Ratio Of Thiourea Research Articles

Nitrogen and sulfur co-doped mesoporous carbon as an efficient peracetic acid activator for the degradation of 4-chlorophenol: A nonradical mechanism dominated by singlet oxygen

Metal-free peracetic acid (PAA) activators are urgently required due to their low toxicity. Heteroatom doping is beneficial to improve the catalytic performance of carbon materials, but the activation performance of doped carbon materials on PAA and the underlying mechanism have not been reported. Herein, nitrogen and sulfur co-doped mesoporous carbons (NS-MC-x, with x representing the mass ratio of thiourea:mesoporous carbon) were fabricated and used as efficient PAA activators for 4-chlorophenol (4-CP) degradation. The NS-MC-1.0/PAA system can remove > 95 % of 4-CP within 10 min, far more than the MC/PAA system. Co-existing anions show no effect on the degradation of 4-CP, whereas humic acid has a certain degree of inhibition. Singlet oxygen (1O2) primarily drives the degradation of 4-CP, with a secondary contribution from a direct electron transfer process mediated by reactive surface complexes, while the contribution of radicals is minimal. In addition, NS-MC-1.0 exhibits excellent reusability for PAA activation, which is conductive to its practical application. This study facilitates further research on metal-free catalysts for PAA activation and offers fresh perspectives on the utilization of PAA in degrading emerging pollutants.

Premise setting for sustainable developing adsorption in environmental remediation using graphitic carbon nitride@agar-derived porous carbon composite

In the adsorption process for wastewater treatment, the adsorbent plays an important role. A composite adsorptive material composed of graphitic carbon nitride and agar-derived porous carbon (CNPC) was fabricated from simple precursors (melamine, thiourea, and agar) and through a facile procedure with different melamine and thiourea ratios. Characterization of CNPC proved a successful formation of a porous structure consisting of mesopores and macropores, wherein CNPC holds distinctive electrochemical (lowered resistance and higher specific capacity) and photochemical properties (lowered bandgap to 2.33 eV) thanks to the combination of graphitic carbon nitride (CN) and agar-derived porous carbon (PC). Inheriting the immanent nature, CNPC was subjected to the adsorption of methylene blue (MB) dye in an aqueous solution. The highest adsorption capacity was 133 mg/g for CNPC-4 which was prepared using a melamine to thiourea ratio of 4:4 – equivalent to the removal rate of 53.2 % and following the pseudo-I-order reaction rate. The effect of pH points out that pH 7 and 9 were susceptible to maximum removal and pretreatment is not required while the optimal ratio of 7.5 mg of MB and 30 mg of material was also determined to yield the highest performance. Furthermore, the reusability of the material for three consecutive cycles was evaluated based on two methods pyrolysis at 200 °C and photocatalytic degradation by irradiation under visible light. In general, the photocatalytic regeneration pathway is more ample and efficient than pyrolysis in terms of energy efficiency (saving energy over 10 times) and adsorption capacity stability. As a whole, the construction of accessible regenerative and stable adsorbent could be a venturing step into the sustainable development spearhead for industries.

Co-adsorption of tetracycline and copper by the thiourea-modified porous sodium alginate microspheres

The gradual increase of antibiotics and heavy metals in aquatic environments poses a serious threat to human health and ecosystems, and finding effective methods for simultaneous removal of antibiotics and heavy metals has attracted increasing concern. In this study, a novel porous structure of thiourea-modified sodium alginate microspheres (UA-Ca) was synthesized by modification with thiourea, epichlorohydrin, and calcium chloride, and was applied for the simultaneous removal of tetracycline (TC) and Cu(II) from water. The results indicated that the UA-Ca material with 1:2 mass ratio of thiourea and sodium alginate showed the highest removal of TC and Cu(II) under the reaction condition of pH= 7. The removal process of both TC and Cu(II) follows the pseudo-second-order adsorption model and Langmuir isotherm model. UA-Ca had a high adsorption capacity toward TC and Cu(II) with the maximum value of 1.099 mmol/g and 2.793 mmol/g based on the Langmuir model at 298 K, respectively. Thermodynamical parameters revealed that TC and Cu(II) adsorption is spontaneous with endothermic nature. Competing ionic cations (Ca2+、Mg2+、NH4+) and organics (sulfamethoxazole, hygromycin) had a certain inhibitory effect on the removal of TC and Cu(II) by UA-Ca, whereas the anionic ions (CO32-、PO43-、SO42-) all had little effect on its removal. Fourier transform infrared spectra and X-ray photoelectron spectroscopy analyses showed that the removal of TC and Cu(II) by UA-Ca was mainly due to electrostatic adsorption and surface complexation. This work provides a promising UA-Ca material for the effective removal of TC and Cu(II) in contaminated water.

Sb2S3 Thin-Film Solar Cells Fabricated from an Antimony Ethyl Xanthate Based Precursor in Air.

The rapidly expanding demand for photovoltaics (PVs) requires stable, quick, and easy to manufacture solar cells based on socioeconomically and ecologically viable earth-abundant resources. Sb2S3 has been a potential candidate for solar PVs and the efficiency of planar Sb2S3 thin-film solar cells has witnessed a reasonable rise from 5.77% in 2014 to 8% in 2022. Herein, the aim is to bring new insight into Sb2S3 solar cell research by investigating how the bulk and surface properties of the Sb2S3 absorber and the current-voltage and deep-level defect characteristics of solar cells based on these films are affected by the ultrasonic spray pyrolysis deposition temperature and the molar ratio of thiourea to SbEX in solution. The properties of the Sb2S3 absorber are characterized by bulk- and surface-sensitive methods. Solar cells are characterized by temperature-dependent current-voltage, external quantum efficiency, and deep-level transient spectroscopy measurements. In this paper, the first thin-film solar cells based on a planar Sb2S3 absorber grown from antimony ethyl xanthate (SbEX) by ultrasonic spray pyrolysis in air are demonstrated. Devices based on the Sb2S3 absorber grown at 200 °C, especially from a solution of thiourea and SbEX in a molar ratio of 4.5, perform the best by virtue of suppressed surface oxidation of Sb2S3, favorable band alignment, Sb-vacancy concentration, a continuous film morphology, and a suitable film thickness of 75 nm, achieving up to 4.1% power conversion efficiency, which is the best efficiency to date for planar Sb2S3 solar cells grown from xanthate-based precursors. Our findings highlight the importance of developing synthesis conditions to achieve the best solar cell device performance for an Sb2S3 absorber layer pertaining to the chosen deposition method, experimental setup, and precursors.

Heteroatoms intra-actions and oxidant-pollutant competition over BC2O sites in N, S, B-tri-doped biochar for the nonradical activation of peroxymonosulfate

Tri-doping effect on the catalytic activity of biochar remains limitedly explored. In this study, N, S, B-tri-doped biochar was fabricated via a one-pot calcination technique. The effects of calcination temperature and boric acid (BA):thiourea (heteroatom precursors) ratio on the surface properties and catalytic performance of the biochar were systemically investigated to elucidate the heteroatoms intra-actions during the doping process. Increasing the calcination temperature from 500 to 800 °C significantly increased the BC2O content, reduced atomic percent (at.%) of S by over 95 %, and had minimal effect on graphitic N content. Increasing the BA:thiourea ratio had a generally positive effect on BC2O content and promoted pyrrolic and pyridinic N formation. Furthermore, BCO2 groups vigorously competed against S over doping sites in the biochar structure. The catalytic performance of the tri-doped biochar as peroxymonosulfate (PMS) activator was studied using tetracycline (TC) as the model pollutant. A more effective catalytic activity can be obtained at higher calcination temperature and BA:thiourea ratio. The catalytic performance was found to withstand different water matrixes and conditions. The chemical scavenger studies and electrochemical analysis stipulated a major contribution of nonradical activation pathway with a competitive behavior between PMS and TC over adsorption and activation on the catalyst surface, with BC2O playing a decisive role in PMS activation. Lastly, based on the identified TC degradation intermediates, the TC degradation pathways were proposed, and the toxicity of these intermediates was evaluated. Overall, the results of this study show that tri-doping can potentially produce an effective PMS activator for practical applications.

Facile synthesis of neuronal nickel–cobalt-manganese sulfide for asymmetric supercapacitors with excellent energy density

A neuronal nickel–cobalt–manganese sulfide material with a large surface area and high porosity can be homogeneously grown along a nickel foam via a simple one-step hydrothermal procedure. An optimal molar ratio of Ni, Co, Mn, and thiourea of 3:1:1:5 was obtained by adjusting the molar ratio of thiourea. This binder-free composite material supported by a nickel foam can be directly used as a battery-type electrode for supercapacitors. Under the optimal hydrothermal conditions, the battery-type electrode exhibited excellent electrochemical properties with a favorable specific capacitance (2805.3F/g, 1 A/g) and good rate properties (87.7 %, 10 A/g) because of the synergistic effect of the multiple transition metals. Furthermore, the battery-type electrode exhibited a remarkable capacitance retention rate (82.9 %, 10 A/g) after 10,000 cycles of electric charging and discharging owing to the addition of Mn, which suggests excellent cycle stability. Furthermore, an asymmetric supercapacitor (ASC) device prepared using the battery-type electrode material and activated carbon electrode exhibited a considerable energy density (86.9 W h kg−1) at a high power density (799.1 W kg−1). After charging for 26 s to 3.2 V, two ASC devices in series could light two red-light-emitting diodes for at least 300 s. Thus, a simple and effective synthesis scheme can be designed to prepare high-performing supercapacitors.

Boosting the energy density of supercapacitors by constructing hybrid molybdenum disulphide nanostructures as a highly durable novel electrode

Hierarchical MoO3@MoS2/rGO nanocomposites with highly active sites deliver high power density and energy density are fabricated here by using a simple two-step process, the first one is a direct anion-exchange reaction of the inorganic MoO3 nanorods (NRs) for growth of few-layered MoS2 nanosheets in a perpendicular direction and other is the composition of rGO sheets with core–shell MoO3@MoS2. Interestingly, how the modification of hybrid solvent in the anion-exchange mechanism and the concentration of thiourea impact on the morphologies of core–shell MoO3@MoS2 at quantum level have been inspected. A fruitful synergistic effect between MoO3/MoS2 core–shell nanostructures and rGO nanosheets led to a high surface area and transporting properties are inspected obviously through fundamental studies. Therefore, in eventual, this novel and more active sites MoO3@MoS2/rGO hierarchical structures material has delivered an outstanding specific capacitance of 525.06F/g at 4 A/g when used as an electrode in supercapacitor and more importantly good stability (80.6% at 10 A/g) even after 1000 successive cycles has been procured in an electrode in which MoS2 shell layer prepared at 5 mmol thiourea ratio.

Nitrogen, sulfur co‐doped porous carbon via high internal phase emulsion template and its potential application as the electrode of high‐performance supercapacitor

AbstractHeteroatom doped carbonaceous material with high specific surface area (SSA) is vital for assembling advanced supercapacitor. Here, a moderate and valid strategy is proposed to synthesize N, S co‐doped porous carbons (NSPCs) which are derived from porous resorcinol‐melamine‐formaldehyde‐thiourea (RMFT) resins via high internal phase emulsion (HIPE) template. The morphology, structure, porous characteristics and chemical ingredients of the prepared NSPCs are investigated by SEM, XRD, Raman spectra, and XPS systematically. The obtained NSPCs show typical open‐cell morphology. As the molar ratio of thiourea to melamine (T/M) increased from 0:1 to 2:1, the SSA of NSPC increases gradually from 927 to 1721 m2 g−1. Electrochemical tests show that when T/M is 2:1, the specific capacity of NSPC reaches 213.5 F g−1 at 1 A g−1. After 10,000 charge–discharge cycles at 10 A g−1, the retention ratio of specific capacitance is 99.6%, indicating an excellent cycling stability. Excellent performances together with facile preparation make NSPC via HIPE template a potential candidate as electrode of advanced supercapacitors.

Reaction between Ce4+ Ion and Thiourea in Aqueous HCl Medium: An Electrochemical Study

Although thiourea is used as a reductant to inhibit Cl2 production in the HCl leaching of rare earth roasted ores containing Ce(IV), no relevant reports provide theoretical support. Herein, an electrochemical test is designed to detect the intermediate and end products that may be generated during the reaction of Ce4+ ion and thiourea in HCl solution, and to reveal the influence laws of key conditions on the reduction peak potential of Ce4+ ion by cyclic voltammetry. The results show that Ce4+ ion is preferentially reduced by thiourea in aqueous HCl medium, which proves thiourea effectively inhibits Cl2 production. Thiourea reacts with Ce4+ ion to produce the intermediate ([(SCN2H4)2]2+) and the final products (SO4 2−, NH3 and CO2) during the irreversible reaction, and the stoichiometric ratio of thiourea to Ce4+ ion is at most 1:8. In addition, the reduction peak potential of Ce4+ ion decreases with the increase of the ratio of F− to Ce4+ (0 ∼ 2 mol mol−1) and temperature (25 ∼ 40 °C), but it is independent of Ce4+ concentration (0.04 ∼ 0.12 mol l−1). This work provides basic theoretical research for industrial application of thiourea and suggests a new route to find a cleaner reductant for avoiding Cl2 generation in the recovery of rare earths.

All‐cellulose composites prepared by partially dissolving cellulose using NaOH/thiourea aqueous solution

AbstractAll‐cellulose composites (ACCs) were prepared by partially dissolving cellulose in the filter paper using NaOH/thiourea aqueous solution. The effects of dissolution time, thiourea ratio, and temperature on the properties of ACCs were investigated. ACCs were characterized by scanning electron microscope, attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray diffraction, and tensile tests. The results revealed that the fibers in ACCs were tightly intertwined. The crystalline form of cellulose in ACCs was transformed from type I to type I/II mixture, and the crystallinity decreased from 77.32 to 51.40%. The tensile strength of ACCs was remarkably improved to 23.16 MPa. The results confirmed ACCs had a high potential for practical applications in the packaging field.

Insight into the influence of doped oxygen on active sites of molybdenum sulfide materials in hydrogen evolution reaction

Molybdenum disulfide has received great attention as a promising non-noble catalyst for electro-catalyzed hydrogen evolution reaction. The active sites originated from the limited edge of crystalline molybdenum disulfide is the key to restrict its HER performance. To increase the active sites of molybdenum disulfide through the heteroatom doping with effective synthetic strategy has become the focus of activity improvement. Herein, a facile and efficient strategy was adopted to synthesize oxygen-doped molybdenum sulfide catalyst by utilizing thiourea and sodium molybdate as precursors. It was found that the number of active sites could be regulated by controlling the dosage ratio of thiourea to sodium molybdate. The doped oxygen and abundant S endows molybdenum sulfide a great deal of lattice disorder or defects, thus providing adequate active sites. When the optimized ratio of thiourea to sodium molybdate (40:1), the double layer value of oxygen-doped molybdenum sulfide reached 34.14 mF/cm2 (mass loading on glassy carbon electrode was 0.142 mg/cm2) which is considered to be proportional to the electrochemical active area. Raman spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of Mo–O bond and bridging S22− bonds which endows molybdenum sulfide with a great deal of lattice disorder or defects, thus providing plentiful active sites.

Understanding of the effect of nitrogen-doping level and micropore volume ratio on the capacitive performance of N,S-codoped hierarchically porous carbon

Four new N,S-codoped hierarchically porous carbons (NSHPCs) with similar sulfur content while obviously different nitrogen content and ratio of micropore volume to total pore volume (Vmicro/Vtot) are synthesized. It is found that the nitrogen content and the Vmicro/Vtot ratio of NSHPCs increase with the increasing of the mass ratio of thiourea to CaCl2. Electrochemical results indicate that reasonable N-doping level is favorable to enhancing the intrinsic capacitance, but excessive high N-doping level leads to many defect sites and then increases the charge transfer resistance; furthermore, the Vmicro/Vtot ratio displays an important effect on determining the rate performance of NSHPCs. Thus the NS-132 sample, obtained from the pyrolysis of the a mixed precursor containing of sugar bagasse, CaCl2 and thiourea in a mass ratio of 1:3:2 at 800 °C for 2 h, possesses nitrogen content of 8.67 atm% and Vmicopore/Vtotal ratio of 46.6% and displays the best capacitive performance. It exhibits high specific capacitances of 357.8, 376.4 and 237.8 F g−1 in 6 M KOH, 1 M H2SO4 and 2 M Li2SO4 at 1.0 A g−1, respectively. A symmetric capacitor prepared from the NS-132-based electrodes displays high energy, good power densities (18.0 Wh⋅kg−1 at 16.9 kW kg−1) and 95.4% capacitance retention capability after 10 000 cycles at 10.0 A g−1 in 2.0 M Li2SO4 electrolyte. These results provide a guidance for the structure design and an easy synthesis route for the NSHPCs with high electrochemical performance.

Preparation of Copper Sulfide by Microwave Assisted Method and Its Application on Superhydrophobic, Anti-UV and Photocatalytic Cotton Fabric

In this work, solid spherical and hollow spherical CuS were prepared by microwave assisted method with PEG4000 as dispersant. The CuS was characterized by particle size analysis, scanning electron microscope(SEM), nitrogen adsorption and desorption, and X-ray diffraction (XRD), respectively. The effects of PEG4000, ratio of thiourea: copper, and microwave power on particle size of CuS were discussed, and the effects of particle size on photocatalytic property were evaluated. The solid spherical CuS had average particle size of 189.1 nm and specific surface of 9.54 m2/g. The hollow spherical CuS had average particle size of 502.7 nm and specific surface area of 16.01 m2/g. The results showed the hollow spherical CuS had better photocatalytic property. In addition, the cotton fabric was treated by hollow spherical CuS/polydimethylsiloxane (PDMS) to prepare multifunctional textile in this work. The treated cotton fabric was characterized by SEM. The treated cotton fabric achieved the superhydrophobicity with contact angle of 156.9° and sliding angle of 8°, good photocatalytic properties for methylene blue, and exceptional UV resistance with UPF of 223.52.

Crystal design, thermal and dielectric behavior of novel silver (Ag) co-ordinated thiourea single crystals

Novel silver co-ordianted thiourea adducts was synthesized by mechanochemical stirring process. Structural data of TuAgN (1:1) and TuAgN (4:1) were collected with the help of single crystal X-ray diffractometer and their unique structural properties were studied and compared. The ratio of the compounds 1:1 and 4:1 represents the mole ratio of thiourea and silver nitrate which has taken for the synthesis. i.e. TuAgN (1:1) indicates, 1 mole of thiourea and 1 mole of silver nitrate and TuAgN (4:1) reveals, 4 mole of thiourea and 1 mole of silver nitrate. The crystalline materials belong to Triclinic and Tetragonal systems with a space group of P-1 and I41 respectively. In both the crystal systems, a single Ag atom co-ordinate with three thiourea ligands and the chain is continued through Ag to Ag interactions. TG/DTA study provides the details of thermal stability and thermal decomposition behavior of the crystals. Electrical characterizations like dielectric constant, dielectric loss and their importance were studied at different temperatures (40, 60 and 80 °C) in the frequency range from 50 Hz to 5 MHz.

Surface-dominated storage of heteroatoms-doping hard carbon for sodium-ion batteries

Though the intercalation mechanism of hard carbon anodes for Na-ion batteries (NIBs) gain decent electrochemical performances, the sluggish diffusion kinetics of Na-ions at low potential present huge challenge to high power applications. To improve the rate capability and cycling stability, especially the performance at high rates, herein, a novel N, S co-doping strategy based on the pseudocapacitive mechanism is developed via one-step synthesis, which endows the hard carbon with excellent rate performances and long-term cycling stability. Moreover, the electrochemical behaviors of N, S co-doping carbon materials outperform those of single heteroatom (N) doping materials, owing to the additional effective covalent S bonds and more defects. The optimized NSC2 (derived from 2:1 mass ratio of thiourea and sodium citric) delivers a high reversible capacity of 280 ​mAh g−1 at 0.05 ​A ​g−1 for 200 cycles and 223 ​mAh g−1 at 1 ​A ​g−1 for 2000 cycles, respectively, and preserves 102 ​mAh g−1 at 10 ​A ​g−1. This work provides a universal co-doping approach on modification of hard carbon materials for high power battery applications.

Optimizing electronic structure and charge transport of sulfur/potassium co‐doped graphitic carbon nitride with efficient photocatalytic hydrogen evolution performance

Recently, graphitic carbon nitride (CN) has been widely investigated for solar energy conversion through water splitting, but its low photocatalytic activity needs to be further improved and optimized. Herein, S/K co‐doped CN photocatalysts have been fabricated by condensation of thiourea and dithiooxamide followed by post‐treatment in molten salt. As evidenced by XRD patterns and UV–vis DRS plots, the engineering crystalline and electronic structure of all as‐prepared samples have been explored through tailoring the mass ratio of thiourea and dithiooxamide as well as ratio of molten salt/the precursor. After optimization, the as‐prepared S/K co‐doped CN photocatalysts with needle‐like nanorods structure exhibit excellent hydrogen evolution rate of 1962.10 μmol−1 g−1 h−1. While its photocatalytic activity is lower than that of pure CN by molten salt treatment (K‐doped CN) (2066.40 μmol−1 g−1 h−1), which results from that the K content of S/K co‐doped CN photocatalyst is lower than that of K‐doped CN. Moreover, compared with K‐doped CN, S/K co‐doped CN photocatalyst possesses higher photocatalytic performance when irradiated by a light source (λ > 520 nm). This might be ascribed to the fact that the introduction of sulfur can expand light absorption region (λ > 520 nm), whereas K cannot improve light absorption of CN in this wavelength region. Furthermore, DFT calculation reveals that both S and K atoms can offer more electrons to band gap, leading to the formation of metallic‐character band structure. In addition, K atom can intercalate in the interlayer of CN and bridge the adjacent two layers, leading to the formation of charge delivery channels. These results demonstrate that S/K co‐doped CN photocatalysts facilitate the separation and transport of photogenerated charge carries, resulting in the efficient photocatalytic activity for hydrogen evolution. Besides, a competition between sulfur and potassium atom during the synthesis process is also discussed in details.

Morphological and electrical characterizations of dip coated porous TiO2 thin films with different concentrations of thiourea additives for resistive switching applications

Dip coating process was used as a synthesis technique for the fabrication of porous TiO2 thin films, where titanium (IV) n-butoxide precursor was used along with Pluronic F-127 and thiourea additives. In this research, thiourea to precursor molar ratio was varied from 0 to 10%, whereas the concentration of the F127 was kept as 3 mM. The post-synthesis structural, morphological, optical and electrical characteristics of the porous TiO2 thin films were investigated. The FESEM micrographs have shown the surface modulation with the different molar ratio of thiourea, whereas the XRD patterns have depicted the evolution of anatase phase of the TiO2 films. The capacitance–voltage measurements were carried out to study the charge densities associated with the TiO2 films. It has been revealed that the films, deposited with 8% molar ratio of thiourea, have possessed higher density of oxide and interface charges. The films, synthesized at 8% thiourea, have also shown better bipolar resistive switching properties as revealed from the current–voltage characteristics of TiO2 memristors.

MnCo2S4 nanoparticles anchored to N- and S-codoped 3D graphene as a prominent electrode for asymmetric supercapacitors

Binary composites MnCo2S4 nanoparticles are potential and attractive materials for supercapacitors. Here, we synthesis the MnCo2S4 nanoparticles anchored on both N and S co-doped 3D graphene composites via a facile two-step controlled sulfurization route. Thiourea contents shows strong effect on the nanostructures and electrochemical properties of the 3D composites. When adjusting the molar ratio of thiourea to Mn2+ as 48:1, the optimal composite electrode achieves a largest specific capacitance of 1324.3 F g−1 at 1 A g−1, with high conductivity, excellent rate performance and outstanding cyclic stability due to its unique structural advantages. Moreover, we fabricate an asymmetric supercapacitor with an operating voltage of 1.5 V using the composite and N, S co-doped graphene nanosheets as both electrodes and it delivers a high energy density of 62.9 Wh kg−1 at a power density of 0.74 kW kg−1, and 28.0 Wh kg−1 at a power density of 1.80 kW kg−1, which are higher than those of reported similar devices. These results prove that the design and optimization of MnCo2S4 and graphene composites is a method to achieve high performance supercapacitors.

Thiourea bioleaching for gold recycling from e-waste

Recycling and reuse of electronic wastes (e-wastes) are becoming an increasingly critical strategy for securing metal resources as well as for minimizing environmental impacts. Thiourea leaching of gold (Au) from e-wastes can be considered an alternative to highly toxic cyanidation, provided that its reagents consumption can be largely reduced. While awareness of the use of biohydrometallurgical techniques in metal mining industries is increasing, the knowledge on microbiological precious metal solubilization is still limited. This led us to investigate and clarify for the first time the potential utility of microbiologically-mediated thiourea leaching (TU-bioleaching) of Au, with a special focus on reducing the reagents consumption while facilitating Au dissolution. Initial screening tests found that different Fe-oxidizing bacteria/archaea possessed varying degrees of thiourea tolerance (5–100 mM). When thiourea and PCB (Printed Circuit Boards) co-exist, Acidiplasma sp. Fv-Ap displayed the most robust Fe-oxidation. The Eh level during the reaction was first optimized by fluctuating the initial ratio of thiourea to Fe3+ (TU:Fe3+ = 2:1–40:1, by using 1 mM Fe3+ vs. 2–40 mM thiourea). The ratio precisely determined the Eh level during the TU-bioleaching and dictated the fate of thiourea decomposition and the resultant Au dissolution from PCB. Microbial contribution to Fe3+ regeneration was seen to support steady and continuous Au dissolution, enabling 98% Au dissolution while using low reagent concentrations of 1 mM Fe3+ and 10 mM thiourea under the microbial Eh control at around 490–545 mV. This novel TU-bioleaching process offers a new alternative approach for Au recycling from e-wastes and minimization of environmental hazards.

A Facile Synthesis of WS2/g‐C3N4 Composites with Improved Photocatalytic Activity

Visible‐light‐driven photocatalysis has received considerable attention in the environmental treatment in recent years. In this paper, WS2/g‐C3N4 composite photocatalysts with various contents of WS2 and g‐C3N4 were synthesized by a facile method via heating the mixtures of tungstic acid and thiourea, and denoted as nWCN, where n is weight ratio of thiourea to tungstic acid. The composites were characterized by XRD, SEM, EDS, TEM, IR, Raman spectroscopy, XPS, TGA, and UV–vis DRS. The characterizations reveal that the composites contain WS2 nanosheets coated by g‐C3N4 and the relative content of WS2 in the composites decreases with increasing amount of thiourea in the reaction mixtures. All the composites exhibited the better photocatalytic activity in degradation of methylene blue in aqueous solution than the single components, WS2, and g‐C3N4. Among them, 7WCN sample performed the highest activity. A synergistic effect between WS2 and g‐C3N4 in photocatalytic activity for the composites was observed.