Rapid electrodeposition of Cu nanoparticle film on Ni foam as an integrated 3D free-standing electrode for non-invasive and non-enzymatic creatinine sensing.

High cost, inherent destabilization, and intricate fixing of enzyme molecules are the main drawbacks of enzyme-based creatinine sensors. The design of a low-cost, stabilizable, and enzyme-free creatinine sensing probe is essential to address these limitations. In this work, an integrated three-dimensional (3D) free-standing electrode was designed to serve as a non-enzymatic creatinine sensing platform and was fabricated by rapid electrodeposition of a dense copper nanoparticle film on nickel foam (Cu NP film/NF). This low-cost, stable, easy-to-fabricate, and binder-free Cu NP film/NF electrode has abundant active sites and excellent electrochemical performance. Cyclic voltammetry measurements show a wide linear range (0.25-24 mM), low detection limit (0.17 mM), and high sensitivity (306 µA mM-1 cm-2). The developed sensor shows high recovery of creatinine concentration in real urine. Besides, it has better specificity, reproducibility, and robustness in detecting creatinine. These excellent results suggest that a non-enzymatic creatinine sensor based on an integrated 3D free-standing Cu NP film/NF electrode has good potential for non-invasive detection of urinary creatinine.

Deep removal of phosphate from electroplating wastewater using novel Fe-MOF loaded chitosan hydrogel beads.

Since the electroplating industry is springing up, effective control of phosphate has attracted global concerns. In this study, a novel biosorbent (MIL-88@CS-HDG) was synthesized by loading a kind of Fe-based metal organic framework called MIL-88 into chitosan hydrogel beads and applied in deep treatment of phosphate removal in electroplating wastewater. The adsorption capacities of H2PO4- on MIL-88@CS-HDG could reach 1.1 mmol/g (corresponding to 34.1 mg P/g and 106.7 mg H2PO4-/g), which was 2.65% higher than that on single MOF powders and chitosan hydrogel beads. The H2PO4- adsorption was well described by the Freundlich isotherm model. Over 90% H2PO4- could be adsorbed at contact time of 3 h. It could keep high adsorption capacity in the pH range from 2 to 7, which had a wider pH range of application compared with pure MIL-88. Only NO3- and SO42- limited the adsorption with the reduction rate of 11.42% and 23.23%, proving it tolerated most common co-existing ions. More than 92% of phosphorus could be recovered using NaOH and NaNO3. Electrostatic attraction between Fe core and phosphorus in MIL-88@CS-HDG and ion exchange played the dominant role. The recovered MIL-88@CS-HDG remained stable and applicable in the treatment process of real electroplating wastewater even after six adsorption-regeneration cycles. Based on the removal properties and superb regenerability, MIL-88@CS-HDG is potentially applicable to practical production.

Transformation behavior of heavy metal during Co-thermal treatment of hazardous waste incineration fly ash and slag/electroplating sludge.

In this study, the behavior of heavy metal transformation during the co-thermal treatment of hazardous waste incineration fly ash (HWIFA) and Fe-containing hazardous waste (including hazardous waste incineration bottom slag (HWIBS) and electroplating sludge (ES)) was investigated. The findings demonstrated that such a treatment effectively reduced the static leaching toxicity of Cr and Pb. Moreover, when the treatment temperature exceeded 1000 °C, the co-thermal treated sample exhibited low concentrations of dynamically leached Cr, Pb, and Zn, indicating that these heavy metals were successful detoxified. Thermodynamic analyses and phase transformation results suggested that the formation of spinel and the gradual disappearance of chromium dioxide in the presence of Fe-containing hazardous wastes contributed to the solidification of chromium. Additionally, the efficient detoxification of Pb and Zn was attributed to their volatilization and entry into the liquid phase during the co-thermal treatment process. Therefore, this study sets an excellent example of the co-thermal treatment of hazardous wastes and the control of heavy metal pollution during the treatment process.

Near-complete recycling of real mix electroplating sludge as valuable metals via Fe/Cr co-crystallization and stepwise extraction route.

In electroplating sludge, iron (Fe) and aluminum (Al) are common impurities that need to be separated before recycling valuable heavy metals. However, the traditional Fe/Al separation process often leads to significant losses of heavy metals. To address this issue, a new approach was developed to sequentially separate Fe/Al and recycle chromium (Cr) and nickel (Ni) from real electroplating sludge. The sludge contained 4.5% Cr, 1.2% Al, 1.1% Ni, and 14.6% Fe. Initially, the sludge was completely dissolved in a mixture of hydrochloric and nitric acids. The resulting acid solution was then heated to 160 °C for 10 h with the addition of saccharose. This hydrothermal treatment led to the hydrolysis and crystallization of 98.3% of Fe, 31.8% of Cr, 1.1% of Al, and 4.9% of Ni, forming akaganeite-bearing particles. It was observed that the excessive amount of saccharose also improved the removal of Cr, Al, and Ni, but decreased the removal of Fe. After the hydrothermal treatment, the remaining supernatant was adjusted to different pH levels (1.9, 2.9, and 4.5, respectively), and then Al, Cr, and Ni were stepwise extracted using di-(2-ethylhexyl) phosphate acid (P204). The recycling efficiencies achieved were 97.4% for Al, 61.2% for Cr, and 89.3% for Ni. This approach provides a promising method for the stepwise separation of Fe/Al and the recycling of heavy metals from electroplating sludge.

Treatment of electroplating wastewater using electrocoagulation and integrated membrane.

Electroplating wastewater contains heavy metal ions and organic matter. These contaminants not only endanger the environment but also pose risks to human health. Despite the development of various treatment processes such as chemical precipitation MBR, electrocoagulation (EC) ceramic membrane (CM), coagulation ultrafiltration (UF) reverse osmosis (RO), and CM RO. These methods are only effective for low concentrations of heavy metals and struggle with high concentrations. To address the challenge of treating electroplating wastewater with high heavy metal content, this study focuses on the wastewater from Dongfang Aviation Machinery Processing Plant. It introduces an EC and integrated membrane (IM) treatment process for electroplating wastewater. The IM comprises microfiltration (MF) membrane, nanofiltration (NF) membrane, and RO membrane. Results indicated that under specific conditions, such as a pH of 8, current density of 5 A/dm2, electrode plate spacing of 2 cm, 35 min of electrolysis time, and influent pH of 10 for the IM, removal rates of Zn2+, Cu2+, Ni2+, and TCr in the wastewater exceeded 99%. The removal rates of chemical oxygen demand (COD), suspended solids (SS), total phosphorus (TP), total nitrogen (TN), and petroleum in wastewater exceed 97%. Following a continuous cleaning process, the membrane flux can consistently recover to over 94.3%.

Industrial effluents and N-nitrosamines in karst aquatic systems: a study on distribution and ecological implications.

The discharge of electroplating wastewater, containing high concentrations of N-nitrosamines, poses significant risks to human health and aquatic ecosystems. Karst aquatic environment is easily impacted by N-nitrosamines due to the fragile surface ecosystem. However, it's still unclear in understanding N-nitrosamine transformation in karst water systems. To explore the response and transport of nine N-nitrosamines in electroplating effluent within both karst surface water and groundwater, different river and groundwater samples were collected from both the upper and lower reaches of the effluent discharge areas in a typical karst industrial catchment in Southwest China. Results showed that the total average concentrations of N-nitrosamines (∑NAs) in electroplating effluent (1800 ng/L) was significantly higher than that in the receiving river water (130 ng/L) and groundwater (70 ng/L). The dynamic nature of karst aquifers resulted in comparable average concentrations of ∑NAs in groundwater (70 ng/L) and river water (79 ng/L) at this catchment. Based on the principal component analysis and multiple linear regression analysis, the electroplating effluent contributed 89% and 53% of N-nitrosamines to the river water and groundwater, respectively. The results based on the species sensitivity distribution model revealed N-nitrosodibutylamine as a particularly toxic compound to aquatic organisms. Furthermore, the average N-nitrosamine carcinogenic risk was significantly higher in lower groundwater reaches compared to upper reaches. This study represents a pioneering effort in considering specific N-nitrosamine properties in evaluating their toxicity and constructing species sensitivity curves. It underscores the significance of electroplating effluent as a primary N-nitrosamine source in aquatic environments, emphasizing their swift dissemination and significant accumulation in karst groundwater.

Chromoionophoric probe-anchored mesoporous silica nanospheres for rapid and reliable naked-eye detection of Ni(II) ions in petroleum products and removal from electroplating wastewater.

This paper presents the expansion of an optical, chemical sensor that can rapidly and reliably detect, quantify, and remove Ni(II) ions in oil products and electroplating wastewater sources. The sensor is based on mesoporous silica nanospheres (MSNs) that have an extraordinary surface area, uniform surface morphology, and capacious porosity, making them an excellent substrate for the anchoring of the chromoionophoic probe,3'-{(1E,1' E)-[(4-chloro-1,2 phenylene)bis (azaneylylidene)]-bis(methaneylylidene)}bis(2-hydroxybenzoic acid) (CPAMHP). The CPAMHP probe is highly selective and sensitive to Ni(II), enabling it to be used in naked-eye colorimetric recognition of Ni(II) ions. The MSNs provide several accessible exhibited sites for uniform anchoring of CPAMHP probe molecules, making it a viable chemical sensor even with the use of naked-eye sensing. The surface characters and structural analysis of the MSNs and CPAMHP sensor samples were examined using various techniques. The CPAMHP probe-anchored MSNs exhibit a clear and vivid color shift from pale yellow to green upon exposure to various concentrations of Ni(II) ions, with a reaction time down to approximately 1 minute. Furthermore, the MSNs can serve as a base to retrieve extremely trace amounts of Ni(II) ions, making the CPAMHP sensor a dual-functional device. The calculated limit of recognition for Ni(II) ions using the fabricated CPAMHP sensor samples is 0.318 ppb (5.43 × 10-9 M). The results suggest that the proposed sensor is a promising tool for the sensitive and reliable detection of Ni(II) ions in petroleum products and for removing Ni(II) ions in electroplating wastewater; the data indicate an excellent removal of Ni (II) up to 96.8%, highlighting the high accuracy and precision of our CPAMHP sensor.

Electrodeposition of paracetamol oxide for intelligent portable ratiometric detection of nicotine and ethyl vanillin ß-D-glucoside.

Herein, the electrodeposition of paracetamol oxide (PA ox) for the intelligent portable ratiometric detection of nicotine (NIC) and ethyl vanillin ß-D-glucoside (EVG) is reported. PA ox electrodeposited on a screen-printed carbon electrode (SPCE) was used as a new fixed state ratiometric reference probe. A portable electrochemical workstation combined with a smart phone was applied as an intelligent portable electrochemical sensing platform. The sensor was studied by scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FT-IR), ultraviolet-visible spectrophotometry (UV-vis), theoretical calculation, chronoamperometry, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). Under optimized conditions, the detection range of NIC is 10-200 µmol L-1, and the detection limit is 0.256 µmol L-1. The detection range of EVG was 10-180 µmol L-1, and the detection limit was 0.058 µmol L-1. The sensor can realize the real-time detection of NIC and EVG concentration in cigarette samples quickly and accurately, and has good anti-interference, repeatability and stability.

Electrochemical Removal of Metal-Organic Complexes in Metal Plating Wastewater: A Comparative Study of Cu-EDTA and Ni-EDTA Removal Mechanisms.

Cu and Ni complexes with ethylenediaminetetraacetic acid (Cu/Ni-EDTA), which are commonly present in metal plating industry wastewaters, pose a serious threat to both the environment and human health due to their high toxicity and low biodegradability. In this study, the treatment of solutions containing either or both Cu-EDTA and Ni-EDTA using an electrochemical process is investigated under both oxidizing and reducing electrolysis conditions. Our results indicate that Cu-EDTA is decomplexed as a result of the cathodic reduction of Cu(II) with subsequent electrodeposition of Cu(0) at the cathode when the cathode potential is more negative than the reduction potential of Cu-EDTA to Cu(0). In contrast, the very negative reduction potential of Ni-EDTA to Ni(0) renders the direct reduction of EDTA-complexed Ni(II) at the cathode unimportant. The removal of Ni during the electrolysis process mainly occurs via anodic oxidation of EDTA in Ni-EDTA, with the resulting formation of low-molecular-weight organic acids and the release of Ni2+, which is subsequently deposited as Ni0 on the cathode. A kinetic model incorporating the key reactions occurring in the electrolysis process has been developed, which satisfactorily describes EDTA, Cu, Ni, and TOC removal. Overall, this study improves our understanding of the mechanism of removal of heavy metals from solution during the electrochemical advanced oxidation of metal plating wastewaters.

Electrodeposited copper nanoparticles for creatinine detection via the in situ formation of copper-creatinine complexes.

Creatinine is an important biomarker of kidney diseases. In this work, a fast and facile electrochemical sensor was developed for creatinine detection based on the use of copper nanoparticle-modified screen-printed electrodes. The copper electrodes were prepared by simple electrodeposition of Cu2+ (aq). The electrochemically inactive creatinine was detected reductively via the in situ formation of copper-creatinine complexes. Two linear detection ranges, 0.28-3.0 mM and 3.0-20.0 mM, were achieved using differential pulse voltammetry, with the sensitivities of 0.824 ± 0.053 µA mM-1 and 0.132 ± 0.003 µA mM-1, respectively. The limit of detection was determined to be 0.084 mM. The sensor was validated in synthetic urine samples to yield 99.3% recovery (%RSD = 2.8), demonstrating high tolerance to possible interfering species. Finally, the stability of creatinine and its degradation kinetics at different temperatures were evaluated using our developed sensor. The loss of creatinine was found to be a first-order reaction with the activation energy of 64.7 kJ mol-1.

Electrodeposition of dopamine onto carbon fiber microelectrodes to enhance the detection of Cu2+ via fast-scan cyclic voltammetry.

The etiology of neurodegenerative diseases is poorly understood; however, studies have shown that heavy metals, such as copper, play a critical role in neurotoxicity, thus, adversely affecting the development of these diseases. Because of the limitations associated with classical metal detection tools to obtain accurate speciation information of ultra-low concentrations of heavy metals in the brain, analysis is primarily performed in blood, urine, or postmortem tissues, limiting the translatability of acquired knowledge to living systems. Inadequate and less accurate data obtained with such techniques provide little or no information for developing efficient therapeutics that aid in slowing down the deterioration of brain cells. In this study, we developed a biocompatible, ultra-fast, low-cost, and robust surface-modified electrode with carbon fibers by electrodepositing dopamine via fast-scan cyclic voltammetry (FSCV) to detect Cu2+ in modified tris buffer. We studied the surface morphology of our newly introduced sensors using high-resolution images by atomic force microscopy under different deposition conditions. The limit of detection (LOD) of our surface-modified sensor was 0.01 µM (0.64 ppb), and the sensitivity was 11.28 nA/µM. The LOD and sensitivity are fifty and two times greater, respectively, compared to those of a bare electrode. The sensor's response is not affected by the presence of dopamine in the matrix. It also exhibited excellent stability to multiple subsequent injections and repeated measurements of Cu2+ over a month, thus showing its strength to be developed into an accurate, fast, robust electrochemical tool to monitor ultra-low concentrations of heavy metals in the brain in real time.

Stepwise recycling of Fe, Cu, Zn and Ni from real electroplating sludge via coupled acidic leaching and hydrothermal and extraction routes.

Fe/S-bearing erdite flocculant has been proven to be effective in the precipitation of heavy metals from real electroplating wastewater, with the only drawback being the huge production of sludge. This sludge was rich in Fe/S/Zn/Cu/Ni and refractory to be recycled due to the extractant pollution by free Fe and the dissolution of sulphide. Herein, a multistep separation method was developed to dissolve sulphide and separate Fe prior to Zn/Cu/Ni. Results showed that more than 92% sludge was dissolved as Fe/Zn/Cu/Ni-rich leachate after the sludge was leached by nitric acid, with the rest of the remaining undissolved elemental sulphurs. When the leachate was directly extracted by using commercially extractant Acorga M5640 and Di-(2-ethylhexyl) phosphoric acid (P204), Fe was complexed by the phosphate group of the extractant. The Fe was effectively removed prior to Zn/Cu/Ni to avoid the extractant pollution. The Fe removal efficiency was only 38.34% without sucrose, but it rose to 99.94% with the addition of 0.5 g sucrose. The added sucrose reacted with nitrate to consume H+, which showed a similar rate to the H+ release from Fe hydrolysis. Thereafter, the Fe hydrolysis was continued to remove, the Fe at a high level. The removed Fe was in the form of high-purified hematite nanorod with a diameter and length of 300-600 nm and 0.5-2.5 µm, respectively. After Fe removal, Cu/Zn/Ni was extracted by using Acorga M5640 and P204 to form three halite, including a mixture of copper sulphate hydrate and bonattite (96.8% CuSO4·H2O/CuSO4·3H2O), gunningite (97.5% ZnSO4·H2O) and dwornikite (97.9% NiSO4·H2O). The rest of the solution was neutralised by lime water to remove sulphate as gypsum (95.9% CaSO4) to meet the discharge standard of the electroplating industry. In summary, the recycling efficiency of Fe/Cu/Zn/Ni from the sludge reached 94.4%, 92.6%, 94.7% and 95.3%, which provided an alternative strategy to resource utilise Fe/S-bearing solid waste.

Energy-efficient electrochemical treatment of paracetamol using a PbO2 anode based on pulse electrodeposition strategy: Kinetics, energy consumption and mechanism.

The purpose of this research is to study the pulse electrochemical oxidation of paracetamol (PCT) using a novel PbO2 anode based on pulse electrodeposition strategy (PbO2-PE). The pulse electrodeposition strategy used to prepare a PbO2 anode resulted in rougher surface, higher directional specificity of ß(101) and more redox couples of Pb4+/Pb2+. Additionally, the oxygen evolution potential (OEP) and charge transfer resistance were also improved. When compared to direct current electrochemical oxidation process, pulse electrolysis in had a slightly higher PCT removal efficiency and active species (·OH and active chlorine) production, while 72.04% of energy consumption was saved. The effects of operating parameters on PCT degradation efficiency and specific energy consumption were studied. The findings suggested that the pulse electrochemical oxidation of PCT followed a pseudo-first-order kinetic model, with PCT removal reaching 98.63% after 60 min of electrolysis under optimal conditions. Possible mechanisms describing reaction pathways for PCT were also proposed. Finally, combinating with the economic feasibility and safety evaluation, we could conclude that pulse electrolysis with a PbO2-PE electrode was a promising option for improving the practicability of electrochemical treatment for refractory organic wastewater.

Preparation of copper-based catalysts from electroplating sludge by ultrasound treatment and their antibiotic degradation performance.

The recovery of heavy metals from electroplating sludge is important for alleviating heavy metal pollution and recycling metal resources. However, the selective recovery of metal resources is limited by the complexity of electroplating sludge. Herein, CuFe bimetallic Fenton-like catalysts were successfully prepared from electroplating sludge by a facile room-temperature ultrasonic-assisted co-precipitation method. The prepared CuFe-S mainly consisted of nanorods with diameters of 20-30 nm and lengths of 100-200 nm and a small number of irregular particles. Subsequently, we performed tetracycline (TC) degradation experiments, and the results showed that the product CuFe-S had very good performance over a wide pH range (2-11). At an initial pH = 2, CuFe-S could degrade 91.9% of 50 mg L-1 TC aqueous solution within 30 min, which is better than that of a single metal catalyst. Free radical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that ·OH was the main active species for the degradation of TC by CuFe-S. In conclusion, a CuFe bimetallic Fenton-like catalyst was developed for the catalytic degradation of antibiotics, which provides a novel technical route for the resource utilization of electroplating sludge and shows an important practical application prospect.

Green remediation of Ni, Zn, and Cu in an electroplating contaminated site by wood vinegar with optimization and risk assessment.

Wood vinegar (WV) is a renewable organic compound, possessing characteristics such as high oxygenated compound content and low negative impact on soil. Based on its weak acid properties and complexing ability to potentially toxic elements (PTEs), WV was used to leach Ni, Zn, and Cu contaminated soil in electroplating sites. In addition, the response surface methodology (RSM) based on the Box-Behnken design (BBD) was established to clarify the interaction between each single factor, and finally completed the risk assessment of the soil. The amounts of PTEs leached from the soil climbed with the increase of WV concentration, liquid-solid ratio, and leaching time, while they surged with the decrease of pH. Under optimal leaching circumstances (the concentration of WV= 100 %; washing time= 919 min; pH= 1.00), the removal rates of Ni, Zn, and Cu could reach 91.7 %, 57.8 %, and 65.0 %, respectively, and the WV-extracted PTEs were mainly from the Fe-Mn oxides fraction. After leaching, the Nemerow integrated pollution index (NIPI) decreased from an initial value of 7.08 (indicating severe pollution) to 0.450 (indicating no pollution). The potential ecological risk index (RI) dropped from 274 (medium level) to 39.1 (low level). Additionally, the potential carcinogenic risk (CR) values reduced by 93.9 % for both adults and children. The results revealed that the washing process significantly reduced the pollution level, potential ecological risk, and health risk. Coupled with FTIR and SEM-EDS analysis, the mechanism of WV removal of PTEs could be explained from three aspects: acid activation, H+ ion exchange, and functional group complexation. In summary, WV is an eco-friendly and high-efficiency leaching material for the remediation of PTEs polluted sites, which will maintain soil function and protect human health.

Quantitative measurement of CA 15-3 cancer biomarker using an electrochemical aptasensor based on the electrodeposition of Au thin film on cauliflower-like rGO-MoS2 nanocomposite.

The present research was conducted to design and construct an electrochemical aptasensor for evaluating carbohydrate antigen 15-3 (CA15-3) as a biomarker for breast cancer. The aptasensor has been fabricated by a gold thin film (AuTF) electrodeposited on a cauliflower-like reduced graphene oxide-molybdenum sulfide nanocomposite (rGO-MoS2). The modified electrode's surface was used to immobilize the thiolated aptamer, which was subsequently treated with CA 15-3 antigen. The aptasensor fabrication process was assessed using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). This research also applied EIS to the quantitative measurement of CA 15-3 antigen by the proposed aptasensor. The interfacial charge transfer resistance (Rct) alteration before and after incubation of CA 15-3 by the immobilized aptamer was considered a signal for the quantitative measurement of CA 15-3. A linear concentration ranging from 5.0 to 200.0 U mL-1 with a detection limit of 3.0 × 10-1 U mL-1 was obtained for CA 15-3 using the EIS method. This designed aptasensor indicates satisfactory repeatability and stability, good selectivity, and high sensitivity. Moreover, clinical samples were assayed by the prepared aptasensor and compared with the ELISA method, yielding acceptable results. The recovery and relative standard deviation (RSD) of CA 15-3 in human serum samples were in the range 95.0 to 107.0% and 3.5 to 7.5%, respectively.

A Simple Reversed Iontophoresis-Based Sensor to Enable In Vivo Multiplexed Measurement of Plant Biomarkers Using Screen-Printed Electrodes.

The direct quantification of plant biomarkers in sap is crucial to enhancing crop production. However, current approaches are inaccurate, involving the measurement of non-specific parameters such as colour intensity of leaves, or requiring highly invasive processes for the extraction of sap. In addition, these methods rely on bulky and expensive equipment, and they are time-consuming. The present work reports for the first time a low-cost sensing device that can be used for the simultaneous determination of sap K+ and pH in living plants by means of reverse iontophoresis. A screen-printed electrode was modified by deposition of a K+-selective membrane, achieving a super-Nernstian sensitivity of 70 mV Log[K+]−1 and a limit of detection within the micromolar level. In addition, the cathode material of the reverse iontophoresis device was modified by electrodeposition of RuOx particles. This electrode could be used for the direct extraction of ions from plant leaves and the amperometric determination of pH within the physiological range (pH 3−8), triggered by the selective reaction of RuOx with H+. A portable and low-cost (<£60) microcontroller-based device was additionally designed to enable its use in low-resource settings. The applicability of this system was demonstrated by measuring the changes in concentration of K+ and pH in tomato plants before and after watering with deionised water. These results represent a step forward in the design of affordable and non-invasive devices for the monitoring of key biomarkers in plants, with a plethora of applications in smart farming and precision agriculture among others.

Recovery of Ni matte from Ni-bearing electroplating sludge.

In this study, a novel process for the recovery of Ni from Ni-bearing electroplating sludge (ES) is proposed, which involves the carbothermic reduction stage and smelting stage. In the reduction stage, the CaSO4, Fe2O3, and NiO in the ES were reduced by carbon at 1000 °C, and the Ni3S2 and Fe4Ni5S8(Ni-rich phases) were generated. After that, the reduced ES was mixed with SiO2 and smelted at 1500 °C. During the smelting stage, Ni3S2 and Fe4Ni5S8 were melted to form liquid Ni-Fe-S matte and separated from the molten slag by gravity. Finally, 58.5%Ni-13.8%Fe-27.7%S (in weight) matte and vitrified slag were obtained. The recovery ratio of Ni (97.2%) was much higher than that of Fe (14.7%). Besides, the Ni/Fe mass ratio of the ES was 0.7, while the ratio of the prepared matte was about 4.2. Therefore, the selective recovery of Ni was achieved. The obtained Ni matte can be used as the raw material for pure Ni or Ni-bearing chemicals.

Pyrometallurgy treatment of electroplating sludge, emulsion mud and coal ash: ZnAlFeO4 spinel separation and stabilization in calcium metasilicate glass.

Electroplating sludge was a hazardous waste comprised of heavy metals and other Fe/Al/Ca/Si impurities, and produced massively in surface treatment industry. In the past, it was commonly purified via hydrometallurgy, chlorination and reduction calcination routes, but also blended as additive in rotary kiln, to stabilize the heavy metals in geopolymer. Herein, an alternative strategy was developed to treat a real electroplating sludge for recycling magnetic Zn-rich spinel and stabilizing Zn in calcium metasilicate glass via a facile pyrometallurgy route with the blending of emulsion mud and coal ash. The sludge contained 35.6% Zn and 0.54% Cr and then was blended with 50% emulsion mud. After calcination at 1200 °C, the product was highly dispersed, whilst octahedral ZnAlFeO4 spinel with Zn content of 40.0% were formed and separated by using magnet, in accordance with the recycling efficiency of 51.2% Zn from the electroplating sludge. But after calcination at 1400 °C, the gypsum in emulsion mud was decomposed as CaO and accelerated the dissolution of Si-bearing substance as calcium metasilicate glass for covering ZnAlFeO4 spinel, resulting in the Zn leaching of 1568 mg/L. By adding 50% Si-rich coal ash in the calcination system, more calcium metasilicate glass were generated, and then the Zn concentration in the toxic leaching test was only 12.09 mg/L. During the calcination, Cr showed similar performance to Al/Fe and involved in the spinel formation. This provided a new route to recycle Zn from Zn-rich electroplating sludge and to solidify heavy metals via calcium metasilicate glass route.

Exploration of the Mass Sensitivity of Quartz Crystal Microbalance under Overtone Modes Using Electrodeposition Method.

With the in-depth application of quartz crystal microbalance (QCM) sensors in the fields of science and engineering, there is an urgent need for QCM sensors with high mass sensitivity. The mass sensitivity of a QCM is closely related to its resonance frequency, and the high resonance frequency leads to improve its mass sensitivity. However, the resonance frequency of a QCM resonator cannot be increased all the time due to the fragility of quartz wafer and the limits of energy trapping effect. Few studies are associated with mass sensitivity of a QCM resonator under overtone modes. Herein, we propose to make a QCM resonator work in its n-th overtone (n = 3, 5, 7, 9 in this study) mode to increase its resonance frequency during operating. Thereby, the purpose of improving QCM mass sensitivity is achieved, and the mass sensitivity of a QCM working in the n-th overtone mode can be called as n-th overtone mass sensitivity. Then, the n-th overtone mass sensitivity of a QCM sensor is measured by an electrodeposition method. The experimental results show that the n-th overtone mass sensitivity of a QCM is a bit more than n times that of the fundamental mass sensitivity, and it is consistent with the theoretical calculation results. The application of overtone mass sensitivity will greatly improve the sensitivity of QCM sensors, which is very attractive for the research fields that require QCM sensors with high sensitivity.