performance and dynamic adsorption capacity than the membrane prepared by the conventional blending method. Both static and dynamic adsorption modes were used to evaluate the adsorption performance of the membranes. Our new adsorptive membrane also had excellent regeneration performance. After three regeneration cycles, the membrane was still capable of treating more than 2 tons of As-contaminated water/m2. The adsorptive membrane of 1 m2 could treat over 7 tons of water to the drinking water standard in terms of arsenic concentration during three regeneration cycles. Therefore, our adsorptive membrane may pave a new way for arsenic removal from water and ensuring drinking water security.

In this work, we have fabricated a kind of N-doped hierarchal carbon fiber web by electrospinning hollow mesoporous carbon spheres (HMCSs) into fibrous structure. The as-synthesized carbon fiber web with novel mulberry-like morphology, thus denoted as MC-FW, possesses micro/meso/macroporous porosity, large surface area, high conductivity and multi-level structure, which are highly desired for supercapacitor electrode materials. The electrochemical measurements demonstrate that the designed MC-FW shows high capacitance (298.6 F g−1), favorable capacitance retention (71.0%) and long cycle life (97.3% capacitance retention after 5000 cycles). Notably, the capacitance of 298.6 F g−1 for MC-FW is higher than the capacitance reported so far for many hollow carbon spheres and carbon fibers, which may contribute to the synergistic effect between the merits of HMCSs (e.g. micro/meso/macroporous hierarchal structure, large surface area, high pore volume) and advantages of 1D carbon fiber (e.g. large aspect ratio and high conductivity). It is believed that this distinctive carbon fiber web may show promising prospects as advanced energy storage materials and catalyst.

The efficient and durable catalysts toward electrochemical water-splitting plays significant role in clean and renewable energy storage applications. Herein, we design the Prussian blue analogues precursor by self-assembled strategy and converted it to (Fe-Co)Se2 composite by post-selenization method. Benefiting of unique porous morphology, high electrochemically active surface area and fast electron transfer ability, the excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of (Fe-Co)Se2 catalyst were obtained. It was revealed that only require overpotentials of 251 mV to arrive a current density of 10 mA cm−2 in OER system, and 90 mV was accomplished at a current density of 10 mA cm−2 toward the HER activity, along with low Tafel slope of 47.6 and 58.7 mV dec−1 was achieved for OER and HER, respectively. The (Fe-Co)Se2 catalysts with high electrochemical activity at the same time long-time durability may encourage more practical catalytic applications for renewable energy technologies.

The present study aims to verify the feasibility of directly reusing the flue gas desulphurization (FGD) gypsum generated from coal-fired power plants to adsorptively remove Pb(II) and Cd(II) from wastewater. The Toxicity Characteristic Leaching Procedure (TCLP) test was conducted to evaluate the leachability of toxic heavy metals from FGD gypsum. The adsorption behaviors of FGD gypsum for Pb(II) and Cd(II) such as pH impact, sorption kinetics, sorption isotherms and sorption thermodynamics were studied in a series of batch experiments. The pH studies indicated that the adsorption of Pb(II) and Cd(II) had their best adsorption amounts both at the pH values from 5.0 to 7.0. The kinetic analysis displayed that the adsorption processes both followed the pseudo-second order model well, and the FGD gypsum provided a higher sorption rate for Pb(II). Equilibrium studies showed that the adsorption of Pb(II) and Cd(II) could be properly described by Langmuir isotherms model, and the predicted maximum adsorption capacities were even greater than some specially prepared adsorbents. The thermodynamic investigation confirmed that the removal of Pb(II) and Cd(II) from aqueous medium could carry out spontaneously, and the higher temperature favored the processes. The instrument analysis techniques were also employed to deeply understand the mechanism involved in Pb(II) and Cd(II) removal by FGD gypsum. Overall, good sorption performance together with cost-effective characteristic makes FGD gypsum potentially attractive material for the Pb(II) and Cd(II) removal in industrial wastewater.

Flue gas desulfurization (FGD) gypsum, a familiar waste generated from coal-fired power plants, was successfully transformed to hydroxyapatite (FGD-HAP) by hydrothermal method. The obtained FGD-HAP was characterized by XRD, FTIR, TEM and BET methods and investigated as adsorbent for removal of Pb(2+) and Cd(2+) from wastewater. Batch experiments were performed by varying the pH values, contact time and initial metal concentration. The result of pH impact showed that the adsorption of two ions was pH dependent process, and the pH 5.0-6.0 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies displayed that the pseudo-second order kinetic model could describe adsorption processes well with high correlation coefficient, and the Langmuir isotherm model provided the best fit to the equilibrium experimental data. The maximum adsorption capacities calculated from Langmuir equation were 277.8 and 43.10mg/g for Pb(2+) and Cd(2+), respectively, which can compete with other adsorbents. The thermodynamic parameters revealed the adsorption processes were endothermic and spontaneous in nature. In binary adsorption, the amount of Cd(2+) adsorbed on FGD-HAP decreased by 46.0% with increasing concentration of Pb(2+), which was higher than that of Pb(2+)(21.7%), demonstrating the stronger affinity between FGD-HAP and Pb(2+). The highest amount of Pb(2+) and Cd(2+) desorbed from saturated FGD-HAP by EDTA solution confirmed the FGD-HAP was a promising alternative adsorbent in treatment of toxic Pb(2+) and Cd(2+) wastewater.

Porous matrix immobilization is considered as an effective approach to address the engineering challenges during practical application of nanoadsorbent. In this work, polyethersulfone (PES) beads with diameter of around 2.5 mm, in which nanosized amine-rich polymer spheres (APSs) with particle size of ∼400 nm are immobilized, are fabricated via phase inversion route. APSs-PES beads possess asymmetric and hierarchical structure with an exterior porous surface dense layer and numerous inner interpenetrating fingerlike channels, which promote the transportation of molecule and prevent the leaching of nanoadsorbents. The well distributed APSs with nitrogen-containing functional groups provide abundant adsorption sites. The cooperative attributing of the hierarchical structure and APSs demmonstrates enhanced Cr (VI) adsorption efficiency. The adsorption capacity of Cr (VI) is 243.9 mg/g at 298 K by Langmuir fitting. The effects of pH, temperature, the ratio of adsorbents and coexisting ionic are further studied in detail. The Cr (VI) removal mechanism is further explored by the combination of SEM, XPS, FTIR measurements and the adsorption parameters, further revealing the synergistic contribution of electrostatic attraction and reduction process. Therefore, this kind of adsorbents may show promising prospects on elimination of hazardous Cr (VI) in wastewater treatment.

In this work, an iron-tannin-framework (ITF) complex was introduced to a poly (ether sulfone) (PES) casting solution as a hydrophilic additive to fabricate ITF/PES ultrafiltration (UF) membranes via non-solvent-induced phase separation (NIPS). The structure and performance of the PES membranes with ITF concentrations ranging from 0 to 0.9wt.% were systematically investigated by scanning electron microscopy, water contact angle, permeability, protein rejection and fouling resistance measurements. The results indicate that the pore structure and surface properties of PES UF membranes can be regulated by incorporating the ITF complex. Compared with classical PES membranes, ITF/PES membranes were found to have an increased hydrophilicity and porosity and reduced surface pore size. Importantly, a simultaneous enhancement of permeability and separation performance was observed for the blend membranes, which indicates that the introduction of the ITF complex can break through the trade-off between permeability and selectivity of UF membranes.When the ITF content was 0.3wt.%, the permeability reached a maximum of 319.4(L/m2h) at 0.1MPa, which is 1.6 times higher than that of the classical PES membrane. Furthermore, the BSA rejection increased from 25.9% for the PES membrane to 95.9% for the enhanced membrane. In addition, the same membrane showed an improved fouling resistance (higher flux recovery and lower adhesion force) and stable hydrophilicity (unchanged after incubation in deionized water for 30days). The simple, green and cost-effective preparation process and the outstanding filtration performance highlight the potential of ITF/PES membranes for practical applications.

Mesoporous silica materials with a centered rectangular symmetry (cmm) have been synthesized through a facile direct-templating method using tetraethylorthosilicate (TEOS) and amphiphilic block co-polymers Pluronic P123 under acidic conditions. The amino groups have been grafted to as-synthesized mesoporous silica by [1-(2-amino-ethyl)-3-aminopropyl]trimethoxysilane (AAPTS). Thus obtained amino-functionalized mesoporous silica (denoted as NN-silica) was used for sequestration of Cr(VI) from aqueous solution. After sequestration of Cr(VI), the sample was denoted as Cr(VI)-silica. The parent mesoporous silica, NN-silica and Cr(VI)-silica were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and N(2) adsorption-desorption isotherms. XRD and TEM results confirm that the structure of these samples is centered rectangular symmetry (cmm). N(2) adsorption-desorption isotherms show that there is a remarkable decrease in surface area and pore volume for NN-silica (S(BET)=54.5 m(2)g(-1), V(P)=0.09 cm(3)g(-1)) and Cr(VI)-silica (S(BET)=53.2 m(2)g(-1), V(P)=0.07 cm(3)g(-1)) compared to the parent mesoporous silica (S(BET)=444.0 m(2)g(-1), V(P)=0.71 cm(3)g(-1)). The BJH desorption average diameter of NN-silica, Cr(VI)-silica and the parent mesoporous silica is 4.40 nm, 4.07 nm and 5.11 nm, respectively. The results reveal the channels of as-synthesized mesoporous silica are essentially grafted with abundant amino groups and loaded with Cr(VI). The adsorption experiment results show that the functionalized mesoporous silica materials possess an increased Cr(VI) adsorption capacity and the maximum Cr(VI) loadings at 25, 35 and 45 degrees C can reach 2.28, 2.86 and 3.32 mmol/g, respectively.

Recently, inorganic nanoparticles blended within polymeric membranes have shown improved antifouling performance in wastewater treatment. However, agglomeration of nanoparticles remains as one of the major obstacles for generating a uniform surface. In this study, a new method for in situ preparation of Al-containing PVDF ultrafiltration membranes to improve the dispersion of nanoparticles is reported. The strategy of this method is to combine sol–gel process with traditional immersion precipitation process. Al sol was synthesized by the addition of anionic exchange resin in N,N-dimethylformamide (DMF) solvent containing aluminum chloride. Homogeneous Al-containing PVDF casting solution was then obtained by dissolving PVDF polymer in the Al sol. The membrane formation mechanism was investigated by precipitation kinetics and morphology. Results indicate that the addition of Al species can accelerate phase inversion of casting solution. Scanning electron microscopic images show that a typical transition from sponge-like structure to finger-like structure occurred with increasing Al species content. The existence and dispersion states of Al species in the resultant membrane matrix were further examined by transmission electron microscope and X-ray photoelectron spectrometer. The results indicate the Al species nanoparticles were well dispersed throughout PVDF matrix. Dynamic BSA fouling resistance experiments demonstrate the Al-containing PVDF membranes possess improved separation performances over the pure PVDF membranes.

This paper reports on a new method for the preparation of mesoporous silica membranes on alumina hollow fibers. A surfactant-silica sol is filled in the lumen of an alpha-alumina hollow fiber. The filtration technique combined with an evaporation-induced self-assembly (EISA) process results in the formation of a continuous ordered mesoporous silica layer on the outer side of alpha-alumina hollow fibers. X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen isothermal adsorption measurements reveal that these membranes possess hexagonal (P6mm) mesostructures with pore diameters of 4.48 nm and BET surfaces of 492.3 m(2) g(-1). Scanning electron microscopy (SEM) studies show that the layers are defect free and energy-dispersive spectroscopy (EDS) mapping images further confirm the formation of continuous mesoporous silica layer on the outer side of alpha-alumina hollow fibers. Nitrogen and hydrogen permeance tests show that the membranes are defect free.