Bo Wang, Qiaowen Yang, Ting Li, Sifan Cui, Pengqiang Feng, Xuan Hou
BACKGROUND
Selective catalytic reduction (SCR) can effectively remove NOx from flue gas in a coal-fired power plant. As the core of SCR technology, the catalyst has a limited lifespan. The process of reducing acid leaching and roasting water leaching can efficiently extract vanadium and tungsten from spent SCR catalyst. For vanadium recovery in solution, the traditional vanadium precipitation process by NH4Cl has the disadvantages of consuming high precipitant dosage and producing large amounts of waste water.
RESULTS
This study focused on the vanadium precipitation process using a solution containing vanadium obtained from adopting some steps to handle the spent SCR catalyst. First, melamine was screened out as the vanadium precipitant. Then, the vanadium precipitation conditions were optimized as follows: solution pH value of 1.0, n(C3H6N6)/n(V) = 0.8, 110 °C and 30 min. Under the best precipitation conditions, the vanadium precipitation efficiency of melamine can reach 99.32%. Finally, the mechanisms of vanadium precipitation by NH4Cl and melamine were discussed, respectively.
Abdul Rauf, Mohsin Javed, Muhammad Jahangir, Mehdi Hassan, Anam Tariq, Wajahat Ali, Ali Bahadur, Shahid Iqbal, Sajid Mahmood, Khalid M Alotaibi, Matar Alshalwi
BACKGROUND
In terms of crystalline nanoporous materials, metal–organic frameworks (MOFs) are relatively new. They are self-assembling structures made of organic ligands that serve as linkers between metal centers and metal ions that function as coordination centers. Due to MOFs' high porosity, absence of nonaccessible bulk volume, vast surface areas and variety of pore sizes and topologies, drug delivery via them is becoming more and more common.
RESULTS
Zn-MOF and Zn-MOF@drug were produced using a solvothermal approach in this study and characterized using a variety of methods, including Fourier transform infrared spectroscopy, powder X-ray diffraction and scanning electron microscopy. Utilizing the zone of inhibition and minimum inhibitory concentration approaches, Zn-MOF and Zn-MOF@drug were evaluated for their antibacterial capability against Escherichia coli and Bacillus subtilis, two types of bacteria.
This study reports the preparation of 2-hydroxy-3-(4-(((2-((2-(((E)-4-(2-hydroxy-3-(trimethylammonio)propoxy)-3-methoxybenzylidene)amino)ethyl)amino)ethyl)imino)methyl)-2-methoxyphenoxy)-N,N,N-trimethylpropan-1-aminium (HYM/QA). The adsorbent was employed to extract and concentrate vanadium from its solutions and boiler ash samples.
Results
The impact of initial dosage, pH, reaction time and temperature on the sorption behavior of V(V) was examined. Under optimal conditions (pH 5, 0.08 g dose, 45 min at room temperature), a sorption capacity of 392.25 mg g−1 was achieved. The uptake of V(V) on HYM/QA was effectively reversed using 1 mol L−1 NaOH, regenerating the material. After six cycles of sorption and elution, the sorption capability remained at 91.4% of its initial value. The efficiency and selectivity of HYM/QA toward V5+ ions were assessed using the separation factor parameter, revealing limited interference from heavy metals such as Mn2+, Cr3+, Pb2+, Si4+, Al3+, NO32−, HCO3− and Zn2+. The uptake process of HYM/QA for V(V) conformed to the Langmuir and Dubinin–Radushkevich isotherm models and the pseudo-second-order kinetic model. HYM/QA was characterized by infrared, Brunauer–Emmett–Teller surface area, 1H NMR, 13C NMR and gas chromatography–mass spectrometry analyses, confirming successful preparation. Thermodynamic assessments suggested that the sorption process is endothermic, spontaneous and becoming more favorable with rising temperature.
Anna Carla Ribeiro, Wardleison Martins Moreira, Bruna Bruguer Ferri, Débora dos Federici Santos, Mara Heloisa Neves Olsen Scaliante, Elizabeth de da Costa Neves Fernandes Almeida Duarte, Rosângela Bergamasco
BACKGROUND
Developing robust technologies to remove emerging pollutants from water is urgent since conventional treatments are not technically prepared to remove them. This paper investigated the ibuprofen (IBU) adsorption capacity onto natural zeolite (NZ) and hydrothermally modified zeolite in an acidic medium followed by impregnation with the cationic surfactant cetyltrimethylammonium bromide (CTAB) (MZHT-CTAB). The materials characterization included scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG), N2 adsorption/desorption isotherm (BET), Zeta Potential (ZP), and Point of Zero Charge (pHPZC). The adsorptive capacity studies were carried out by varying the pH solution, a kinetic study at three concentrations (25, 50, and 100 mg L−1), and the contaminant concentration influence (5–100 mg L−1).
RESULTS
The results showed that the MZHT-CTAB obtained both the highest removal efficiency (~ 37%) and the highest adsorption capacity (~ 14 mg g−1) at pH 5.0. The Pseudo Second-Order (PSO) model, which showed the best fit to the experimental data, is significant as it indicates the reliability of our results. The maximum adsorption capacity for the concentration of 100 mg L−1 was 11.93 mg g−1. According to Giles's classification, the isotherm was classified as S-3 type, indicating the competition between the adsorbate and water molecules for the active sites on the adsorbent surface.
Thi Van Anh Nguyen, Thi Thanh Thuy Mai, Thi Binh Phan, Huu Quang Tran, Minh Quy Bui
BACKGROUND
Ferrate(VI), an environmentally friendly oxidant, has recently emerged as one of the most promising chemicals for water and wastewater treatment due to its versatile application as an oxidant, coagulant, and disinfectant. In this paper, the factors affecting the electrosynthesis process of ferrate using ductile iron anode were studied. Besides, the obtained ferrate was used to remove reactive red 195 (RR195).
RESULTS
The optimal ferrate electrochemical synthesis conditions were determined, including 14 mol L−1 NaOH electrolyte solution, a current density of 40 mA cm−2, and electrolysis time of approximately 5–6 h. Furthermore, the kinetics of the ferrate's self-decomposition reaction was also studied at different temperatures. The decomposition process of ferrate in a 14 mol L−1 NaOH environment followed second-order kinetics, with reaction rate constants of 4.70 × 10−9, 7.31 × 10−8, 1.95 × 10−7, and 4.70 × 10−7 (L mol−1 s−1) at temperatures of 4, 10, 20, and 30 °C, respectively. RR195 treatment efficiency by ferrate reached 96.3% in a short time of 3 min at pH 3 with a ferrate/RR195 molar ratio of 30/1.
Wan Nabilah Manan, Wan Nor Roslam Wan Isahak, Zahira Yaakob, Salma Samidin, Khairul Naim Ahmad, Mohd Nor Latif, Ali Faris Aldoghachi, Yun Hin Taufiq-Yap
Background
The quest to manufacture large amounts of syngas to bridge fossil fuels and the renewable energy ecosystem stimulates the creation of efficient and stable heterogeneous catalysts. The NiCeO2 catalysts, synthesized via ultrasonic-assisted citric acid complexation, are highly efficient for the dry reforming of methane (DRM) reaction. Different promoter metals (Zr, La and Sr) were tested for catalytic performance and syngas production. A range of analyses, including X-ray diffraction (XRD), N2 physisorption, H2 temperature-programmed reduction, CO2 temperature-programmed desorption, field emission scanning electron microscopy (FESEM), transmission electron microscopy and X-ray photoelectron spectroscopy, were employed to characterize the physicochemical properties of the catalysts.
Results
XRD results indicated the formation of NiO, CeO2, solid solution ceria–zirconia, perovskite LaNiO3 and SrNiO3 crystalline phases. FESEM results showed the promoted catalysts (Zr, La, Sr) produce large pores to facilitate reactant diffusion, with zirconia specifically creating a spiderweb morphology. At 800 °C, the CH4 and CO2 conversions follow the sequence of NiCeO2 catalyst (CH4 = 54%, CO2 = 45%) < Sr/NiCeO2 (CH4 = 60%, CO2 = 67%) < La/NiCeO2 (CH4 = 85%, CO2 = 84%) < Zr/NiCeO2 (CH4 = 95%, CO2 = 87%). The integration of promoters in DRM catalysts has notably improved carbon formation resistance, as evidenced by the following ranking: Zr/NiCeO2 (5.1 wt%) < commercial catalyst (6.0 wt%) < La/NiCeO2 (7.85 wt%) < Sr/NiCeO2 (10.9 wt%) < NiCeO2 (11.3 wt%).
Bo Yu, Xiaoning Li, Jiao Ma, Han Yan, Ke Lian, Pengfei Shen
BACKGROUND
Arsenic contamination can exert severe detrimental effects on the ecological environment and human health. It can cause acute or chronic poisoning, resulting in cell distortion or cancer when humans come into contact with or consume arsenic-containing water. Adsorption technology is one of the effective methods for arsenic removal. In this study, using attapulgite (ATP) as a support for bimetallic iron–manganese oxides, a series of adsorbents (Fe-Mn/ATP) with different manganese-to-iron molar ratios were prepared via the coprecipitation method. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy mapping, X-ray diffraction and zeta potential measurements were used to analyze the structure and properties of Fe-Mn/ATP. In addition, the adsorption performance of the material for arsenic ions was investigated by static adsorption and dynamic adsorption experiments.
RESULTS
A novel Fe-Mn/ATP adsorbent was prepared using ATP as the raw material and manganese-to-iron molar ratio was 1:3 by coprecipitation at 60 °C for 1 h. The adsorption efficiency of arsenic ions was optimal at an Fe-Mn/ATP dosage of 2 g L−1, pH 4 and a contact time of 10 min, reaching a maximum adsorption capacity of 38.27 mg g−1 at room temperature. The adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model, indicating that arsenic ion adsorption by Fe-Mn/ATP was mainly monolayer chemical adsorption. Furthermore, Fe-Mn/ATP showed a removal rate for arsenic ions of over 80% after four cycles of regeneration, revealing a great potential for practical application.
Leydiane de Oliveira Pereira, Iara do Rosario Guimarães, Luana Pereira Zampiere, Isabela Sales Marques, Stéfany Gonçalves de Moura, Aline Aparecida Caetano, Fabiano Magalhães
BACKGROUND
Photocatalysis is an efficient method for the removal of organic contaminants in wastewater. In this study, different magnetic photocatalysts for the degradation of organic compounds were prepared.
RESULTS
Ti/C/Fe photocatalysts were prepared by supporting TiO2 (20, 40 and 60% w/w) on a carbon/iron oxide (C/Fe) magnetic carrier. Characterization via Raman spectroscopy, X-ray diffractometry, thermal analysis, X-ray fluorescence, scanning electron microscopy and energy-dispersive X-ray spectroscopy/elemental mapping and magnetic property analysis by vibrating-sample magnetometry confirmed the presence of TiO2, Fe3O4, Fe3C and char in the photocatalysts as well as their magnetic properties. The results of specific surface area analysis showed that the C/Fe support had a surface area of 183 m2 g−1 and that this area decreased with an increasing amount of supported TiO2, reaching up to 129 m2 g−1. Diffuse reflectance spectroscopy characterization revealed that the bandgap values obtained for the photocatalysts (Ti/C/Fe) were lower than 3.2 eV. The prepared photocatalysts showed high efficiency in degrading the contaminants Remazol Black (RB5) (99%), paracetamol (77%) and phenol (90%). Recovery and reuse experiments using RB5 showed that after the fourth reaction, the photocatalytic efficiency was reduced by 50%, and the recovery reached up to 70%. Sedimentation kinetics showed that while only 6% of the TiO2 was deposited, up to 89% of the photocatalysts were deposited.
Due to the lower degradation and the potential inhibitory compounds present in slaughterhouse wastewater (SW), its industrial applications are often limited to methane production. This study investigated the combined effect of conductive material such as oat husk-biochar at different concentrations (0, 5, 10, 15, 20, 25 g L−1) and particle sizes (i.e., Powder Biochar (PB) (0.05–0.08 mm) vs. Granular Biochar (GB) (0.8–1.0 mm)) in the methane production, biodegradability, kinetic parameters, methanogenic activity and digestate quality of SW, using a multilevel factorial design.
RESULTS
Experimental results showed that lower concentration (5, 10 g L−1) increased the methane yield up to 35% for PB and between 11 and 13% for GB compared to the control reactor. The total ammoniacal nitrogen concentrations in the digestate declined between 14% and 52% for all biochar dosages and particle sizes. PB improved the specific methanogenic activity of the biomass compared with GB, indicating that PB can support a well-balanced methanogenic community compared with GB inside the digester. The multiple response optimization process computed that 7.5 g L−1 of PB is optimal to increase the methane yield, the COD degradation efficiency and shorten the lag phase. On the other hand, doses higher than 15 g L−1 hinder methane generation.
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