Formation Of CdS Research Articles

Cadmium recovery from acid leachates of Tunisian phosphoric acid purification residues.

The management of cadmium-rich sludges, which are pollutant residues from the phosphorus industry, including the valorization of these sludges through the selective recovery of heavy metals, is a promising prospect. However, there is still a need to develop recovery methods that are both optimized for efficiency, cost-effectiveness, and environmentally friendly. This study aims to enhance cadmium extraction from the polymetallic sludge by optimizing the processes of sulfuric acid (SA) leaching and sodiumsulfide precipitation. Key parameters including SA concentration, temperature, solid/liquid ratio, and stirring velocity were optimized to maximize the heavy metals extraction. Over 90% of the Cd and Zn present in the sludge were successfully extracted. Subsequently, investigates the selective precipitation of metal sulfide from acidic leachates (pH < 2), focusing particularly on cadmium. Through the optimization of chemical precipitation parameters (Na2S concentration, temperature, and reaction time), more than 99% of the cadmium was selectively recovered as CdS. The precipitates underwent analysis for mineralogy, chemistry, purity, and particle size. XRD analyses indicated CdS formation in "Greenockite" and "Hawleyite" forms, confirmed by SEM-EDS data, revealing fine powder consisting of micro and nanoparticles (< 0.5 µm) with varied spherical shapes.

ZnS and CdS nano thin films – A comprehensive analysis of structural, morphology and optical properties for photovoltaic applications

The current study is on the deposition of Zinc Sulfide and Cadmium Sulfide thin films by chemical bath deposition (CBD) technique. The deposited films were annealed at 200 °C and 350 °C in vacuum system. The Structural, Surface morphology, elemental composition and Optic analysis were performed by XRD, SEM, EDX, PL and optical transmission spectra. The XRD confirmed the formation of ZnS and CdS which revealed a broad spectrum in the low 2θ region due to its amorphous behaviour. The average optical transmission spectrum of ZnS lies between 65 % and 80 % and CdS lies between 50 and 60 %. The optical band gap of both the annealed films was decreasing with increase in temperature. The higher optical transmittance observed from emission spectra of PL analysis can contribute better performance and proved that the annealed ZnS and CdS thin films are applicable for photovoltaic applications.

Regulatory roles of APS reductase in Citrobacter sp. XT1-2-2 as a response mechanism to cadmium immobilization in rice

Citrobacter sp. XT1-2-2, a functional microorganism with potential utilization, has the ability to immobilize soil cadmium. In this study, the regulatory gene cysH, as a rate-limiting enzyme in the sulfur metabolic pathway, was selected for functional analysis affecting cadmium immobilization in soil. To verify the effect of APS reductase on CdS formation, the ΔAPS and ΔAPS-com strains were constructed by conjugation transfer. Through TEM analysis, it was found that the adsorption of Cd2+ was affected by the absence of APS reductase in XT1-2-2 strain. The difference analysis of biofilm formation indicated that APS reductase was necessary for cell aggregation and biofilm formation. The p-XRD, XPS and FT-IR analysis revealed that APS reductase played an important role in the cadmium immobilization process of XT1-2-2 strain and promoting the formation of CdS. According to the pot experiments, the cadmium concentration of roots, culms, leaves and grains inoculated with ΔAPS strain was significantly higher than that of wild-type and ΔAPS-com strains, and the cadmium removal ability of ΔAPS strain was significantly lower than that of wild-type strain. The study provided insights into the exploration of new bacterial assisted technique for the remediation and safe production of rice in cadmium-contaminated paddy soils.

The correlation of the drain-source capacitance variation and the P-pillar structures in a 4H-SiC quasi super junction MOSFET

In order to improve the trade-off between the 4H-SiC planar Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and super junction MOSFET (SJ-MOSFET), particularly on the drain to source capacitance (Cds) which affects the switching performance, this study investigates the Cds of the quasi SJ-MOSFETs with various P-pillar widths, depths, and concentrations. The measured results show (1) when the N-type region between the P-pillars (Epi-1 region) is fully depleted, the Cds value abruptly drops, (2) when the N-type drift region beneath the P-pillar (Epi-2 region) is fully depleted, the slope of the Cds-Vds curve slowly changes because of the small extension of the depletion region in the P-type region. This is because the wider P-pillar width will increase the magnitude of the abrupt drop of the Cds and make the drop occur earlier; the abrupt drop of the Cds will occur later and the magnitude increases when the P-pillar depth is deeper due to the larger P-type region; Moreover, increasing the P-pillar concentration not only initiates the abrupt drop earlier and increases the magnitude, but also increases the minimum saturation value of the Cds at a higher reverse bias. This study also reveals that the mechanism of the Cds formation in a quasi SJ-MOSFET is different from the planar MOSFET and SJ-MOSFET. Finally, the simulated results are used to validate the influence of the P-pillar structures on the Cds – Vds curves in a quasi SJ-MOSFET.

Real-time monitoring of CdTe quantum dots growth in aqueous solution

Quantum dots (QDs) are remarkable semiconductor nanoparticles, whose optical properties are strongly size-dependent. Therefore, the real-time monitoring of crystal growth pathway during synthesis gives an excellent opportunity to a smart design of the QDs luminescence. In this work, we present a new approach for monitoring the formation of QDs in aqueous solution up to 90 °C, through in situ luminescence analysis, using CdTe as a model system. This technique allows a detailed examination of the evolution of their light emission. In contrast to in situ absorbance analysis, the in situ luminescence measurements in reflection geometry are particularly advantageous once they are not hindered by the concentration increase of the colloidal suspension. The synthesized particles were additionally characterized using X-ray diffraction analysis, transition electron microscopy, UV-Vis absorption and infrared spectroscopy. The infrared spectra showed that 3-mercaptopropionic acid (MPA)-based thiols are covalently bound on the surface of QDs and microscopy revealed the formation of CdS. Setting a total of 3 h of reaction time, for instance, the QDs synthesized at 70, 80 and 90 °C exhibit emission maxima centered at 550, 600 and 655 nm. The in situ monitoring approach opens doors for a more precise achievement of the desired emission wavelength of QDs.

Synthesis, structural and optical characterization of CdxZn1−xS/FNBRnanocomposites

AbstractCdxZn1−xS nanoparticles have been synthesized on the base of functionalized nitrile butadiene rubber (FNBR) by SILAR method and characterized by various techniques. Both binary and ternary sulfide nanocrystals have been obtained in the cubic phase with very high purity at room temperature. The average particle size decreased from 2.49 nm to 2.22 nm and then increased to 2.44 nm by the increasing of zinc concentration from 25 % to 50 % and 75 %. The calculated Young's modulus for (111), (220) and (311) planes are 97.84, 78.51 and 64.33 m2 N−1 for CdS and 95.84, 69.68, 53.42 m2 N−1 for ZnS, respectively. The band corresponding PO32− (977 cm−1) shifted to 969, 975, 972, 973, and 972 cm−1 upon the formation of CdS, ZnS, Cd0.5Zn0.5S, Cd0.75Zn0.25S and Cd0.25Zn0.75S nanoparticles into FNBR matrix, which is explained by Hooke's Law. EPR spectra of CdS/FNBR nanocomposite show broad and singlet asymmetric, isotropic symmetry (gx=gy=gz). The appearance of a new line in the 3518 G magnetic field is observed in both CdS and Cd0.5Zn0.5S compounds’ spectra.The total mass loss of the samples NBR, FNBR, Cd2+ and Zn2+ ions containing FNBR are 93.76, 59.77, 60.03 and 57.79 %, respectively. High crystallinity is caused by complete interaction of metal ions with functional groups during the nucleation.

Cysteine and thiosulfate promoted cadmium immobilization in strain G303 by the formation of extracellular CdS

Bacteria have evolved a variety of strategies to defend themselves against cadmium toxicity, however, the specific mechanisms involved in the enhancement of bacterial cadmium resistance by sulfur sources are unclear. In this study, a novel cadmium (Cd)-tolerant bacterium, Stenotrophomonas geniculata G303, was isolated from activated sludge. The growth of strain G303 under diverse Cd concentrations was investigated, and the minimum inhibitory concentration of Cd was found to be 1 mM. Strain G303 effectively remove 94.7 % of Cd after 96 h of culture. Extracellular CdS was detected using multiple methods, with the CdS formed being aggregated in the biofilm. The addition of cysteine and thiosulfate to the medium significantly enhanced the Cd resistance and removal capacity of strain G303. Integrated genomic and proteomic analyses revealed that heavy metal transporters cooperate to resist Cd stress. Cysteine and thiosulfate improved Cd tolerance in strain G303 by upregulating nitrogen and energy metabolism. Proteins associated with nitrate reduction likely played a pivotal role in cysteine and thiosulfate metabolism. Notably, cysteine synthase and the SUF system played crucial roles in CdS formation. This study systematically explored the impact of cysteine and thiosulfate on the Cd resistance of strain G303, deepening our understanding of the microbial response mechanism to heavy metals.

One-Step Photochemical Preparation of CdS/Poly(MMA-co-MAA) Composite with Enhanced Photocatalytic Activity.

This paper presents a one-step photochemical method for the preparation of CdS/Poly(MMA-co-MAA) composite photocatalyst, based on the concept of simultaneous photocatalytic polymerization of organic monomers during UV-light induced formation of CdS. The preparation is carried out in an aqueous solution of Na2S2O3, CdSO4, methyl methacrylate (MMA) and methacrylic acid (MAA), under a UV lamp. The continuously formed CdS particles with photocatalytic activity act the role of initiator to directly initiate the copolymerization of MMA and MAA, resulting in the in situ formation of the composite and full contact of the CdS particles with the oxygen-containing groups in the polymer. Taking the photocatalytic degradation of methylene blue as a case study, the composite exhibited significantly higher activity under simulated solar light compared to the pure CdS. By analysis on various data, the enhanced photocatalytic activity is attributed to the enhanced visible light absorption, and especially the high electron-hole separation efficiency caused by the electrostatic interaction between photogenerated holes and carbonyl oxygen atoms with negatively charged features. Furthermore, the composite displays excellent sunlight activity and recyclability, suggesting its potential for practical applications. Such a one-step construction strategy relying only on photo-energy is green, low-cost and promising in obtaining high-performance semiconductor/polymer composite photocatalysts.

Impact of iron and sulfur cycling on the bioavailability of cadmium and arsenic in co-contaminated paddy soil

The biogeochemical cycling of iron (Fe) or sulfur (S) in paddy soil influences the cadmium (Cd) and arsenic (As) migration. However, the influence of coupled reduction effects and reaction precedence of Fe and S on the bioavailability of Cd and As is still not fully understood. This study aimed to reveal the influence of Fe and S reduction on soil Cd and As mobility under various pe + pH conditions and to elucidate the related mechanism in subtropical China. According to the findings, higher adsorption from Fe reduction caused high-crystalline goethite (pe + pH > 2.80) to become amorphous ferrihydrite, which in turn caused water-soluble Cd (62.0%) to first decrease. Cd was further decreased by 72.7% as a result of the transformation of SO42- to HS-/S2- via sulfate reduction and the formation of CdS and FeS. As release (an increase of 8.1 times) was consequently caused by the initial reduction and dissolution of iron oxide (pe + pH > 2.80). FeS had a lesser impact on the immobilization of As than sulfate-mediated As (V) reduction in the latter stages of the reduction process (pe + pH < 2.80). pe + pH values between 3 and 3.5 should be maintained to minimize the bioavailability of As and Cd in moderate to mildly polluted soil without adding iron oxides and sulfate amendments. The practical remediation of severely co-contaminated paddy soil can be effectively achieved by using Fe and S additions at different pe + pH conditions. This technique shows promise in reducing the bioavailability of Cd and As.

PVA/CdS-Ag Nanocomposites: Effect of Composition and UV Radiation on Optical, Electrical and Structural Properties

PVA incorporated with different content of CdS-Ag nanostructures are prepared using chemical reduction technique. Along with this these nanocomposites are exposed to UV radiated for different times. The X-ray spectraof PVA /CdS-Ag nanocomposites indicatethe formation of CdS and Ag nanostructures within PVA.Changes in the band structure of nanocomposites with and without UV exposure are studied by UV-Visible spectroscopy. Absorbance and refractive index are noticed to show increment with the concentration of nanostructures and time of exposure. Along with this, the behaviour of different optical parameters such as E0 and Ed is investigated. FE-SEM and EDX analysis exhibit microstructural modification occurring in nanocomposites due to changes in the concentration of incorporated nanostructures and UV radiation. Influence of concentration and UV exposure on conductivity and dielectric parameters on PVA/CdS-Ag nanocomposites are studied.

Bacteria-loaded biochar for the immobilization of cadmium in an alkaline-polluted soil.

The combination of biochar and bacteria is a promising strategy for the remediation of Cd-polluted soils. However, the synergistic mechanisms of biochar and bacteria for Cd immobilization remain unclear. In this study, the experiments were conducted to evaluate the effects of the combination of biochar and Pseudomonas sp. AN-B15, on Cd immobilization, soil enzyme activity, and soil microbiome. The results showed that biochar could directly reduce the motility of Cd through adsorption and formation of CdCO3 precipitates, thereby protecting bacteria from Cd toxicity in the solution. In addition, bacterial growth further induces the formation of CdCO3 and CdS and enhances Cd adsorption by bacterial cells, resulting in a higher Cd removal rate. Thus, bacterial inoculation significantly enhances Cd removal in the presence of biochar in the solution. Moreover, soil incubation experiments showed that bacteria-loaded biochar significantly reduced soil exchangeable Cd in comparison with other treatments by impacting soil microbiome. In particular, bacteria-loaded biochar increased the relative abundance of Bacillus, Lysobacter, and Pontibacter, causing an increase in pH, urease, and arylsulfatase, thereby passivating soil exchangeable Cd and improving soil environmental quality in the natural alkaline Cd-contaminated soil. Overall, this study provides a systematic understanding of the synergistic mechanisms of biochar and bacteria for Cd immobilization in soil and new insights into the selection of functional strain for the efficient remediation of the contaminated environments by bacterial biochar composite.

Room Temperature Exsolution of Cds Nanodots on A‐site Deficient Cotton‐Ball Like Titanate Perovskite Nanoparticles for H2 Production Under Visible Light

AbstractExsolution of nanoparticles followed by chemical treatment (“chemistry at a point”) is a very exciting approach to the smart design of functional materials such as visible light active photocatalysts. Unfortunately, the usually utilized thermal reduction approach is not feasible for low melting point metals and compounds such as Cd and CdO. Here a hydrothermal approach to prepare exsolved CdS nanodots on cotton ball‐like perovskite supports is described. The titanate‐based photocatalyst is synthesized using a hydrothermal process followed by room‐temperature sulfidation. The hydrothermal route directs A‐site doping of Cd2+ via hydroxyl group incorporation in the titanate lattice. Formation of CdS via exsolution provides a high H2 production mass activity of 3050 µmol g−1 h−1 under visible light with only 5 mol.% Cd doping of the titanate. Moreover, the strong CdS‐support interaction offers good cycling stability under UV–vis and visible light irradiation. This is the first report describing the exsolution of CdS nanodots at room temperature and shows its advantages for photocatalytic activity.

Simultaneous removal of cadmium(II) and arsenic(III) from aqueous solutions using pyrite-modified biochar: Effects and mechanisms

Simultaneous removal of cadmium [Cd(II)] and arsenic [As(III)] from aqueous systems is still a great challenge. Through mechanical ball milling and thermal activation, pyrite-modified biochar (PMB) was successfully prepared and used to evaluate its synchronous removal effect and mechanism of Cd(II) and As(III) from aqueous solutions. PMB exhibited a maximum adsorption capacity of 51.0 mg·g−1 for Cd(II) (pH=6) and 65.9 mg·g−1 for As(III) (pH=4) at 25 °C, surpassing that of biochar by 1.5 and 5.7 times, respectively. Interestingly, in the mixed Cd-As system, the presence of Cd(II) hindered the adsorption of As(III) onto PMB, while the presence of As(III) enhanced the adsorption of Cd(II). Additionally, the removal of Cd(II) and As(III) by PMB remained in the range of 70%− 80% under the competition of cations (K+, Mg2+) and anions (NO3-, SO42-), except for the severe inhibition of Cd(II) and As(III) removal by Ca2+ and PO43- due to their specific physicochemical properties. The adsorption of Cd(II) by PMB followed the Langmuir and pseudo-second-order models, involving ion exchange (formation of CdS) and complexation as the main removal mechanisms. And the adsorption of As(III) followed the Freundlich and pseudo-second-order models, involving oxidation of As(III) to arsenic(V) and further complexation as the primary removal mechanisms. After four adsorption-desorption cycles, the adsorption performance of PMB for Cd(II) and As(III) could still reach 78% and 68% of the initial performance. Overall, the results demonstrated that PMB was the preferred eco-friendly material for efficiently removing Cd(II) and As(III) from co-pollution aqueous solutions.

Preparation and Characterization of Mercapto-Functionalized Calcined Attapulgite and Its Removal of Pb (II) and Cd (II) Solution

To enhance the sorption efficacy of attapulgite for heavy metals, mercapto-functionalized attapulgite (ATP-SH) was synthesized with mercaptan functional groups. When the mass-to-volume ratio of calcined attapulgite (ATP-C) to 3-Mercapropyltrimethoxysilane (MPTMS) was 1 g:0.5 mL (ATP-SH-0.5) and the pH was set to 8, a strong adsorption capacity for Cd (II) and Pb (II) was demonstrated. This indicates excellent adsorption performance for these heavy metals. ATP-SH-0.5 exhibited a maximum adsorption capacity of 43.81 mg/g and 274.83 mg/g for Cd (II) and Pb (II), respectively, in a single ion system. In a binary ion system, the maximum adsorption capacity was 31.86 mg/L and 254.45 mg/L for Cd (II) and Pb (II), respectively. Various characterizations and experiments showed that the adsorption of Cd (II) and Pb (II) onto ATP-SH-0.5 involves ion exchange reactions involving hydroxyl and thiol functional group complexation reactions. This adsorption process follows a single-molecule layer adsorption mechanism. XPS results indicate that hydroxyl and grafted thiol functional groups on the surface of mercapto-functionalized attapulgite participated in surface complexation reactions with Cd (II) and Pb (II), resulting in the formation of Cd-S and Pb-S species. Overall, this study provides a promising mercapto-functionalized modification material for the remediation of polluted water and soil.

Detailed insights into the formation pathway of CdS and ZnS in solution: a multi-modal in situ characterisation approach.

The high stability, high availability, and wide size-dependent bandgap energy of sulphidic semiconductor nanoparticles (NPs) render them promising for applications in optoelectronic devices and solar cells. However, the tunability of their optical properties depends on the strict control of their crystal structure and crystallisation process. Herein, we studied the structural evolution during the formation of CdS and ZnS in solution by combining in situ luminescence spectroscopy, synchrotron-based X-ray diffraction (XRD) and pair distribution function (PDF) analyses for the first time. The influence of precursor type, concentration, temperature and heating program on the product formation and on the bandgap or trap emission were investigated in detail. In summary, for CdS, single-source precursor (SSP) polyol strategies using the dichlorobis(thiourea)cadmium(II) complex and double-source precursor approaches combining Cd(CH3COO)2·2H2O and thiourea led to the straightforward product at 100 °C, while the catena((m2-acetato-O,O')-(acetate-O,O')-(m2-thiourea)-cadmium) complex was formed at 25 and 80 °C. For ZnS, the reaction between Zn(CH3COO)2·2H2O and thiourea at 100 °C led to the product formation after the crystallisation and dissolution of an unknown intermediate. At 180 °C, besides an unknown phase, the acetato-bis(thiourea)-zinc(II) complex was also detected as a reaction intermediate. The formation of such reaction intermediates, which generally remain undetected applying only ex situ characterisation approaches, reinforce the importance of in situ analysis for promoting the advance on the production of tailored semiconductor materials.

Towards effective dye degradation and antimicrobial behavior of chitosan and C3N4-doped CdS nanoparticles

In this study, co-precipitation has been employed to develop carbon nitride (C 3 N 4 ) and chitosan (CS)-doped CdS nanoparticles (NPs) to investigate the doping effect of CS and C 3 N 4 on CdS to degrade MB dye and assess their antibacterial activity. Comparatively, the maximum dye degradation achieved by the previously reported binary blend of CdS-C 3 N 4 was 85%, whereas the maximum degradation achieved by the currently prepared ternary nano-catalyst was 99.75%. Furthermore, CdS NPs were doped with a fixed amount of CS at various concentrations (2 and 4 wt. %) of C 3 N 4 . Numerous techniques have been utilized to characterize doped NPs. The hexagonal phase of CdS was confirmed by XRD results, and doping caused a decrease in crystallite size, as calculated by the Debye Scherrer formula. Functional group existence was determined by FTIR; CdS was confirmed at 662 and 758 cm −1 , and doped CdS exhibited bond stretching and absorption at 1061, 1388, 1627, and 3434 cm -1 . The UV-Vis absorption spectra with blueshift after doping resulted in increased bandgap energy, which could be attributed to a reduction in crystallite size. PL spectra were utilized to observe the charge carrier transfer and trap sites of doped NPs. The presence of CdS formation and doping was observed using EDS. The morphology of the product was examined using HRTEM, which revealed spherical NPs agglomeration. C 3 N 4 -doped NPs demonstrated significant methylene blue (MB) dye degradation, while doped CdS samples exhibited considerable antimicrobial activity against Staphylococcus aureus and Escherichia coli bacteria.

Mechanism of Chemical Bath Deposition of CdS Thin Films: Influence of Sulphur Precursor Concentration on Microstructural and Optoelectronic Characterizations

In this study, we aimed to improve our understanding of the response mechanisms associated with the formation of CdS thin films. CdS thin film remains the most valuable option for many researchers, since it has shown to be an effective buffer material for film-based polycrystalline solar cells (CdTe, CIGSe, CZTS). We performed experimental and numerical simulations to investigate the effect of different thiourea concentrations on the characteristics of the CdS buffer layer. The experimental results reveal that an increase in thiourea concentrations had a direct effect on the optical results, with bandgap values ranging from (2.32 to 2.43) eV. XRD analysis confirmed that all deposited films were polycrystalline, except for [1/0.75], where there is no CdS formation. Electrical studies indicated that CdS with a molar ratio of [Cd]/[S] of 1 had the maximum carrier concentration (3.21 × 1014 cm−3) and lowest resistivity (1843.9 Ω·cm). Based on the proposed mechanism, three kinds of mechanisms are involved in the formation of CdS layers. Among them, the ion-by-ion mechanism has a significant effect on the formation of CdS films. Besides, modelling studies reveal that the optic-electrical properties of the buffer layer play a crucial role in influencing the performance of a CIGS solar cell.

Evolutionary mechanism of Ni-ZIF/CdS calcination for efficient photocatalytic hydrogen evolution

In this work, we develop Ni/Ni3S2/CdS composite photocatalytic system from annealing of CdS nanosphere coated Ni-ZIF by simple solvothermal method. The Ni/Ni3S2/CdS synthesized after calcination at 700 °C exhibits the best hydrogen evolution performance with an average hydrogen evolution rate of 2104.02 μmol/g/h, which is 152 times higher than that of pure CdS, and external quantum efficiency is 41.9% (λ = 420 nm). Using a series of characterization methods, we revealed that CdS is the photosensitizer, Ni is the catalytic active species, and Ni3S2 formed between Ni and CdS formation plays an important role in charge separation as confirmed by time resolved emission spectroscopy. In addition, the regulation of Ni loading is achieved by changing the annealing time and the molar ratio of Ni salt to CdS. These results demonstrate that Ni/Ni3S2/CdS is a favorable photocatalyst for efficient photocatalytic hydrogen evolution.

Influence of γ-radiation on the physical characteristics of thermally evaporated nanostructured CdS: Cl films

Thermally evaporated CdS: Cl films were subjected to gamma irradiation with an equivalent dose intensity of 4.11 kG/hour for extended periods (60 to 240) minutes. The resultant films were examined by different approaches to acquire structural, morphological and optical information. Upon gamma irradiation doses, the samples show variation in grain size, dislocation density, microstrain and texture coefficient. The XRD patterns exhibit the hexagonal crystal structure formation of CdS: Cl. FESEM images disclosed an extensive spherical nature of nanocrystallites. They demonstrated an increase in their size, while optical study reveals a decrease in bandgap (Eg) and an increase in Urbach energy (EU) due to gamma doses. Electrical studies display a reduction in resistivity upon irradiation doses of gamma. These tailored films can find application as window layers in optoelectronic devices.

Up-flow anaerobic column reactor for sulfate-rich cadmium-bearing wastewater purification: system performance, removal mechanism and microbial community structure.

This study constructed an up-flow anaerobic column reactor fed with synthetic sulfate-rich cadmium (Cd(II))-bearing wastewater, for investigating its Cd(II) removal performance and mechanism. Long-term experiment results manifest that introducing Cd(II) into influent led to an enhanced sulfate removal but did not increase the effluent sulfide concentration, implying the CdS formation. When influent Cd(II) concentration was shifted from 50 to 100mg/L, the median Cd(II) removal rate was increased from 13.6 to 32.2mg/(L·d). Batch tests indicate that the uptake and sequestration function of anaerobes merely led to a small portion of Cd(II) removal. A majority of aqueous Cd(II) (86.3%) was eliminated by precipitation reactions. The generated precipitates were found to be dominantly presented in carbonate, Fe-Mn oxide, sulfide bound and residue forms, which account for 92.6-93.9% of total Cd content of sludge obtained at diverse operation phases. The crystallographic CdS (i.e., residue fraction) particles have nano-scale sizes, and the relatively high atomic ratio of S to Cd was likely due to the adsorption/deposition of other sulfides. The dominant sulfate-reducing bacteria (SRB) were recognized as Desulfurella, Desulforhabdus and Desulfovibrio, and the primary competitor with them for substrate utilization were identified to be methanogens.