Additive manufacturing of electrodes for desalination

Capacitive deionization (CDI) is an energy-efficient process for desalination of brackish (low-salinity) waters, and will be able to meet the freshwater demands of agriculture, industry, and potable water. One of the key challenges in widespread adoption of CDI is mechanical reliability of the electrodes manufactured by additive manufacturing processes. Mechanical reliability of electrodes depends on the optimal chemical composition of activated carbon-based electrode material. Traditional materials used for CDI electrodes are known to have adverse environmental effects from solvents such as N-Methyl-2-pyrrolidone (NMP) and Dimethyl sulfoxide (DMSO), and fluorine containing binders such as polyvinylidene difluoride (PVDF). In this paper we present (1) electrodes based on 'green chemistry' with reduced environmental impact, (2) stable chemical composition of electrodes with required mechanical reliability. We present the alternative CDI electrode composition using activated carbon, toluene as solvent, and polyvinyl butyral (PVB) as binder. We also mixed ion-exchange resins to produce composite electrode materials with toluene and PVB, which showed similar salt removal characteristics as composite electrodes with PVDF and NMP. Thus, the new electrode composition is a viable alternative for sustainable additive manufacturing of CDI electrodes with mechanical reliability and reduced environmental impact

CO-sensing properties of a NASICON-based gas sensor attached with Pt mixed with Bi2O3 as a sensing electrode

NASICON (Na3Zr2Si2PO12)-based gas sensors capable of detecting various gases (CO2, NO2, Cl2, VOC and so on) have so far been developed by many researchers. In this study, planar-type gas sensors using a NASICON disc attached with Pt mixed with Bi2O3 as a sensing electrode (Pt(nBi2O3), n (0.01?30): the amount of Bi2O3 addition (wt%)) and Pt as a reference electrode were fabricated, and their sensing properties to CO and H2 were examined in the operating temperature range of 25?300 °C in dry and wet air. The sensors obtained were denoted as Pt(nBi2O3)/Pt. All Pt(nBi2O3)/Pt sensors fabricated responded to CO at all operating temperatures tested, and the magnitude of CO response increased with a decrease in the operating temperature. In addition, the magnitude of CO response largely depended on the additive amounts of Bi2O3 to the Pt sensing electrode. The increase in the additive amount of Bi2O3 to the Pt sensing electrode (0.01 ? n ? 1) enhanced markedly the magnitude of CO response, 90% response time and CO selectivity against H2. The Pt(1Bi2O3)/Pt sensor showed a linear relationship between the CO response and the logarithm of CO concentration (1?3000 ppm) in dry air at 25 °C and the CO selectivity against H2 was enhanced in wet air, in comparison with those observed in dry air. The interfacial layer, which was formed between the NASICON and the Pt(1Bi2O3) electrode, was suggested to play an important role in improving of the CO-sensing properties

Catalytic degradation of a plasticizer, di-ethylhexyl phthalate, using Nx–TiO2−x nanoparticles synthesized via co-precipitation

There is an increasing concern in the decontamination of wastewater. Most of the advanced oxidation procedures described so far are based on the use of different oxidation reactions including photocatalysis and ozonation. Doped titanium dioxide nanoparticles are photoactive under visible light illumination, being therefore possible to harvest solar energy for water decontamination. In this study, anatase Nx–TiO2−x nanoparticles were successfully synthesized by a simple co-precipitation procedure based on the oxidation of titanous (III) chloride in the presence of ammonia. The transmission electron microscope images of Nx–TiO2−x show nanoparticles with an average diameter size of ∼13 nm. The presence of nitrogen (N1s) was verified using XPS analysis. The characteristic peak at 400 eV indicates the formation of O–Ti–N bonds. The Nx–TiO2−x nanoparticles were found to be useful for the removal of a wastewater pollutant use as plasticizer (di-ethylhexyl phthalate) by a combined process of heterogeneous photocatalysis under visible illumination coupled with ozonation. The photoactivity of the Nx–TiO2−x nanopowder is enhanced compared to commercial TiO2 P25 nanoparticles due to the generation of electron/hole pairs under visible irradiation together with a larger electrocatalytic activity towards oxygen reduction.The research described herein was Financially Supported by the National Science Council (NSC) in Taiwan under the Contract No. of 101-2221-E-035-031-MY3. S.A. also thanks the Feng Chia University, Taiwan, for the Visiting Professor appointment. The authors, SA and TV thank Ministry of India and Spain for the sanction of India–Spain collaborative Research Grant (DST/INT/Spain/P-37/11 dt. 16th Dec 2011)

Sunlight assisted degradation of methylene blue dye by zinc oxide nanoparticles green synthesized using Vitex negundo plant leaf extract

Zinc oxide nanoparticles (ZnO NPs) were formed through a simple green synthesis route using Vitex negundo (V. negundo) leaf extract as reducing and capping source. Morphological, structural, chemical and optical features of the prepared ZnO NPs were examined by field emission SEM, XRD, EDAX, PL, FTIR and UV–vis DRS, respectively. FESEM images precisely visualized morphology of the ZnO NPs as spherical with particles size ranges between 5 and 35 nm having a mean diameter of ∼ 19 nm. XRD pattern revealed formation of hexagonal wurtzite structured ZnO NPs with high crystallinity. Further, the observed asymmetric stretching vibration of Zn-O bond confirmed the formation of hexagonal wurtzite structured ZnO NPs. Photocatalytic activity of the ZnO NPs was assessed against methylene blue (MB) dye degradation under natural sunlight illumination. Results of the photocatalytic experiment disclosed an impressive MB dye degradation efficiency of 98.50 % at 60 min. Moreover, green synthesized ZnO NPs exhibited a maximum mineralization (TOC removal) efficiency of 92.34 % at 5 h of sunlight illumination

Cow dung extract as a low-cost and natural sensitizer for zinc oxide nanoparticles photoanode based dye-sensitized solar cell: A novel initiative for waste to energy conversion

Cow dung extracts are prepared using ethanol and methanol as solvents. Electronic absorption spectra of cow dung extracts have exhibited wide absorption in the UV and visible region between 300 and 730 nm. The absorption of cow dung extracts showed variations in intensity and absorption peaks at different wavelengths, which can be attributed to presence of diverse photosynthetic pigments corresponding to polarity of applied solvents. The observed pigments of chlorophyll a, chlorophyll b and carotenoids in the cow dung extracts can be ascribed to the feeding behavior of the cow. The FTIR and UV–vis absorption results have disclosed that the sensitization of zinc oxide nanoparticles (ZnO NPs) photoanode is mainly due to the chlorophylls present in the cow dung extract. The methyl group in the chlorophyll molecules from ideal bond with ZnO NPs that enables transfer of electrons from chlorophyll molecules to conduction band of ZnO NPs. The solar cells sensitized with cow dung extract in methanol has delivered highest energy conversion efficiency of 0.102%, which can be ascribed to presence of relatively a greater number of photosynthetic pigments

Sparingly Soluble Constant Carbonate Releasing Inert Monolith for Enhancement of Antimicrobial Silver Action and Sustainable Utilization

Silver, a metal with phenomenal commercial importance has been exploited in its ionic form in the field of water purification, with the objective of delivering microbially safe drinking water. Silver released at such concentrations is unrecoverable and has to be reduced to ensure sustainable utilization of the metal. We have shown that small concentrations of carbonate can effectively bring down the amount of silver ion used for microbial disinfection by half. Implementation of this finding requires constant carbonate releasing materials in natural water for an extended period. In this work, we describe a hybrid material with intrinsically high stability in water that is prepared using naturally abundant ingredients which releases carbonate constantly and in a controlled fashion. This composition in conjunction with reduced silver ion concentration delivers mircobially safe water, tested with <i>E. coli</i> and MS2 phage. Use of constant carbonate releasing material for antimicrobial applications can reduce the unrecoverable silver released into the environment by ∼1300 tons/year. We also show that the composition can be modified to release cations of choice without disturbing the CO₃^2– release from the same. A sustained release of selective cations along with carbonate can supplement drinking water with the minerals of interest

Ultra-small Ni@NiFe2O4/TiO2 magnetic nanocomposites activated peroxymonosulphate for solar light-driven photocatalytic mineralization of Simazine

In the heterogeneous photocatalytic degradation of environmental contaminants the recovery, reuse of employed nanocatalyst was crucial and it is essentially required for the scale up applications. Besides, designing a magnetic material with heterojunction that can effectively oxidize the toxic organic contaminants to non-toxic substance under different reaction conditions including direct solar light irradiation remains a challenge. Considering the above facts, herein, we tailored heterojunction between the magnetic materials and non-magnetic materials with ultra-small Ni nanoparticles modified NiFe2O4/TiO2 nanostructures (Ni@NiFe2O4/TiO2 magnetic nanocomposites) through a simple sonochemical route. The Raman phonons at ∼ 540 cm−1 consistent to nickel metal nanoparticles and the spinel ferrites crystal structure confirmed the formation of Ni@NiFe2O4/TiO2 magnetic nanocomposites. The reduced optical bandgap of the resulting nanocomposites indicated the effective absorption of direct solar light irradiation when compared to the bare TiO2. Thus in-turn, enhanced the photocatalytic efficiency of simazine degradation in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 11.0 × 10–4 s−1) and augmented the activation of peroxymonosulphate (PMS) in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 32.5 × 10–4 s−1). Ni@NiFe2O4/TiO2 +PMS exhibited 3 folds enhanced efficiency in the presence of sunlight. The as-prepared NiFe2O4/TiO2 magnetic nanocatalysts were more stable and the efficiency of simazine oxidation was approximately same for the continuous five cycles at the optimized experimental conditions. The Ni@NiFe2O4/TiO2 magnetic nanocomposites preparation and the activation of PMS may promise the applications in an efficient wastewater treatment

Sparingly Soluble Constant Carbonate Releasing Inert Monolith for Enhancement of Antimicrobial Silver Action and Sustainable Utilization

Silver, a metal with phenomenal commercial importance has been exploited in its ionic form in the field of water purification, with the objective of delivering microbially safe drinking water. Silver released at such concentrations is unrecoverable and has to be reduced to ensure sustainable utilization of the metal. We have shown that small concentrations of carbonate can effectively bring down the amount of silver ion used for microbial disinfection by half. Implementation of this finding requires constant carbonate releasing materials in natural water for an extended period. In this work, we describe a hybrid material with intrinsically high stability in water that is prepared using naturally abundant ingredients which releases carbonate constantly and in a controlled fashion. This composition in conjunction with reduced silver ion concentration delivers mircobially safe water, tested with <i>E. coli</i> and MS2 phage. Use of constant carbonate releasing material for antimicrobial applications can reduce the unrecoverable silver released into the environment by ∼1300 tons/year. We also show that the composition can be modified to release cations of choice without disturbing the CO₃^2– release from the same. A sustained release of selective cations along with carbonate can supplement drinking water with the minerals of interest