Gas-phase isopropanol degradation by nonthermal plasma combined with Mn-Cu/-Al2O3.

In this study, the dielectric barrier discharge (DBD) induced by nonthermal plasma (NTP) technology was used for isopropanol (IPA) degradation. IPA, intermediate, final product, and ozone concentrations were analyzed using GC-MS, carbon dioxide detector, and ozone detector. The experimental flow rate and concentration were fixed to 1 L/min and 1200 ppm ± 10%, respectively. Different reaction procedures were proposed for self-made metal catalyst combined with a plasma system (plasma alone and γ-Al2O3 combined with plasma, Cu (5 wt%)/γ-Al2O3 combined with plasma, Mn (3 wt%)-Cu (5 wt%)/γ-Al2O3 combined with plasma). In addition, the effect of the carrier gas oxygen content (0%, 20%, and 100%) on IPA conversion and intermediate and carbon dioxide selectivity was also investigated. The results revealed that the Mn (F)-Cu/γ-Al2O3 combined with plasma exhibited more efficient IPA conversion. In the 100% oxygen environment, the IPA conversion rate increased from 79.32 to 99.99%, and carbon dioxide selectivity increased from 3.82 to 50.23%. IPA was completely converted after 60 min of plasma treatment with the acetone selectivity, carbon dioxide selectivity, and tail ozone concentration of 26.71% ± 1.27%, 50.23% ± 0.56%, and 1761 ± 11 ppm, respectively. This study proved that the current single planar DBD configuration is an effective advanced treatment technology for the decomposition of VOCs.

Rapid and efficient removal/recovery of molybdenum onto ZnFe2O4 nanoparticles.

An efficient method for removing and recovering molybdenum (Mo) from water was developed by using ZnFe2O4 nanoparticles. The Mo adsorption displayed a nonlinear isotherm that fitted well with the Langmuir isotherm, showing limited adsorption sites on the surface of ZnFe2O4. The adsorption of Mo(VI) was dependent on solution pH. With increasing pH, the build-up of negative charges of both adsorbent and adsorbate led to enhanced electric repulsion between them. The K-edge XANES spectra for the adsorbents collected after Mo adsorption revealed that Mo(VI) was the predominant oxidation state sorbed on ZnFe2O4, indicating that the reduction of Mo(VI) did not occur on ZnFe2O4. The different peak positions of k-space and R-space shown in K-edge EXAFS spectra demonstrated that the adsorbed Mo could be bound on the surface or be slipped in the vacancy position of the ZnFe2O4 crystal. Importantly, Mo could be efficiently adsorbed from photoelectric industrial wastewater and these adsorbed Mo anions were rapidly replaced by OH(-) ions, implying the potential for Mo removing and recovering in industrial wastewater.

Conversion of waste Mn-Zn dry battery as efficient nano-adsorbents for hazardous metals removal.

A novel technique was successfully developed for manufacturing Mn-Zn ferrite nano-particles by acid dissolution and ferrite processes. The powders of waste dry batteries (PWDBs) were used as starting raw materials because the Mn and Zn content inside the PWDBs is potentially high. Our data showed that the most abundant elements inside PWDBs are manganese (41.0%), oxygen (40.6%), zinc (15.3%), and carbon (3.1%). It was found that proper reductant was critical for dissolution where FeSO4 is essential for spinel ferrite formation. Synthesized Mn-Zn ferrite particles reached their saturation magnetization at 63.8 emu/g and were successfully applied for As, Cd, and Pb removal in aqueous solution. Under the conditions of Mn-Zn ferrite 0.005 g, volume 10 mL, temperature 27°C, and contact time 1h, As, Cd, and Pb removal could reach 99.9, 99.7, and 99.8%, respectively. We demonstrate a novel method that can be applied for transforming WDBs into resource materials. This not only reduces the amount of WDBs, but also supports the concept of waste-battery reusable green-energy policy.

XANES evidence of arsenate removal from water with magnetic ferrite.

Arsenic (As) in groundwater and surface water is a worldwide problem possessing a serious threat to public health. In this study, a magnetic ferrite, was synthesized and investigated for its As(V) removal efficiency. The adsorption of As(V) by magnetic ferrite exhibited an L-shaped nonlinear isotherm, suggesting limiting binding sites on the adsorbent surface. The As K-edge X-Ray Absorption Near-Edge Structure (XANES) revealed that the adsorbed As(V) on ferrite was not reduced to more toxic As(III) by Fe(2+) in the ferrite structure. The maximum As adsorption capacity of ferrite was 14 mg/g at pH 3 and decreased with increasing pH due to enhanced electrostatic repulsion between As(V) and the adsorbent surface. Desorption of As(V) using six different acid and salt solutions showed that the desorption rate decreased in an order of H3PO4 > Na3PO4 > H2SO4 > Na2SO4 > HCl > HNO3. These results suggest that magnetic ferrite without surface modification is an effective adsorbent for removing As(V) from water, which was confirmed by the effective removal of As(V) from contaminated groundwater using this material. The used material can then be recovered using a magnet because of its paramagnetism; the adsorbed As(V) on the material can be recovered using H3PO4 or Na3PO4 solutions.

Kinetics and thermodynamics of adsorption for Cd on green manufactured nano-particles.

Magnetic nano-particles CuFe(2)O(4) were successful manufactured from industrial sludge by combination of acid leaching, chemical exchange, and ferrite process. For the first time these recycled nano-particles were used as adsorbent to investigate the kinetics and thermodynamics for adsorption of Cd in aqueous solutions. These experimental results showed that Cd(2+) adsorption efficiency increased from 0.85 to 99.9% when pH increased from 2 to 6. The maximum adsorption capacity of Cd(2+) was found to be 17.54 mg g(-1) under the conditions at pH 6.0, contact time 30 min, and temperature 318 K. The pseudo-second-order kinetic model provides the best correlation with the experimental data compared to the pseudo-first-order model. The Langmuir model yields a better fitting than the Freundlich model for Cd(2+) adsorption on CuFe(2)O(4) nano-particles under investigated temperatures. The thermodynamic constants of the adsorption process were evaluated, ΔG°, ΔH° and ΔS° is -6.05 kJ mol(-1) (at 318 K), 0.71 kJ mol(-1), and 4.53 J mol(-1) K(-1), respectively. These results imply that Cd(2+) adsorption onto CuFe(2)O(4) is feasible, spontaneous and endothermic in nature.

Combustion of isopropyl alcohol using a green manufactured CuFe2O4.

A green method for manufacturing CuFe(2)O(4) from industrial Cu sludge was successfully developed by a combination of acid leaching, chemical exchange and ferrite process. The CuFe(2)O(4) was applied for combustion of volatile organic compounds (VOCs) derived from isopropyl alcohol (IPA). The results show that IPA was reacted to form intermediate acetone and CO(2) at the temperature range of 110-170°C. When the temperature was increased to 180°C, IPA can be 100% converted into CO(2). The 96-h decay tests indicated that the catalyst has a good thermal stability and durability under the conditions of gas hourly space velocity 30,000 h(-1), oxygen content 21%, IPA inlet concentration 2000 ppm, and reaction temperature 180°C. The results demonstrate great potential that our manufactured CuFe(2)O(4) catalyst can be used in combustion IPA streams to eliminate the emission of IPA.

Treatment of complex heavy metal wastewater using a multi-staged ferrite process.

Complete removal of heavy metal from complex heavy-metal wastewater (CHMW) requires advanced technology. This study investigated the feasibility of a multi-staged ferrite process (MSFP) for treating CHMW, containing Cd, Cu, Pb, Cr, Zn, Ag, Hg, Ni, Sn and Mn. Our experimental results showed that most of the supernatants after conventional single-step ferrite process could conform to the effluent standard of Environmental Protection Administration in Taiwan. However, the sludge could not satisfy the toxicity characteristic leaching procedure (TCLP) limits due to high Cd, Cu, and Pb concentrations. The performance of MSFP in removing heavy metals from wastewater was subsequently investigated and the parameters of three treating steps in MSFP were optimized under 70°C and 90°C at pH 9, and 80°C at pH 10. After the three-staged procedures, all heavy metals in supernatant and sludge could fulfill the contamination levels regulated by law. In addition, the sludge generated from the MSFP was examined by XRD and forms a stable spinel structure, which could be effectively separated by external magnetic field.

Recycling of Cu powder from industrial sludge by combined acid leaching, chemical exchange and ferrite process.

A method in combination of acid leaching, chemical exchange and ferrite process was applied to recycle copper and confer higher chemical stability to the sludge generated from etching process in printed circuit board industry. Ninety-five percent copper could be recycled in the form of powder from the sludge. Moreover, not only the wastewater after chemical exchange can be treated to fulfill the effluent standard, but also the sludge can satisfy the toxicity characteristic leaching procedure (TCLP) limits made by Taiwan's environmental protection administration.