A novel method to remove chromium, vanadium and ammonium from vanadium industrial wastewater using a byproduct of magnesium-based wet flue gas desulfurization

Deep-sea microorganisms-driven V5+ and Cd2+ removal from vanadium smelting wastewater: Bacterial screening, performance and mechanism

The disorderly discharge of industrial wastewater containing heavy metals has caused serious water pollution and ecological environmental risks, ultimately threatening human life and health. Biological treatment methods have obvious advantages, but the existing microorganisms exhibit issues such as poor resistance, adaptability, colonization ability, and low activity. However, a wide variety of microorganisms in deep-sea hydrothermal vent areas are tolerant to heavy metals, possessing the potential for efficient treatment of heavy metal wastewater. Based on this, the study obtained a group of deep-sea microbial communities dominated by Burkholderia-Caballeronia-Paraburkholderia through shake flask experiments from the sediments of deep-sea hydrothermal vents, which can simultaneously achieve the synchronous removal of vanadium and cadmium heavy metals through bioreduction, biosorption, and biomineralization. Through SEM-EDS, XRD, XPS, and FT-IR analyses, it was found that V(V) was reduced to V(IV) through a reduction process and subsequently precipitated. Glucose oxidation accelerated this process. Cd(II) underwent biomineralization to form precipitates such as cadmium hydroxide and cadmium carbonate. Functional groups on the microbial cell surface, such as -CH2, C=O, N-H, -COOH, phosphate groups, amino groups, and M-O moieties, participated in the bioadsorption processes of V(V) and Cd(II) heavy metals. Under optimal conditions, namely a temperature of 40 °C, pH value of 7.5, inoculation amount of 10%, salinity of 4%, COD concentration of 600 mg/L, V5+ concentration of 300 mg/L, and Cd2+ concentration of 40 mg/L, the OD600 can reach its highest at 72 h, with the removal efficiency of V5+, Cd2+, and COD in simulated vanadium smelting wastewater reaching 86.32%, 59.13%, and 61.63%, respectively. This study provides theoretical insights and practical evidence for understanding the dynamic changes in microbial community structure under heavy metal stress, as well as the resistance mechanisms of microbial treatment of industrial heavy metal wastewater.

Efficient reduction of vanadium (V) with biochar and experimental parameters optimized by response surface methodology

Water pollution deteriorates ecosystems and has a great threaten to the environment. The environmental benefits of wastewater treatment are extremely important to minimize pollutants. Here, the biochar purchased from the related industry was used to treat the wastewater which contained high concentration of vanadium (V). The concentration of vanadium was measured by the IC-OES and the results showed that 96.1% vanadium (V) was reduced at selected reaction conditions: the mass ratio of biochar to vanadium of 5.4, reaction temperature of 90 °C, reaction time at 60 min and concentration of H2SO4 of 10 g/L, respectively. Response surface methodology confirmed that all the experimental parameters had positive effect on the reduction of vanadium (V), which could improve the reduction efficiency of vanadium (V) as increased. The influence of each parameter on the reduction process followed the order: A (Concentration of H2SO4) > C (mass ratio of biochar to vanadium) > B (mass ratio of biochar to vanadium). Especially, the mass ratio of biochar to vanadium and concentration of H2SO4 had the greatest influence on the reduction process. This paper provides a versatile strategy for the treatment of wastewater containing vanadium (V) and shows a bright tomorrow for wastewater treatment.

Study on the performance of vertical flow constructed wetland microcosm with Canna sps. for treatment of high chromium-containing wastewater

Chromium (Cr (VI)) pollution has plagued the environment due to chromite mining and various industrial actions. Constructed wetlands (CW) have emerged as a potential wastewater management technique that utilizes physical, chemical, and biological processes. The present study investigates the use of vertical flow-constructed wetlands (CW) using manure-rich garden soil and sand as substrates in planted CW (CW-P) and unplanted CW (CW-UP) to remove Cr (VI) from simulated wastewater. The experiment was performed in two phases, i.e., Phase I and II, in the same system. In Phase I, initial Cr (VI) concentrations were varied between 5 and 200 mg/l at a fixed hydraulic retention time (HRT) of 48 h, while in Phase II, the effect of HRT (24 h, 48 h, and 96 h) was studied at a fixed Cr (VI) concentration of 200 mg/L in the influent. At 24 h, HRT removal efficiencies were 90.20% for CW-P and 86.41% for CW-UP. However, at 96 h of HRT, the system showed nearly the same removal efficiency. Scanning electron microscopy with energy dispersion X-Ray spectroscopy analysis suggested the conversion of Cr (VI) to Cr (III) in soil precipitate and the translocation of Cr (VI) in plant tissues (Canna sps.). Moreover, microbial diversity profiling indicated that microbial diversity involved in pollutant removal differed in both systems. The phytotoxicity test clearly showed the decrease in toxicity level in the treated effluent, concluding the reusability of treated water. This exploratory study suggested that the CW can potentially remove a higher concentration of hexavalent chromium at longer HRT.

Mechanism of simultaneous lead and chromium removal from contaminated wastewater by a schwertmannite-like mineral

In this study, a schwertmannite-like mineral was synthesized for the removal of lead (Pb) and chromium (Cr) from contaminated wastewater. A shaking flask test was performed (150 r/min, 1 h) with FeSO₄·7H₂O, H₂O₂, Na₂SiO₃, and CaCl₂ added for the mineral synthesis reaction. Results show that optimal performance was achieved with the addition of 1.24 g/L FeSO₄·7H₂O, 0.75 g/L H₂O₂, 1.27 g/L Na₂SiO₃, and 0.44 g/L CaCl₂ at a water temperature of 28 °C, with coexisting ion (Na⁺, K⁺, Mg²⁺) concentrations of 1.50 mmol/L and 0.50 mmol/L EDTA as a complexing agent. Under these optimal conditions, maximum Pb and Cr removal rates of 95.08% and 97.99%, respectively, were achieved within the first 1 min of the mineral synthesis reaction, with the synthesis reaction completed by 6 min. The simultaneous removal of Pb and Cr during the schwertmannite-like material synthesis process occurred via electrostatic adsorption and coprecipitation. When the concentration of the complexing agent was increased from 0.75 to 6.03 mmol/L, the Pb removal rate decreased from 71.88 to 35.45%, and the Cr removal rate decreased from 95.13 to 75.07%, showing that Pb and Cr removal exhibited significant levels of inhibition. In contrast, varying reaction temperatures induced no significant differences. The Pb and Cr dissolution rates from Pb/Cr-containing schwertmannite-like minerals were 8.18% and 2.86% after 40 days, respectively. Therefore, the risk of secondary dissolution of heavy metals is small.

Unraveling diverse survival strategies of microorganisms to vanadium stress in aquatic environments

Worldwide vanadium contamination is posing serious risks to ecosystems. Although abilities of microbial communities to cope with vanadium stress using specific survival strategies have been reported, little is known regarding their relative importance and the underlying detoxification/tolerance mechanisms. Herein, we investigated the potential survival strategies of microbial communities and associated pathways in aquatic environments based on geochemistry and molecular biology. High vanadium content was observed for both water (12.6 ± 1.15 mg/L) and sediment (1.18 × 10³ ± 10.4 mg/kg) in the investigated polluted stream. Co-occurrence network investigation implied that microbial communities showed cooperative interactions to adapt to the vanadium-polluted condition. Vanadium was also characterized as one of the vital factors shaping the community structure via redundancy analysis and structural equation models. Based on the metagenomic technology, three survival strategies including denitrification pathway, electron transfer, and metal resistance in innate microbes under the vanadium stress were revealed, with comprehensively summarized vanadium detoxification/tolerance genes. Remarkable role of electron transfer genes and the prevalent existence of resistance genes during detoxifying vanadium were highlighted. Overall, these findings provide novel insights into survival strategies under the vanadium contamination in aquatic environments, which can be of great significance for the identification, isolation, and application of vanadium reducing bacteria in vanadium bioremediation.

Synthesis of green nano sorbents for simultaneous preconcentration and recovery of heavy metals from water

The wastewater containing Cd, Co, Fe, Cu, Cr, Mn, Ni and Pb ions are as trace metal pollutants. Water pollution caused by increment in industrialization and overpopulation reveals a major threat to human health. Adsorption is recognized as the effective and optimum method to remove water contaminations. The amorphous and porous form of silicon dioxide is silica gel widely used as an adsorbent. It can absorb moisture with traces of the target heavy metal ions. This research elaborates a simplistic, and reliable preconcentration column method highly developed for the determination of Cd²⁺, Fe³⁺, Co²⁺, Cr³⁺, Cu²⁺, Mn²⁺, Pb²⁺ and Ni²⁺ ions in model solutions and real water samples by flame atomic absorption spectrometry (FAAS). The proposed operation depends on the retention of the target ions from buffered model solutions on a silica gel filled up a column modified with vanadium(V) oxide sorbent followed by their desorption. SiO₂/V₂O₅ is an efficient adsorbent due to its low cost, eco-friendly and high availability. The adsorbent morphological and interfacial physicochemical characterization was done using scanning electron microscopy, and Fourier transmission infrared spectroscopy, respectively. The 2.92 value achieved for the point of zero charges supports the experimentation for the heavy metal efficient adsorption. Quantitative recoveries were achieved at pH 10 with 50 mg of SiO₂/V₂O₅ mass and adsorption capacity ranged from 28.96 μmol/g (Pb) to 214.86 μmol/g (Fe) with 1114.79 μmol/g in total. Simultaneous preconcentration effect was determined by the interference cations on the sorbent. The LOD varies from 8.42 to 50.56 μg/L and LOQ is achieved from 20.06 to 72.41 μg/L of 15 blank solutions. The developed preconcentration procedure was adequately implemented for the simultaneous analysis of eight metallic ions content in local river samples. The developed vanadium(V) oxide incorporated with silica gel is practicable as an economical and effective adsorbent to eliminate metallic ions from a liquid solution.

A Clean Method for Vanadium (V) Reduction with Oxalic Acid

Water pollution deteriorates ecosystems and is a great threat to the environment. The environmental benefits of wastewater treatment are extremely important to minimize pollutants. Here, the oxalic acid used as reductant was used to treat the wastewater which contained high concentration of vanadium (V). Nearly 100% of vanadium was efficiently reduced at selected reaction conditions. The optimization results simulated by response surface methodology (RSM) analysis indicated the parameters all had significant effects on the reduction process, and followed the order: dosage of oxalic acid > reaction temperature > reaction time > initial pH of vanadium-containing wastewater. The reduction behavior analysis indicated that the pseudo first-order kinetics model could describe well the reduction process with Ea = 42.14 kJ/mol, and was described by the equation as followed: −LnC=K0·[pH]0.1016·[n(O)/n(V)]2.4569·[T]2.2588·exp(−42.14/T)·t.

Deep understanding of sustainable vanadium recovery from chrome vanadium slag: Promotive action of competitive chromium species for vanadium solvent extraction

The complete separation of vanadium (V) and chromium (Cr) from chrome vanadium slag is still challenging. Many studies focus on the activity of vanadium, while the effect of the other element chromium and their mutual interaction are ignored. Here, we found that proper concentration of chromium can promote the extraction efficiency of vanadium. The extraction of V and Cr with various mass ratios ranging from 8:1-4:3 at different initial pH values using primary amine N1923 were studied. The extraction efficiency of V reached nearly 100%, while none of Cr was extracted when the mass ratio of Cr and V is 0.5 under proper pH. Through the dynamic monitoring of species evolutions during extraction, the transformation of the two metals and advantage extracted species were analyzed. Cr would transfer H⁺ for the combination of V₃O₉^3-/V₄O₁₂^4-, providing a great contribution to the continuous extraction of V. The real leachate was applied and 99.9% vanadium pentoxide was produced at a scale of 50 L/h. This paper offers deep insights of the separation of similar metal elements, and guide sustainable vanadium recovery from hazardous waste.

Vanadium in soil-plant system: Source, fate, toxicity, and bioremediation

Vanadium(V) is an important component of industrial activities, while it may pose toxic hazards to plants, animals, and humans at high levels. Owing to its various uses in numerous industrial processes, high amount of V is released into the soil environment. Previous literature has focused on the biogeochemistry and ecotoxicity of V in soil-plant system. Consequently, this overview presents its source, fate, phyto-uptake, phyto-toxicity, detoxification, and bioremediation based on available data, especially published from 2015 to 2020. Vanadium occurs as various chemical forms (primarily as V(V) and V(IV)) in the soil environment, and its biogeochemical behaviour is easily influenced by soil conditions including redox potential, soil pH, organic matter, and microorganisms. Vanadium mainly accumulates in plant roots with very limited translocation to shoots. However, plants such as dog's tail grass and green bean are reported to accumulate high levels of V in aboveground tissues. An insight into the processes and mechanisms that allow plants to absorb and translocate V in soil-plant system is also stressed in this overview. In plants, low levels of V have beneficial effects on plant growth and development. Nevertheless, excessive V provokes numerous deleterious effects including reducing seed germination, inhibiting root and shoot growth, depressing photosynthesis, interfering with nutrients uptake, inducing overgeneration of ROS, and leading to lipid peroxidation. Mechanisms related to detoxification strategies like sequestration in root system, compartmentation in vacuoles and cell wall, and antioxidant defence systems to endure V-induced toxicity in plants are discussed as well. The detailed knowledge of bioremediation involved in the cleanup of V-contaminated soils would immensely help understand and improve the remediation process. Furthermore, this overview outlines several research gaps requiring further investigation in order to advance our understanding of the biogeochemical roles of V in soil-plant systems.

Removal of V(V) From Solution Using a Silica-Supported Primary Amine Resin: Batch Studies, Experimental Analysis, and Mathematical Modeling

Every year, a large quantity of vanadium-containing wastewater is discharged from industrial factories, resulting in severe environmental problems. In particular, V(V) is recognized as a potentially hazardous contaminant due to its high mobility and toxicity, and it has received considerable attention. In this study, a silica-supported primary amine resin (SiPAR) was prepared by in-situ polymerization, and the V(V) adsorption from the solution was examined. The as-prepared resin exhibited fast adsorption kinetics, and it could attain an equilibrium within 90 min for the V(V) solution concentration of 100 mg/L at an optimum pH of 4, whereas the commercial D302 resin required a treatment time of more than 3 h under the same conditions. Furthermore, the maximum adsorption capacity of the resin under optimum conditions for V(V) was calculated to be 70.57 mg/g. In addition, the kinetics and isotherm data were satisfactorily elucidated with the pseudo-second-order kinetics and Redlich–Peterson models, respectively. The silica-based resin exhibited an excellent selectivity for V(V), and the removal efficiency exceeded 97% in the presence of competitive anions at 100 mmol/L concentrations. The film mass-transfer coefficient (k_f) and V(V) pore diffusivity (D_p) onto the resins were estimated by mathematical modeling. In summary, this study provided a potential adsorbent for the efficient removal of V(V) from wastewater.

Highly selective adsorption of vanadium (V) by nano-hydrous zirconium oxide-modified anion exchange resin

Adsorption is widely used in removal of toxic vanadium (V) [V(V)] from water streams, and a fit-for-purpose adsorbent plays a vital role in this process. Herein HZrO@D201, an adsorbent with decoration of nanosized hydrous zirconium oxide (HZrO) on anion exchange resin D201, is fabricated for efficient V(V) removal. Compared to pristine D201, HZrO@D201 excelled in V(V) removal with a maximum adsorption capacity of 118.1 mg/g, due to potential formation of inner sphere complexation between V(V) and HZrO. HZrO@D201 could also functioned well in a wide pH range (3.00 to 9.00) and exhibited outstanding selective V(V) adsorption under the presence of competing anions (chloride, nitrate, sulfate, and phosphate). The adsorption thermodynamics was in accordance with the Langmuir model, while adsorption kinetics followed the Pseudo-Second-Order model. When treating actual vanadium contaminated groundwater from Panzhihua region (China), HZrO@D201 indicated a satisfactory lifespan in the column experiment for V(V) removal (2.41 times longer than D201), and the treated groundwater could meet the vanadium standard of drinking water source in China (less than 50 μg/L). Regeneration of HZrO@D201 was easily achievable with negligible capacity loss. Results from this work suggests a promising application potential of HZrO@D201 in vanadium pollution control.

An efficient utilization of high chromium vanadium slag: Extraction of vanadium based on manganese carbonate roasting and detoxification processing of chromium-containing tailings

A novelty roasting method with manganese carbonate (MnCO₃) as additive was carried out to separate and recover vanadium from high chromium vanadium slag (HCVS) efficiently. Vanadium tailings containing chromium was detoxified by carbon reduction and smelting to form Fe-Cr alloy. The whole process of HCVS utilization was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 89.37% of vanadium and 0.10% of chromium was leached when MnCO₃ was added to HCVS at the mole ratio of MnO in MnCO₃ and V₂O₃ in HCVS (n(MnO)/n(V₂O₃)) of 2.0 and heating at 850 °C for 120 min, then leached under the pH value at 2.5. 99.19% of vanadium was precipitated by (NH₄)₂SO₄ and V₂O₅ with a purity of 99.28% was prepared. More than 84% of manganese addictive was recovered after manganese precipitation by carbonization with CO₂ discharged from manganese carbonate roasting, which could be used as the raw addictive for roasting. The wastewater after vanadium and manganese extraction could be circulated as leaching medium. Three circulation routes realized the closed-circuit circulation of raw materials and products, saving the production costs and avoiding the environmental pollution. Fe-Cr alloy with 67.35% of Fe and 13.28% of Cr was obtained from chromium-containing vanadium tailings, which could be returned to the steelmaking process.

An efficient utilization of chromium-containing vanadium tailings: Extraction of chromium by soda roasting-water leaching and preparation of chromium oxide

Chromium-containing vanadium tailings (CCVT), an industrial waste, were utilized to extract chromium efficiently by soda roasting-water leaching process and for the preparation of highly pure chromium oxide. The effect of extraction of chromium under different roasting and leaching conditions were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The maximum chromium extraction rate of 91.51% was obtained when soda (Na₂CO₃) and CCVT were mixed in a molar ratio (n (Na₂CO₃)/n (Cr₂O₃)) of 8, roasted at 900 °C and maintained for 120 min. Then, the roasted product was leached in water at 60 °C for 60 min with a liquid-solid mass ratio (L/S) of 10. During soda roasting, the chromium-containing phase (Fe_0.6Cr_0.4)₂O₃ combines with Na₂CO₃ to form Na₂CrO₄, which was then transferred into the leaching liquid, post water leaching. The by-products such as NaFeTiO₄, Na₂CaSiO₄, and Na_0.68Fe_0.68Si_0.32O₂ were left in the leaching residue which was called chromium tailings (CT). 87.40% chromium oxide was recovered from the unpurified leaching liquid after reduction and precipitation by adding Na₂S, followed by roasting the deposit. This process not only relieved the potential threat of the industrial waste CCVT to the environment but also realized the recovery of the valuable element chromium.

Rhizosphere Microbial Response to Multiple Metal(loid)s in Different Contaminated Arable Soils Indicates Crop-Specific Metal-Microbe Interactions

In this study, we sampled rhizosphere soils from seven different agricultural fields adjacent to mining areas and cultivated with different crops (corn, rice, or soybean), to study the interactions among the innate microbiota, soil chemical properties, plants, and metal contamination. The rhizosphere bacterial communities were characterized by Illumina sequencing of the 16S rRNA genes, and their interactions with the local environments, including biotic and abiotic factors, were analyzed. Overall, these soils were heavily contaminated with multiple metal(loid)s, including V, Cr, Cu, Sb, Pb, Cd, and As. The interactions between environmental parameters and microbial communities were identified using multivariate regression tree analysis, canonical correspondence analysis, and network analysis. Notably, metal-microbe interactions were observed to be crop specific. The rhizosphere communities were strongly correlated with V and Cr levels, although these sites were contaminated from Sb and Zn/Pb mining, suggesting that these two less-addressed metals may play important roles in shaping the rhizosphere microbiota. Members of Gaiellaceae cooccurred with other bacterial taxa (biotic interactions) and several metal(loid)s, suggesting potential metal(loid) resistance or cycling involving this less-well-known taxon.IMPORTANCE The rhizosphere is the "hub" for plant-microbe interactions and an active region for exchange of nutrients and energy between soil and plants. In arable soils contaminated by mining activities, the rhizosphere may be an important barrier resisting metal uptake. Therefore, the responses of the rhizosphere microbiota to metal contamination involve important biogeochemical processes, which can affect metal bioavailability and thus impact food safety. However, understanding these processes remains a challenge. The current study illustrates that metal-microbe interactions may be crop specific and some less-addressed metals, such as V and Cr, may play important roles in shaping bacterial communities. The current study provides new insights into metal-microbe interactions and contributes to future implementation and monitoring efforts in contaminated arable soils.

A novel resource utilization method using wet magnesia flue gas desulfurization residue for simultaneous removal of ammonium nitrogen and heavy metal pollutants from vanadium containing industrial wastewater

In the present study, a novel resource utilization method using wet magnesia flue gas desulfurization (FGD) residue for the simultaneous removal of ammonium nitrogen (NH₄–N) and heavy metal pollutants from vanadium (V) industrial wastewater was proven to be viable and effective. In this process, the wet magnesia FGD residue could not only act as a reductant of hexavalent chromium [Cr(vi)] and pentavalent vanadium [V(v)], but also offered plenty of low cost magnesium ions to remove NH₄–N using struvite crystallization. The optimum experimental conditions for Cr(vi) and V(v) reduction are as follows: the reduction pH = 2.5, the wet magnesia FGD residue dose is 42.5 g L⁻¹, t = 15.0 min. The optimum experimental conditions for NH₄–N and heavy metal pollutants removal are as follows: the precipitate pH = 9.5, the n(Mg²⁺) : n(NH₄⁺) : n(PO₄³⁻) = 0.3 : 1.0 : 1.0, t = 20.0 min. Finally the NH₄–N, V and Cr were separated from the vanadium containing industrial wastewater by forming the difficult to obtain, soluble coprecipitate containing struvite and heavy metal hydroxides. The residual pollutant concentrations in the wastewater were as follows: Cr(vi) was 0.047 mg L⁻¹, total Cr was 0.1 mg L⁻¹, V was 0.14 mg L⁻¹, NH₄–N was 176.2 mg L⁻¹ (removal efficiency was about 94.5%) and phosphorus was 14.7 mg L⁻¹.

A novel resource utilization method using wet magnesia flue gas desulfurization residue for the simultaneous removal of ammonium nitrogen and heavy metal pollutants from vanadium industrial wastewater was proven to be viable and effective.

Enhancement of synchronous bio-reductions of vanadium (V) and chromium (VI) by mixed anaerobic culture

The co-occurrence of toxic vanadium (V) and chromium (VI) in groundwater receives incremental attention while knowledge on their interactions in biogeochemical processes is limited, with lack of efficient removal means. This study is the first to realize synchronous bio-reductions of V(V) and Cr(VI) with high efficiency by mixed anaerobic culture. After 72-h operation, 97.0 ± 1.0% of V(V) and 99.1 ± 0.7% of Cr(VI) were removed, respectively, with initial concentration of 1 mM for both V(V) and Cr(VI). Cr(VI) bio-reduction took priority while V(V) detoxification was inhibited. V(IV) and Cr(III) were the identified reduction products, both of which could precipitate naturally. Initial Cr(VI) and acetate concentrations as well as pH affected this process significantly. High-throughput 16S rRNA gene sequencing analysis indicated the accumulation of Anaerolineaceae, Spirochaeta and Spirochaetaceae, which could contribute to V(V) and Cr(VI) bio-reductions. The new knowledge obtained in this study will facilitate understanding the biogeochemical fate of co-existing V(V) and Cr(VI) in groundwater and development of bioremediation strategy for their induced combined pollution.

A novel resource utilization of the calcium-based semi-dry flue gas desulfurization ash: As a reductant to remove chromium and vanadium from vanadium industrial wastewater

A novel resource utilization of the calcium-based semi-dry flue gas desulfurization ash is investigated. In the present study, the semi-dry desulfurization ash is used as a reductant for chromium and vanadium removal by chemical reduction precipitation, the byproduct gypsum and chromium-contained sludge are obtained. Besides, the effects of main operational parameters (reaction pH, desulfurization ash dosage and reaction time) on the heavy metal removal are investigated, and the main reaction mechanism for this treatment technology is also proposed. Under the optimal conditions, the residual concentrations of Cr(VI), total Cr and V are 0.163mg/L, 0.395mg/L and 0.155mg/L, respectively. Additionally, byproduct gypsum and chromium-contained sludge are characterized using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and thermogravimetry differential scanning calorimetry (TG-DSC), respectively. Finally, the resource utilization methods of the byproduct gypsum and chromium-contained sludge from this technology are also submitted. The byproduct gypsum can be utilized to produce hemihydrate calcium sulfate whisker, and the roasted heavy metal precipitation can be used as a primary chromium raw material (Cr₂O₃ content is about 83%).