Reduction of Hexavalent Chromium in Water Using Iron-Aluminum Bimetallic Particles

2013 ◽  
Vol 849 ◽  
pp. 142-146 ◽  
Author(s):  
Shin Shian Chen ◽  
Yi Chu Huang ◽  
Tai Yu Chen
Keyword(s):  
Hexavalent Chromium ◽  
Ph Value ◽  
Chemical Precipitation ◽  
Metal Species ◽  
X Ray Diffraction ◽  
Reduction Potentials ◽  
Iron Aluminum ◽  
Fe Content ◽  
Initial Ph ◽  
High Reduction

Metal finishing wastewater containing chromium was conventionally treated by chemical precipitation and ion exchange techniques. Zero-valent metals such as iron, aluminum, zinc that possess high reduction potentials are frequently employed to remediate and process the contaminated groundwater. Iron-aluminum bimetallic metal (Fe-Al) is developed to improve the reduction capacity of Fe, Al is regarded as the electron supplier to prevent the precipitates formed on the surface of Fe. The aim of this research is to study the performance of Fe-Al on the reduction of hexavalent chromium ion (Cr6+) in water under several operation parameters including initial pH value, dosage of Fe-Al to Cr6+ ratio (Fe-Al/Cr+6), and Fe contents of Fe-Al particles. The results indicated that the sizes and specific surface area of Fe-Al particles increased with higher Fe content. The metal species on the surface of Fe-Al particles were identified by an x-ray diffraction spectrometer (XRD). Reduction of Cr6+ with Fe-Al particles consumes the H+ in water resulting in the increase of pH value with the reaction time. The study showed that the reduction potentials of Fe-Al on Cr6+ are promoted under acidic state and with higher dosage of Fe-Al/Cr+6.

scholarly journals The Removal of Methylene Blue Dye from Aqueous Solutions Using Activated and Non-Activated Bentonites

2003 ◽  
Vol 21 (5) ◽  
pp. 451-462 ◽  
Author(s):  
Sameer Al-Asheh ◽  
Fawzi Banat ◽  
Leena Abu-Aitah
Keyword(s):  
Methylene Blue ◽  
Ph Value ◽  
Sodium Dodecyl ◽  
Freundlich Isotherm ◽  
Blue Dye ◽  
Batch Adsorption ◽  
Ionic Surfactant ◽  
Methylene Blue Dye ◽  
X Ray Diffraction ◽  
Initial Ph

An improvement in the adsorption capacity of naturally available bentonite towards water pollutants such as Methylene Blue dye (MBD) is certainly needed. For this purpose, sodium bentonite was activated by two methods: (1) treatment with sodium dodecyl sulphate (SDS) as an ionic surfactant and (2) thermal treatment in an oven operated at 850°C. Batch adsorption tests were carried out on removing MBD from aqueous solution using the above-mentioned bentonites. It was found that the effectiveness of bentonites towards MBD removal was in the following order: thermal-bentonite > SDS-bentonite > natural bentonite. X-Ray diffraction analysis showed that an increase in the microscopic bentonite platelets on treatment with SDS was the reason behind the higher uptake of MBD. An increase in sorbent concentration or initial pH value of the solutions resulted in a greater removal of MBD from the solution. An increase in temperature led to an increase in MBD uptake by the bentonites studied in this work. The Freundlich isotherm model was employed and found to represent the experimental data well.

Characterization of Nano-Biphasic Calcium Phosphates Synthesized under Microwave Curing

2008 ◽  
Vol 3 ◽  
pp. 67-87 ◽  
Author(s):  
Wafa I. Abdel-Fattah ◽  
Fikry M. Reicha ◽  
Tarek A. Elkhooly
Keyword(s):  
Ph Value ◽  
Calcium Phosphates ◽  
Chemical Precipitation ◽  
Calcium Deficiency ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Curing ◽  
Tcp Phase ◽  
Diffraction Patterns

Two biphasic BCP ceramic samples were synthesized by chemical precipitation and microwave curing of calcium deficient hydroxyapatite CDHA under the same pH value and temperature but varied in their initial Ca/P molar ratio. Precipitates were characterization after thermogravimetric analysis, fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption spectroscopy and TEM. Hydroxyapatite (HA) contents were measured for the two biphasic calcium phosphate (BCP) ceramics by sintering the calcium-deficient apatites (CDHA). The results reveal two condensation mechanisms of HPO42- affecting the Ca/P molar ratio after calcination. The X-ray diffraction patterns of BCP powders show the in situ formation of -TCP in the BCP powder. The amount of -TCP phase increases as the initial Ca/P molar ratio decreases due to more calcium deficiency in CDHA structure. The influence of HPO42- incorporation on increasing -TCP phase content after calcination is evaluated. TEM micrographs proved the effect of microwave curing during the preparation process on reducing of particle size to nanoscale range and the destruction of CDHA to finer HA and -TCP particles upon calcination.

scholarly journals Degradation of Acid Red B by Manganese doped iron oxychloride and Permonosulfate: Performance and Inhomogeneous Activation Mechanism

2021 ◽  
Author(s):  
Rong Chen ◽  
Dan Zhao ◽  
Yanmao Dong ◽  
Chengrun Cai ◽  
Yan Yuan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Ph Value ◽  
Active Species ◽  
Ion Concentration ◽  
Activation Mechanism ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Initial Ph

Abstract manganese doped iron oxychloride (Mn-FeOCl) was synthesized by partial pyrolysis method. The Mn-FeOCl was used as heterogeneous catalyst to activate permonosulfate (PMS) for the degradation of azo dye acid red B(ARB) for the first time. The Mn-FeOCl was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD). The effects of Mn-FeOCl dosage, PMS concentration, initial pH value, Cl ion concentration and humic acid (HA) dosage on the degradation of ARB by Mn-FeOCl/PMS were investigated. Results showed that the ARB was degraded effectively by Mn-FeOCl/PMS. The mineralization rate of ARB reached 42.5%. As the Mn-FeOCl dosage was 0.1g/L, PMS concentration was 1mmol/L, and ARB concentration was 0.05mmol/L, the degradation rate of ARB reached 99.4% in 30 minutes. With the increase of PMS dosage, Mn-FeOCl dosage, Cl− ion concentration and initial pH value, the decolorization effect of ARB increased. The reaction mechanism was analyzed by free radical quenching experiment and XPS. The main active species were determined as ·OH and SO4·− which generated by PMS activation. The SO4·−−was the main active species.

scholarly journals Ammonium Recovery from Biocatalytic Calcification Reactor Effluent by Struvite Precipitation

2017 ◽  
Vol 19 (2) ◽  
pp. 251-256 ◽  
Keyword(s):  
Ph Value ◽  
Ammonium Phosphate ◽  
Chemical Precipitation ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Magnesium Ammonium Phosphate ◽  
Magnesium Ammonium ◽  
S Period ◽  
Slow Mixing ◽  
Biological Methods

Chemical precipitation is a suitable method for the recovery and removal of ammonium in water and a fertilizer known as MAP (magnesium ammonium phosphate; MgNH4PO4.6H2O; struvite) is obtained. Additionally, the advantage of this method is that environmental conditions do not have any effect compared to biological methods. In this study, the recovery of ammonium (Cmean=348 mg NH4 +/L ± 38.1; n=25) occurred after the hydrolysis of urea in the biocatalytic calcification reactor (BCR) effluent and it precipitated as struvite. The effects of operating parameters, such as different phosphate and magnesium sources, Mg2+:NH4+:PO43- molar ratio, pH value, mixing speed-time, and fertilizer effect, were examined. The precipitates were characterized by X-ray diffraction and scanning electron micrograph. The optimum molar ratio of Mg2+:NH4+:PO43− was determined as 1.25:1:1. Studies using different pH ranges (7–10) and this molar ratio showed that the ammonium recovery of approximately 96% was reached at a pH value of 9.36. It was seen that the rapid mixing (200 rpm) of 30-s period and the slow mixing (30 rpm) of 2-min period were sufficient for MAP precipitation. Struvite that was obtained after precipitation was used as a fertilizer and it was observed to have a positive effect on plant growth.

Removal of sulfate from wet FGD wastewater by co-precipitation with calcium hydroxide and sodium aluminate

2018 ◽  
Vol 77 (5) ◽  
pp. 1336-1345 ◽  
Author(s):  
Jicheng Yu ◽  
Jia Lu ◽  
Yong Kang
Keyword(s):  
Ph Value ◽  
Sodium Aluminate ◽  
Chemical Precipitation ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Operation Condition ◽  
Sulfate Removal ◽  
Aluminum Hydroxides ◽  
Initial Ph ◽  
Co Precipitation

Abstract Chemical precipitation method was adopted to remove sulfate from wet flue gas desulfurization (FGD) wastewater and mixtures of Ca(OH)2 (CH) and NaAlO2 (SA) were used as precipitants. The mechanisms of sulfate removal were explored according to the experimental and simulated results. These showed that three kinds of precipitations, which were gypsum, ettringite and co-precipitation onto aluminum hydroxides, were formed when sulfate in water reacted with CH and SA. The optimum operation condition for removing sulfate was that the molar ratio of CH/SA was 2, the initial pH value 5, the precipitant dosage 15 g/L, the reaction time 20 min, and the reaction temperature 55 °C. The sulfate was reduced from 4,881 mg/L to 784 mg/L under the optimized condition. In addition, the heavy metals and fluoride were also mostly removed. The post treatments of the supernatant illustrated that removal of sulfate from wet FGD wastewater by co-precipitation with CH and SA was a better choice.

Hexavalent chromium reduction and energy recovery by using dual-chambered microbial fuel cell

2014 ◽  
Vol 71 (3) ◽  
pp. 353-358 ◽  
Author(s):  
Praveena Gangadharan ◽  
Indumathi M. Nambi
Keyword(s):  
Fuel Cell ◽  
Microbial Fuel Cell ◽  
Hexavalent Chromium ◽  
Ph Value ◽  
Anaerobic Sludge ◽  
Anode Chamber ◽  
Ambient Conditions ◽  
Carbon Reduction ◽  
Organic Electron ◽  
Initial Ph

Microbial fuel cell (MFC) technology is utilized to treat hexavalent chromium (Cr(VI)) from wastewater and to generate electricity simultaneously. The Cr(VI) is bioelectrochemically reduced to non-toxic Cr(III) form in the presence of an organic electron donor in a dual-chambered MFC. The Cr(VI) as catholyte and artificial wastewater inoculated with anaerobic sludge as anolyte, Cr(VI) at 100 mg/L was completely removed within 48 h (initial pH value 2.0). The total amount of Cr recovered was 99.87% by the precipitation of Cr(III) on the surface of the cathode. In addition to that 78.4% of total organic carbon reduction was achieved at the anode chamber within 13 days of operation. Furthermore, the maximum power density of 767.01 mW/m2 (2.08 mA/m2) was achieved by MFCs at ambient conditions. The present work has successfully demonstrated the feasibility of using MFCs for simultaneous energy production from wastewater and reduction of toxic Cr(VI) to non-toxic Cr(III).

scholarly journals Characterization of Biochars Produced by Co-Pyrolysis of Hami Melon (Cantaloupes) Straw Mixed with Polypropylene and Their Adsorption Properties of Cadmium

2021 ◽  
Vol 18 (21) ◽  
pp. 11413
Author(s):  
Changheng Li ◽  
Qing Huang ◽  
Haixiang Zhang ◽  
Qingqing Wang ◽  
Rixin Xue ◽  
...  
Keyword(s):  
Xrd Analysis ◽  
Chemical Precipitation ◽  
Batch Adsorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Weight Percentage ◽  
Mixing Ratios ◽  
Initial Ph ◽  
Pseudo Second Order ◽  
Adsorption Of Co

Reuse of waste from Hami melon (cantaloupes) straws (HS) mingled with polypropylene (PP) ropes is necessary and beneficial to mitigate environmental pollution. The objective of this study was to investigate the characteristics and mechanisms of Cd2+ adsorption on biochars produced by co-pyrolysis of HS-PP with various mixing ratios. N2-sorption, scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), elemental analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravity, and differential thermal gravity (TG/DTG) were applied to evaluate the physicochemical properties of materials. Batch adsorption experiments were carried out for investigating the effects of initial pH, Cd2+ concentration, and adsorption time. It was found that the Langmuir and pseudo-second-order models fitted best for the experimental data, indicating the dominant adsorption of co-pyrolysis biochars is via monolayer adsorption. Biochar derived at 4/1 mixing ratio of HS/PP by weight percentage had the highest adsorption capacity of 108.91 mg·g−1. Based on adsorption isotherm and kinetic analysis in combined with EDS, FTIR, and XRD analysis, it was concluded that the main adsorption mechanism of co-pyrolysis biochar involved the surface adsorption, cation exchange, complexation of Cd2+ with surface functional groups, and chemical precipitation. This study also demonstrates that agricultural wastes to biochar is a sustainable way to circular economy.

scholarly journals A Polypyrrole-Modified Pd-Ag Bimetallic Electrode for the Electrocatalytic Reduction of 4-Chlorophenol

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 931
Author(s):  
Xuefeng Wei ◽  
Laiyuan Zeng ◽  
Weiwei Lu ◽  
Juan Miao ◽  
Ruichang Zhang ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ph Value ◽  
Chemical Deposition ◽  
Electrocatalytic Reduction ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Initial Ph ◽  
Chemical Deposition Method ◽  
Promising Application

A polypyrrole-modified bimetallic electrode composed of Pd-Ag on a Ti substrate (Pd-Ag/PPY/Ti) was successfully prepared via a chemical deposition method, and was applied to the electrocatalytic hydrodechlorination of 4-chlorophenol (4-CP) in aqueous solution. The electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Various influences on the dechlorination efficiency of 4-chlorophenol, including applied current, initial pH value, and temperature, were studied. The dechlorination efficiency of 4-CP reached 94% within 120 min under the optimum conditions, i.e., a dechlorination current of 6 mA, an initial pH of 2.30, and a temperature of 303 K. The apparent activation energy of the dechlorination of 4-CP by the Pd-Ag/PPY/Ti electrode was calculated to be 49.6 kJ/mol. The equivalent conversion rate constant kPd was 0.63 L.gPd−1·min−1, which was higher than the findings presented in comparable literature. Thus, a highly effective bimetallic electrode with promising application prospects and low Pd loading was fabricated.

Framework Fe-Doped Mobil Five (MFI) Zeolites as Highly Active and Stable Fenton-Like Catalysts for Basic Dyes Degradation

2020 ◽  
Vol 20 (3) ◽  
pp. 1520-1529 ◽  
Author(s):  
Senlin Deng ◽  
Guojun Lv ◽  
Yi Zhai ◽  
Zebin Yang ◽  
Yongqiang Zhu ◽  
...  
Keyword(s):  
Ph Value ◽  
Operational Parameters ◽  
One Pot ◽  
Highly Active ◽  
Fe Content ◽  
Basic Dyes ◽  
Initial Ph ◽  
Ft Ir ◽  
The Stability ◽  
Mfi Zeolites

Highly active and stable framework Fe-doped ZSM-5 (f-Fe-ZSM-5) zeolites with different Fe contents, which were synthesized using a facile one-pot hydrothermal method, could effectively resolve the loss of iron element during the catalytic degradation of basic dyes. The successful introduction of Fe species into the framework of ZSM-5 was confirmed by elemental mappings, Fourier transform infrared (FT-IR) spectroscopy and Ultraviolet-visible spectroscopy (UV-vis spectra). The operational parameters, such as Fe content, H2O2 concentration, reaction temperature, types of dyes as well as the stability of the synthesized samples were extensively evaluated. It was demonstrated that the f-Fe(0.10)-ZSM-5 exhibited an efficient catalytic ability and excellent stability even after seven consecutive runs. The degradation efficiency of f-Fe-ZSM-5 for basic dyes was higher than that for acid dye. Therefore, f-Fe-ZSM-5 zeolites may present major potential for the treatment of basic dyes waste water without adjusting the initial pH value.

scholarly journals Utilizing Spent Batteries to Fabricate Ni/ZnO-MnO2 Electrodes for Electrochemical Ammonia Oxidation

2021 ◽  
Author(s):  
Jiachao Yao ◽  
Yu Mei ◽  
Zeyu Wang ◽  
Jun Chen ◽  
Dzmitry Hrynsphan ◽  
...  
Keyword(s):  
Ammonia Oxidation ◽  
Ph Value ◽  
Direct Electron Transfer ◽  
Electrochemical Treatment ◽  
Ammonia Removal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Initial Ph ◽  
A Current ◽  
Mno2 Electrode

Abstract In this work, a novel Ni/ZnO-MnO2 electrode was fabricated by utilizing spent zinc-manganese batteries and then was applied to the electrochemical treatment of ammonia-containing wastewater. The obtained Ni/ZnO-MnO2 electrode was characterized by scanning electron microscopy, X-ray diffraction, and linear scanning voltammetry, suggesting that the fabricated electrode had a flower-like structure and showed high oxygen evolution potential and electrochemical activity. The electrochemical performance of the ZnO-MnO2 electrode in regard to ammonia removal and product selectivity was then investigated with different operating factors (i.e., electrolyte concentration, initial pH value, current density, and Cl− concentration), and the results indicated that the ammonia removal efficiency could reach 100% with a N2 selectivity of 91.8% under optimal conditions. Additionally, the mechanism of ammonia oxidation was proposed by cyclic voltammetry tests and active radical measurements, showing that ammonia was mainly oxidized via direct electron transfer, hydroxyl radicals, and active chlorine. Finally, the ZnO-MnO2 electrode was equipped for the treatment of actual pharmaceutical wastewater, results for which showed that ammonia could be completely removed with a current efficiency of 26.2% and an energy consumption of 52.7 kWh/kg N. Thus, the ZnO-MnO2 electrode prepared by recycling spent batteries is a promising anode for wastewater treatment.

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