Search

The resource utilization of crop straw, as a part of energy development strategy, is important in term of economy and environmental protection. Based on statistics for agriculture and data, the distribution characteristics, resource utilization, and popularizing demonstration of crop straw in southwest China were comprehensively evaluated. Occurrence of the straw during the last ten years in the Socio-economic Development Region (SEDR) was estimated. On the basis of it, the critical problems during the utilization processes and the multipurpose utilization technologies of crop straw were discussed. Results showed that theoretical straw yield in southwest China in 2015 was 8.2 × 107 t, and corn straw accounted for 54.28% of the total. The order of the straw yield was corn > rice > bean in the three southwest provinces. At present, crop straw is mainly used as soil amendment, fertilizer, fodder, industrial materials, biogas, and power generation. Moreover, the straw fermentation should be also promoted for ecological agriculture. Current progress in straw resource utilization in the innovative demonstration area, namely Liupanshui Agricultural District (LAD), was illuminated. Resource and utilization of crop straw, via biogas production, feedstuff, and returning to field, was about 82% of the total. At the strategic level, regional SEDR system planning should be overall planed in agricultural field, and it is a critical part of the coordinated development of straw utilization. Through the master plan practice of the demonstration area, the suggestions on state modern construction system of agricultural waste were raised.

Phosphorus ore flotation tailings (POFTs) are solid wastes produced in the phosphorus flotation process, and most of the POFTs are directly discharged into the tailing yard without treatment. In this study, modified phosphorus ore flotation tailings (MPOFTs) were synthesized by a hydrothermal chemical modification method as an efficient adsorbent to remove MB. The MPOFTs, the effect of initial MB concentrations, reaction time and pH on the MB characterization, and the adsorption mechanism of MB were studied. The results showed that modification of POFTs had a great BET specific surface area (151.26 m2/g). The maximum adsorption capacity of MPOFTs for MB was 321.5 mg/g at an initial pH of 5.94, the initial MB concentration was 1400 mg/L, and the reaction time was 60 min and 293 K. Moreover, the kinetic adsorption data were well described by both Elovich and pseudosecond order models, while the isotherm data were best fitted by Langmuir model. A thermodynamic analysis indicated that the adsorption process was spontaneous and exothermic adsorption. This study provides a new method for the resource utilization of POFTs.

This study examined simultaneous stabilization and solidification (S/S) of Mn2+ and NH4+-N from electrolytic manganese residue (EMR) using MgO and different phosphate resource. The characteristics of EMR NH4+-N and Mn2+ S/S behavior, S/S mechanisms, leaching test and economic analysis, were investigated. The results show that the S/S efficiency of Mn2+ and NH4+-N could reach 91.58% and 99.98%, respectively, and the pH value is 8.75 when the molar ratio of Mg:P is 3:1 and the dose of PM (MgO and Na3PO4·12H2O) is 8wt%. In this process, Mn2+ could mainly be stabilized in the forms of Mn(H2PO4)2·2H2O, Mn3(PO4)2·3H2O, Mn(OH)2, and MnOOH, and NH4+-N in the form of NH4MgPO4·6H2O. Economic evaluation indicates that using PM process has a lower cost than HPM and HOM process for the S/S of Mn2+ and NH4+-N from EMR at the same stabilization agent dose. Leaching test values of all the measured metals are within the permitted level for the GB8978-1996 test suggested when the dose of PM, HPM and HOM is 8wt%.

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore. In this work, modified electrolytic manganese residue (MEMR) as a high-efficiency adsorbent for the removal of methylene blue (MB) was synthesized via hydrothermal method. The characterizations of MEMR were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherms, and scanning electron microscope. The results showed that with the BET specific surface area of 500.8 m2/g the MEMR reached the maximum adsorption capacity (548.15 m2/g) within 50 min when the pH of initial solution was 6.05 and the initial concentration of MB was 1600 mg/L. The adsorption kinetics and equilibrium isotherms were accurately described by the pseudo-second-order model and Langmuir isotherm, respectively. The FTIR spectra indicated that electrostatic attraction and stacking interaction were the main adsorption mechanisms. Thermodynamic analyses showed that the adsorption of MB on MEMR was a spontaneous and exothermic physisorption process. This study revealed that MEMR can be used as a low cost and eco-friendly potential adsorbent for removing MB from wastewater.

Electrolytic manganese anode slime (EMAS) is a kind of waste produced by anode chambers in the process of electrolytic manganese production. In this study, the surface of EMAS was hydroxylated with EDTA-2Na, and a new adsorbent for removing methylene blue (MB) was obtained. The hydroxylation of EMAS (H-EMAS) was characterized by XRD, XRF, FTIR, BET, SEM and XPS. The results showed that H-EMAS contains many pores and cracks and that the specific surface area of H-EMAS was 53.17 m2/g. The maximum adsorption capacity of H-EMAS for MB was 70.74 mg/g when the initial pH was 6.00, the initial MB concentration was 500 mg/L, the reaction time was 120 min and the reaction temperature was 298 K. Adsorption kinetics and isotherms showed that the adsorption of MB on H-EMAS conformed to pseudosecond-order kinetic model and Langmuir isotherm, respectively. Thermodynamic analysis showed that the adsorption process was a spontaneous and exothermic physical adsorption process. Moreover, H-EMAS adsorbent recycling showed that the adsorption capacity of H-EMAS was 55.35 mg/g after four cycles and that the adsorption efficiency for MB only decreased by 21.75%. This study provides a new method for the resource utilization of EMAS.

Waste printed circuit boards (WPCBs) are identified to be the most complex recycling materials among waste electrical and electronic equipment (WEEE). Slurry electrolysis with acidic system can directly separate and recover copper from WPCBs while current efficiency and purity were generally reduced due to deposition of impurity metals and the hydrogen evolution during recovery process. In ammonia-based system, copper can be selectively extracted and copper (II) ammine complexes generally react with metallic copper to form copper (I) ammine complexes, promoting current efficiency and purity. Therefore, an efficient ammonia-ammonium carbonate slurry electrolysis system is proposed for high purity copper recycling from waste printed circuit boards of mobile phones (WPCB-MPs). The factors affecting copper current efficiency and recovery rate are systematically discussed. These results indicate that appropriate increasing NH3·H2O, (NH4)2CO3, Cu2+, NaCl concentration, solid-to-liquid ratio, current density and reaction time could effectively increase copper recovery rate and current efficiency. The current efficiency and recovery rate of copper are 95.2 and 90.4%, respectively under the optimum test conditions of 20 g/L Cu2+, 0.25 mol/L (NH4)2CO3, 4 mol/L NH3·H2O, 30 g/L solid-to-liquid ratio, 1 mol/L NaCl, 20 mA/cm2, 3 h. Moreover, copper could be recovered at the cathode with a purity of 99.97%. Compared with acidic system, this study provides an efficient approach to recover high purity copper from WPCB-MPs, showing a prospective future for WEEE resource recycling.

Reclaimed copper smelting fly ash (RCA) is generated during the reclaimed purple miscellaneous scrap copper smelting process, and seriously pollutes the environment since it contains Cu, Zn, Pb, Cd and other heavy metals. In this study, leaching and electrowinning process was used for Cu recover from RCA. The effects of RCA and H2SO4 mass ratio, solid–liquid ratio, leaching temperature and time on the leaching efficiencies of Cu, Zn, Pb and Cd were investigated. The effects of current density and electrolysis time on the recovery efficiency of Cu were studied. The results indicated that the leaching efficiency of Cu was 92.52% in the leaching process when the mass ratio of RCA and H2SO4 was 1:0.5, the leaching temperature was 50 °C, the solid–liquid ratio was 40 g/L, and the leaching time was 1 h. All the heavy metal contents in the RCA were decreased via acid leaching, and only the Pb content in the leached RCA was higher than the threshold (GB 5085.3–2007). Moreover, the recovery efficiency of Cu was 94.69%, and the Cu purity in the cathode electrowinning powder was 99.21% in the electrowinning process when the the electrolytic time was 1.5 h and current density was 40 mA/cm2. This study provides a new method for the resource utilization and detoxification of RCA.

Electrolytic manganese anode slime (EMAS) is a solid waste found in the anode chamber during the production of electrolytic manganese metal, which mainly contains high concentration of manganese and other impurities. In EMAS, γ-MnO2 and δ-MnO2 turned into α-MnO2 after calcination, and the oxide can be dissolved by pickling. The results showed that the specific surface area of EMAS increased from 33.11 m2·g− 1 to 93.53 m2·g− 1, and the micropore volume increased from 0.0129 cm3·g− 1 to 0.0362 cm3·g− 1, as well as the specific capacity and the Open Circuit Voltage (OCV) of EMAS were 249.65 mAh·g− 1 and 1.60 V, respectively, under the condition of calcination temperature 400 °C, calcination time 1 h, sulfuric acid 1 mol·L− 1, pickling temperature 25 °C, pickling time 0.5 h, and liquid-to-solid ratio 8:1.

High concentrations of manganese (Mn

Municipal solid waste incineration (MSWI) fly ash contains chlorides, heavy metals, and organic pollutants, which requires appropriate disposal to eliminate this risk. In this study, the effects of agents on heavy metals removal from MSWI fly ash by electric field-enhanced washing were systematically studied. The results show that when these fly ashes were washed at a current density of 35 mA/cm2, polarity switching frequency of 40 Hz, Ethylenediaminetetraacetic acid (EDTA) dosage of 0.5 mol/L, and a pH of 2 for 4 h, almost all of the Cd and Ni could be were removed, with a removal efficiency of 100.00% and 99.59%, respectively. Meanwhile, it also shows a significant effect on Cu and Zn, with a removal efficiency higher than 85%. After washing, the results of the sequential extraction procedure showed that the residual forms of Pb, Cu, Zn, Cd, Ni, and As increased obviously. According to GB5085.3-2007, the toxicity of the treated MSWI fly ash were below their thresholds of 5 and 1 mg/L for Pb and Cd, respectively. Thus, a novel technology for heavy metals removal from MSWI fly ash is proposed.

Waste printed circuit boards (WPCBs) are usually dismantled, crushed, and sorted to WPCB metal-enriched scraps, still containing an amount of non-metallic materials. This research used slurry electrolysis to refine these WPCB metal-enriched scraps and to examine if a standard ionic liquid, [MIm]HSO

Crystalline silicotitanate (CST) was synthesized via a sol-gel hydrothermal method using Na2Si2O3·9H2O and TiCl4 as silicon and titanium sources. The effects of pH, silicon concentration, hydrothermal temperature, and time on the CST synthesis were studied at a fixed molar ratio of silicon:titanium (0.98:1). Pure nano-CST crystals were synthesized at pH = 12.5, silicon concentration of 5 g L-1, 170 °C for 7 days. The average CST particle size was < 100 nm, with a Sr2+/Cs+ distribution coefficient up to 1.9 × 106 mL g-1/9.4 × 103 mL g-1 under the optimum conditions. In addition, nano-CST absorbed Sr2+/Cs+ over a wide pH range. The nano-CST also displayed a much faster equilibrium time, 4 h, as compared with previous studies. Furthermore, nano-CST adsorption of Sr2+/Cs+ followed a Langmuir adsorption model and was consistent with pseudo-second-order kinetics.

As an indispensable part of printed circuit boards (PCBs), central processing unit (CPU) slots contain a significant amount of precious metals which makes economic sense to recycle these materials. Slurry electrolysis is an attractive approach for electronic waste (e-waste) recycling. In this study, the effect of electrolyte reuse on the recovery of metals (Primarily aluminum, nickel, copper, lead, silver, palladium, platinum and gold), from waste CPU slots by slurry electrolysis is discussed in detail. These results show that metal recovery rate, more than 95% for all 13 cycles, was not affected by slurry electrolyte reuse during metal recycling from waste CPU slots, though the reuse of slurry electrolyte greatly impacted the distribution of metals in the anode residues, electrolyte and cathode metal powders. However, slurry electrolysis recovered metals from waste CPU slots and the effect of electrolyte reuse on the recovery of metals from waste CPU slots is discussed for the first time in this study. This could benefit the recycling process since it could improve cathode metal powders recovery rates by approximately 2 times. The acid usage could be significantly reduced by electrolyte reuse when compared to fresh electrolyte. Therefore, electrolyte reuse is demonstrated and slurry electrolysis is a feasible and potentially economically friendly choice for industrial e-waste recycling.

In this study, a new combination method for Mn2+ and NH4+-N removal from electrolytic manganese metal residue (EMMR) using washing and electrolytic oxidation processes was studied. The effects of washing pH, the dosage of sodium hypochlorite, current density, reaction time and reaction temperature on the concentrations of Mn2+ and NH4+-N were investigated. The results showed that the concentrations of NH4+-N and Mn2+ were 6.79 mg/L and 0.05 mg/L, respectively, which were lower than the integrated wastewater discharge standard (GB8978-1996), when the current density was 35 mA/cm2, the sodium hypochlorite dosage was 2%, and the initial pH was 9.5 after reacting for 2 h at 20℃. Mn2+ was mainly removed in the forms of MnO2, Mn2O3, MnOOH and Mn3O4. NH4+-N was mainly oxidised to N2. This study provides a new harmless treatment technology for EMMR.

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue leachate (EMRL) have seriously polluted the environment. In this study, electric field and phosphorus ore flotation tailings (POFTs) were used for Mn2+ and NH4+-N removal in EMRL firstly. The effects of the liquid acid ratios, reaction temperature, current density, initial pH and stable pH of the solution, characteristics of EMRL and POFTs, and removal mechanism of NH4+-N and Mn2+ were investigated. The results indicated that an electric field enhanced the leaching of POFTs and promoted the adsorption and precipitation of Mn2+ and NH4+-N. The concentrations of Mn2+, NH4+-N, PO43− and F− in EMRL were 0.12 mg/L, 9.2 mg/L, 0.09 mg/L, and 0.24 mg/L, respectively, which were within the permitted level for the integrated wastewater discharge standard (GB8978-1996) after adjusting the second stable pH to 10.0. Mn2+ was mostly remove in the form of Mn(OH)2, MnOOH, Mn5(OH)4(PO4)2 and MnO2. NH4+-N was mostly remove as NH4MgPO4·6H2O. The phosphate precipitation obtained could be used as market fertilizer. This study provided a new research idea for EMRL harmless disposal and POFTs resource utilization.

Waste Electrical and Electronic Equipment (WEEE) contain toxic metals and organic compounds, posing significant threats to human health and environmental quality. The risks vary according to equipment types and components that are influenced by innovations in technical configuration and regulatory policy. To disentangle the relative impacts of these influences in protecting health and environment, we investigated 13 WEEE and 14 components using a life cycle impact assessment procedure. Additionally, we analyzed Waste Mobile Phones (WMPs) and Waste Printed Circuit Boards (WPCBs) from computers manufactured between 2002 and 2010 to identify trends of toxic chemicals and potential adverse impacts associated with technological configurations and regulatory policies. The results show that, among WEEE, Cathode Ray Tube TV presented the highest carcinogenicity and non-carcinogenicity toxicity potential. Waste Air Conditioner posed the highest potential for ecotoxicity. Among electronic components, Waste Organic Light Emitting Diode displays posed the highest potential risk for carcinogenesis, whereas WPCBs from laptop computers posed the highest potential risk for non-cancer diseases. Solid State Drives posed the highest risks for ecotoxicity. Chromium was associated with risk of carcinogenesis and non-cancer diseases; whereas Al and Fe posed the highest potential for ecotoxicological impacts. During the period covered by the study, innovations in technological configurations and regulatory policies demonstrably reduced the potential toxicity risks posed by E-waste, attributable to reduction in the concentrations of toxic organic chemicals in WMPs/WPCBs. These results advance current understanding of strategies to reduce the risks posed by WEEE through coordination of technological innovations and regulatory policies.

In this study, we employed an innovative method to fractionally reduce high concentrations of nickel (Ni2+), PO43−, total phosphorus (TP), chemical oxygen demand (COD), and ammonia nitrogen (NH4+-N) from printed-circuit-board nickel plating (PCBNP) wastewater, a hazardous waste. The removal efficiencies of Ni2+, PO43−, TP, COD, and NH4+-N from PCBNP wastewater using electrochemical deposition, CaO-enabled complex dissociation, and Fenton oxidation as well as the removal mechanism were studied. The results revealed that Ni2+ was removed in the process of electrochemical precipitation; NH4+-N and fractions of TP and COD were removed in the complex dissociation process using CaO; and COD and TP were removed in the Fenton process. The removal efficiencies of Ni2+, PO43−, TP, COD, and NH4+-N were respectively 99.99%, 99.97%, 99.70%, 98.16%, respectively, and 99.43%, when the current density was 25 mA/cm2, CaO dosage was 12.5 wt%, and m(FeSO4·7H2O):m(H2O2) was 1:8. Ni2+ was mainly recovered as Ni-P during the electrochemical deposition process, whereas NH4+-N was removed during the dissociation process using CaO. COD was oxidized to CO2 and H2O, and PO43−, phosphite (HPO32−), and hypophosphite (H2PO2−) were mainly removed as FePO4 via the Fenton oxidation process. Adjust the pH to 6.0 by NaOH after Fenton treated effluent. An economic evaluation determined that the cost of treatment of PCBNP wastewater was 136.604 $·m−3. Moreover, the treated wastewater could be discharged directly to an industrial park. This method provides a novel approach for the treatment of PCBNP wastewater.

Ammonia and manganese were simultaneously removed from electrolytic metal manganese residue leachate using phosphate salt. The influence of different N:P ratios and pH were investigated. Phase transition and decomposing behavior of precipitates and the characterization of the precipitates pyrolysis were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscope. In the laboratory experiment, under the condition of 1:1.15 N:P ratio and 9.5 pH value, removal efficiencies of ammonia and manganese from the residue leachate were achieved 95.0% and 99.9%, respectively, and remaining concentration of orthophosphate was as low as 12 mg L−1. In the process, manganese was first removed as Mn3(PO4)2·7H2O, and then ammonia was removed as NH4MgPO4·6H2O. In addition, MgNaPO4, MgHPO4, Mg2P2O7, Na3PO4 and MnO2 were generated during precipitate pyrolysis process, and the ammonia removal efficiency decreased from 84.0% in the first cycle to 66.0% in the fifth, and manganese removal efficiency was approximately 99.0%. Economic evaluation shows that recycling the precipitates for three times could save 68.4% cost on average, compared to the use of pure chemicals.

In this study, P-LGMgO (low-grade MgO and NaH 2 PO 4 ·2H 2 O), P-CaO (CaO and NaH 2 PO 4 ·2H 2 O), and P-MgCa (low-grade MgO, CaO and NaH 2 PO 4 ·2H 2 O) were used for the solidification/stabilization (S/S) of electrolytic manganese residue (EMR). Relevant characteristics such as ammonia nitrogen and manganese stabilization behavior, unconfined compressive strength (UCS), probable S/S mechanisms, and EMR leaching test were investigated. The results demonstrate that using P-LGMgO had higher stabilization efficiency than P-CaO and P-MgCa for the S/S of EMR at the same stabilization agent dose. The stabilization efficiency of ammonia nitrogen and manganese in the EMR were 84.0% and 99.9%, respectively, and the UCS of EMR was 5.1 MPa using P-LGMgO process after curing for 28 days when the molar ratio of Mg:P was 5:1 and dose of stabilization agent was 12 wt%. In this process, ammonia nitrogen was stabilized by struvite (NH 4 MgPO 4 ·6H 2 O), and manganese by bermanite (Mn 3 (PO 4 ) 2 (OH) 2 ·4H 2 O) and pyrochroite (Mn(OH) 2 ). The leaching test results show that the values of all the measured metals on the 28th day were within the permitted level for the GB8978-1996 test suggested by China’s environmental protection law and the concentration of ammonia nitrogen can be reduced from 504.0 mg L −1 to 76.6 mg L −1 .

High-valent manganese was hard to be extracted from electrolytic manganese residues. To strengthen the extraction of Mn, electrochemical extraction method was investigated in this work. The mechanisms of the electrochemical extraction were examined along with the electrochemical performance of the reaction system via X-ray diffraction, scanning electron microscopy, X-ray Fluorescence, and BET. Results show that high-valent manganese can be reduced effectively under an electric field. The extraction efficiencyof manganese reached 96.2% under the optimum conditions of current density 25 mA/cm 2 , 9.2 wt% H 2 SO 4 , solid-to-liquid ratio of 1:5, room temperature, 1:1.0 M ratio of Mn to Fe 2 + and 60 min extraction. The extraction efficiency of manganese is 51.8% higher than that attained under the same conditions without an electric field and Fe 2 + . Meanwhile, the manganese content in residue decreased from 2.34% to 0.09%.

In this study, an improved process for leaching manganese from electrolytic manganese residue (EMR) by electro-reduction was developed. The mechanisms of the electro-reduction leaching were investigated through X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and Brunauer Emmett Teller. The results show that the electric field could change the surface charge distribution of EMR particles, and the high-valent manganese can be reduced by electric field. The leaching efficient of manganese reached 84.1% under the optimal leaching condition: 9.2 wt% H2SO4, current density of 25 mA/cm2, solid-to-liquid ratio of 1:5, and leaching time for 1 h. It is 37.9% higher than that attained without an electric field. Meanwhile, the manganese content in EMR decreased from 2.57% to 0.48%.

Ammonia nitrogen- and manganese-contaminated water poses a considerable threat on the safety of water resources. In this work, pulse current (PC) electrolysis, a novel process, was developed to recover manganese and remove ammonia nitrogen from simulation wastewater simultaneously. Accordingly, the parameters of pulse electrolysis, and technological conditions, including temperature, initial pH, and concentration of addition NaCl, were investigated. The results showed that the concentration of manganese in simulation wastewater could be reduced from 160 mg L−1 to 0.2 mg L−1, meanwhile, ammonia nitrogen could be removed from 80 mg L−1 to 0.1 mg L−1 for 2.5 h PC electrolysis at 30 mA cm−2, 1000 Hz, and duty cycle 50% where settled with Ti/SnO2 IrO2 RuO2 electrodes, when the initial pH was 10.0 and NaCl addition was 0.008 mol L−1 at room temperature. Moreover, XRD and SEM analysis showed that manganese dioxide was deposited on the anode, and manganese in simulation wastewater was mainly recovered in the form of manganese dioxide.

In this work, nitrite was developed to simultaneously remove manganese and ammonia nitrogen from wastewater by the electrochemical method. The characteristics of electrolytic reaction were observed via cyclic voltammograms. Moreover, the mole ratio of nitrite and ammonia nitrogen, voltage, and initial pH value, which affected the removal efficiency of ammonia nitrogen and manganese, were investigated. The results showed that the concentration of ammonia nitrogen in wastewater could be reduced from 120.2 to 6.0 mg L−1, and manganese could be simultaneously removed from 302.4 to 1.5 mg L−1 at initial pH of 8.0, the mole ratios of nitrite and ammonia nitrogen of 1.5:1, and voltage of 20 V direct current electrolysis for 4.0 h. XRD analysis showed that manganese dioxide was deposited on the anode, and manganese was mainly removed in the form of manganese hydroxide precipitation in the cathode chamber.

Waste lithium-ion batteries (LIBs) contain cobalt, lithium, and other valuable materials, which attracts the attention of a large number of researchers. Taking effective measures not only reduced environmental pollution but also maximizes economic benefits. In this work, an effective and environmental-friendly approach for leaching cobalt and lithium from LIBs by a green glycine was developed. The leaching rates of Co and Li were respectively 97.07% and 90.95% (300 g/L glycine, 10% H2O2, solid/IL ratio of 1:100, 353 K, 7 h). The results of leaching kinetics show that the leaching process is controlled by interfacial chemical reactions, and the activation energy of Co and Li is respectively 78.57 kJ mol−1 and 56.20 kJ mol−1. In addition, scanning electron microscopy (SEM) and x-ray diffraction (XRD) were applied to analyze the morphology and phase composition of waste LIBs before and after leaching, and the XRD results prove the leaching of LiCoO2 since its peak intensity decreased greatly, which indicated the decomposed of LiCoO2 after leaching. Therefore, the use of glycine, a green extractant, does not only result in a higher leaching efficiency, but also reduces the use of inorganic acids, providing a novel approach for the green recovery of waste LIBs in the future.

Electrolytic manganese residue (EMR) is a solid waste remained in filters after using sulfuric acid to leaching manganese carbonate ore. EMR contains high concentration of soluble manganese (Mn2+) and ammonia nitrogen (NH4+-N), which seriously pollutes the environment. In this study, a low cost of phosphate based binder for Mn2+ and NH4+-N stabilization in EMR by low grade-MgO (LG-MgO) and superphosphate was studied. The effects of different types of stabilizing agent on the concentrations of NH4+-N and Mn2+, the pH of the EMR leaching solution, stabilizing mechanisms of NH4+-N and Mn2+, leaching test and economic analysis were investigated. The results shown that the pH of the EMR leaching solution was 8.07, and the concentration of Mn2+ was 1.58 mg/L, both of which met the integrated wastewater discharge standard (GB8978-1996), as well as the concentration of NH4+-N decreased from 523.46 mg/L to 32 mg/L, when 4.5 wt.% LG-MgO and 8 wt.% superphosphate dosage were simultaneously used for the stabilization of EMR for 50 d Mn2+ and NH4+-N were mainly stabilized by Mn3(PO4)2·2H2O, MnOOH, Mn3O4, Mn(H2PO4)2·2H2O and NH4MgPO4·6H2O. Economic evaluation revealed that the treatment cost of EMR was $ 11.89/t. This study provides a low-cost materials for NH4+-N and Mn2+ stabilization in EMR.

The metal recycling processes in the waste printed circuit boards (WPCBs) are mainly pyrometallurgy and hydrometallurgy, whereas hydrometallurgy is considered as an efficient but less environmentally friendly process. In this study, a green amino acid, glycine, was used to replace traditional inorganic acids to extract Cu from WPCBs by investigating the effects of temperature, H2O2 volume, solid–liquid ratio and glycine concentration on Cu leaching efficiency. The kinetics and thermodynamics of the leaching process were also studied. The maximum leaching efficiency is up to 94.08% when the temperature is 30 °C, initial H2O2 volume is 10%, the solid–liquid ratio is 1:100 and the initial glycine concentration is 1 mol/L. After leaching, sky blue crystal, cupric-glycinate, could obtain by adding absolute ethyl alcohol. The leaching process is controlled by diffusion and chemical reactions. All these results show that the green glycine could successfully replace traditional inorganic acids to extract Cu from WPCBs, providing a feasible and perspective future for industrial application.

In this study, a new electrochemical method was used to simultaneously efficient removal of Mn2+ and NH4+-N in wastewater with Cu plate as cathode. The effects of various reaction parameters on the concentrations of Mn2+, NH4+-N and by-products (NO3−-N and NO2−-N, free chlorine and residual chlorine), as well as the removal mechanism were investigated. The results showed that the removal efficiencies of Mn2+ and NH4+-N were 99.1% and 92.9%, and the concentrations of NO3−-N, NO2−-N, free chlorine and residue chlorine were 0.73 mg/L, 0.15 mg/L, 0.13 mg/L and 0.63 mg/L reacting for 3 h at room temperature, respectively, when the current density was 10 mA/cm2, the mass ratio of ClO− and Cl− was 1:1, the initial pH was 9. The concentrations of Mn2+, NH4+-N and by-products in wastewater met the integrated wastewater discharge standard (GB8978-1996). In addition, spherical manganese oxide was deposited on the anode plate, and spherical manganese oxide collapsed over electrolysis time. Manganese was mainly removed in the form of MnO, Mn(OH)2 and MnO2. NH4+-N was mainly oxidized to N2. Economic evalution revealed that the treatment cost was 2.93 $/m3.

Electrolytic manganese residue (EMR) contains a lot of manganese (Mn2+) and ammonia nitrogen (NH4+-N), which can cause environmental pollution. In this study, surfactant and anode iron plate were used to synergistically enhance NH4+-N and Mn2+ leaching from EMR. The Characteristics of EMR, Mn2+ and NH4+-N leaching mechanism, and the leaching test were systematically studied. The results showed that the leaching efficiencies of Mn2+ and NH4+-N were 89.4% and 65.9%, respectively, when the current density was 20 mA/cm2 and iron as the anode plate, the mass of H2SO4 was 13 wt%, solid-to-liquid ratio of 1:5 at 20 °C reacting for 120 min. In addition, when the surfactant concentration of tetradecyl trimethylammonium chloride (TTC) was 100 mg/L, the leaching efficiency of Mn2+ and NH4+-N in EMR respectively increased from 89.4% to 97.1% and from 65.9% to 98.4% by adding electric field. The leaching efficiencies of Mn2+ and NH4+-N were 28.5% and 93.7%, respectively, which was higher than that attained under the same condition without an electric field and TTC surfactant. Meanwhile, electric field changed the movement and charge distribution of charged particles on the surface of SiO2 and CaSO4·2H2O particles and released soluble compound salt containing Mn2+ and NH4+-N. TTC surfactant also improved the hydrophilic and hydrophobic properties of the EMR surface and promoted the wetting ability of the particles and the leaching of Mn2+ and NH4+-N. This study shows that TTC surfactant and anode iron plate can enhance NH4+-N and Mn2+leaching from EMR.

Effective recycling waste lithium-ion batteries (LIBs) are of great economic and environmental benefits. This study proposes a novel and efficient ammonia leaching method for recovering Co and Li from waste LIBs. This method yields a Co and Li leaching rate of 91.16% and 97.57%, respectively, under the optimal conditions (NH3·H2O 120 g/L, NH4HCO3 75 g/L, n (Na2SO3): n (Co) = 2:1, 353 K, 240 min). Leaching kinetics also show that the speed-limiting step in this process is the interfacial chemical reaction, and the activation energy of Co and Li is 58.45 kJ mol−1 and 50.05 kJ mol−1, respectively. Moreover, scanning electron microscopy (SEM), energy dispersion spectrum (EDS), and x-ray diffraction (XRD) results indicate that the morphology of waste LIB powder are irregular granular and lamellar. Under the optimal condition, however, the leaching residues are scattered particles at a smaller size and the as formed MnCO3 particles are smooth with a uniform cubic structure. Besides, MnCO3 and graphite in the leaching residues can be separated and recovered. After that MnCO3 was further calcined to Mn3O4, a precursor for the production of new LIBs. Hence, a new and effective way for spent LIBs circular recycling is put forward, providing another choice for spent LIBs recycling industry.

Electrolytic manganese residue (EMR) contains large quantities of manganese (Mn

This study examined simultaneous stabilization and solidification (S/S) of Mn

Electrolytic manganese residue (EMR) is a solid waste generated in filters after sulfuric acid leaching of manganese carbonate ore, which contains manganese, ammonia nitrogen and heavy metals that cause damage to environment. In fact, leaching and recovery of manganese and ammonia nitrogen from EMR is the key to the harmless treatment and resource utilization of EMR. In this study, electric field was applied to leach manganese and ammonia nitrogen from EMR. In addition, carbonate precipitation and struvite precipitation methods were used to recover manganese and ammonia nitrogen from leaching solution. The results showed that the leaching efficiencies of manganese and ammonia nitrogen were 88.07% and 91.50%, respectively, when the current density was 35 mA/cm2, the mass of H2SO4 and H2O2 were 9.15 wt% and 3.33 wt%, solid-liquid ratio was 1:5 at temperature of 40 °C leached for 120 min. All heavy metals content in leached EMR except Ni and Cd were below national standard (GB 15618–2018) by electric field enhanced leaching. Meanwhile, manganese and ammonia nitrogen in leaching solution were fractional recovered by MnCO3 and struvite, and the recovery efficiency of manganese and ammonia nitrogen was 98.6% and 98.0%, respectively. This study provides a direction for the effective harmless treatment and resource utilization of EMR.

For optimizing the reaction conditions of 2-methyl-6-ethylaniline (MEA) degradation catalyzed by horseradish peroxidase (HRP), a response surface methodology with three factors and three levels was used in this research to establish a regression model, a ternary quadratic polynomial, in order to analyze temperature, H2O2 concentration and pH effects on MEA removal efficiency. The results showed that the regression model was significant (p &lt, 0.0001), fitted well with experimental data and had a high degree of reliability and accuracy, and the data were reasonable with low errors. By analyzing interactions and solving the regression model, the maximum MEA removal efficiency was 97.90%, and the optimal conditions were defined as follows: pH 5.02, H2O2 concentration 13.41mM, and temperature 30.95 &deg, C. Under the optimal conditions, the average MEA removal efficiency obtained from the experiments was 97.56%. This research can provide reference for the treatment of actual acetochlor industrial wastewater.

Removal of hexavalent chromium had attracted much attention as it is a hazardous contaminant. An electrocoagulation-like technology electro-reduction was applied. The chromium (VI) in the wastewater was reduced to chromium (III) by the electron supplied by electricity power and Fe2+, formed from corrosion of steel electrodes in acidic conditions. The mechanism and parameters affecting the reaction were investigated. The results optimized by response surface methodology indicated that the influence of single factor on the reduction efficiency followed the order: A: dosage of H2SO4 &gt, C: reaction time &gt, D: reaction temperature &gt, B: current intensity. The reduction efficiency was hardly affected by current intensity, while it was increased with the increasing of reaction time and acid concentration. The reducing agent, Fe2+ an and extra free electron, acted as a reducing agent and could easily reduce hexavalent chromium to trivalent chromium at high temperatures in an acidic medium.

The objective of this work was the immobilization of soluble manganese (Mn) and ammonium nitrogen (NH4 +-N) leached from electrolytic manganese residue (EMR). Immobilization of Mn was investigated via carbonation using carbon dioxide (CO2) and alkaline additives. NH4 +-N immobilization was evaluated via struvite precipitation using magnesium and phosphate sources. Results indicated that the immobilization efficiency of Mn using CO2 and quicklime (CaO) was higher than using CO2 and sodium hydroxide (NaOH). This higher efficiency was likely due to the slower release of OH− during CaO hydrolysis. The immobilization efficiency of Mn was >99.99 % at the CaO:EMR mass ratio of 0.05:1 for 20-min reaction time. The struvite precipitation of NH4 +-N was conducted in the carbonated EMR slurry and the immobilization efficiency was 89 % using MgCl2 · 6H2O + Na3PO4 · 12H2O at the Mg:P:N molar ratio of 1.5:1.5:1 for 90-min reaction time. A leaching test showed that the concentrations of Mn and NH4 +-N in the filtrate of the treated EMR were 0.2 and 9 mg/L, respectively. The combined immobilization of Mn and NH4 +-N was an effective pretreatment method in the harmless treatment of the EMR.

Leaching tests of electrolytic manganese residue (EMR) indicated that high contents of soluble manganese and ammonia-nitrogen posed a high environmental risk. This work reports the results of simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese by air under calcium oxide assist. The ammonia-nitrogen stripping rate increased with the dosage of CaO, the air flow rate and the temperature of EMR slurry. Stripped ammonia-nitrogen was absorbed by a solution of sulfuric acid and formed soluble (NH4)2SO4 and (NH4)3H(SO4)3. The major parameters that effected soluble manganese precipitation were the dosage of added CaO and the slurry temperature. Considering these two aspects, the efficient operation conditions should be conducted with 8 wt.% added CaO, 60°C, 800 mL min(-1) air flow rate and 60-min reaction time. Under these conditions 99.99% of the soluble manganese was precipitated as Mn3O4, which was confirmed by XRD and SEM-EDS analyses. In addition, the stripping rate of ammonia-nitrogen was 99.73%. Leaching tests showed the leached toxic substances concentrations of the treated EMR met the integrated wastewater discharge standard of China (GB8978-1996).

The water–gas shift reaction (WGSR) promoted by several Pt-based catalysts Pt3M (M = Pt, Cu, Mo, Ni, Rh) has been investigated with density functional theory calculations in the present work. The reaction mechanism is explored along an associative carboxylate-formate mechanism. The catalytic cycle processes, in all cases, involve three sequential elementary steps: the rupture of the O–H bond in H2O, the formation of OCOH, and the formate dissociation and CO2 desorption. According to thermodynamics results, the energy barriers in path I on all clusters are lower than those of in path II and path III, indicating that WGSR prefers to occur when H2O and CO2 adsorb on the same Pt atom. Pt3Cu and Pt3Rh bimetallic clusters exhibit superior catalytic activity for WGS reaction among all those investigated clusters. The present theoretical study enriches our understanding of the WGSR promoted by Pt-based catalysts.

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H2SO4 and Na2SO4 as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.