Processing Residues Research Articles

Remediation of Cr(VI)-contaminated soil mixed with chromite ore processing residue by ferrous sulfate and enzyme residue

In this study, Cr(VI)-contaminated soil mixed with COPR by using ferrous sulfate (FeSO4), enzyme residue (ER), and their combination under aerobic or anaerobic condition were investigated. The concentration of Cr(VI) decreased from 1498.05 to 104.63 mg kg−1 after the simultaneous addition of FeSO4 (30 %, w/w as FeSO4·7H2O) and ER (30 %, w/w) at 45 d under the anaerobic condition with a reduction efficiency of 93.02 %, which is higher than that by single FeSO4 (72.39 %) or ER (75.47 %) under the anaerobic condition. XRD, XPS, FTIR, and fluorescence spectroscopy were conducted to characterize soil and ER composition. Metagenomic analysis was performed to reveal the reduction mechanisms of FeSO4 and ER. The anaerobic condition with lower Eh was beneficial for Cr(VI) reduction than aerobic condition, and Eh was the main driver for the evolution of Cr(VI) reduction-related microorganisms. Moreover, the addition of ER enriched the organic matter and microbials in the soil. During the decomposition of organic matter under the anaerobic condition, organic acids were generated, leading to a decrease in pH and promoting the release of Cr(VI) from minerals. They also served as electron donors in Cr(VI) reduction. Additionally, the addition of excess FeSO4 stimulated the growth of iron-reducing bacteria and sulfate-reducing bacteria, facilitating to Cr(VI) reduction. Metagenomic analysis showed that Acinetobacter, related to the nemA and nfsA genes, was the dominant Cr(VI) reduction genus. Thus, the combination of FeSO4 and ER is a promising method for the remediation of Cr(VI)-contaminated soils mixed with COPR.

A Critical Assessment of Extraction Methodologies for the Valorization of Agricultural Wastes: Polyphenolic Profile and Bioactivity

Different extraction techniques were used to exploit fruit processing residues for their use as a source of phenolic compounds. Three different extraction methods, namely microwave-assisted extraction (MAE), subcritical water extraction (SWE), and maceration (M), were assessed to gauge their respective efficacies. Total phenolic content (TPC) and total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), and radical scavenging activity ABTS assay were evaluated. High-performance liquid chromatography was used to assess the polyphenolic profile. MAE was the extraction technique that allowed the highest recovery of polyphenolic compounds. Concerning the fruit by-products analyzed, the extract of pomegranate peels obtained using M60C and MAE had the highest TPC (313 ± 24 mg GAE/g dry weight (dw)) and TFC (36.0 ± 2.8 mg EE/g dw), respectively, and the highest antioxidant activity (FRAP = 740 ± 67 mg AAE/g dw and ABTS (628 ± 27 mg TE/g dw) corresponded to M60C. The phenolic composition obtained for this sample using high-performance liquid chromatographic–diode array detection (HPLC–DAD) showed that gallic acid, protocatechuic acid, β-resorcylic acid, (+)-cathechin, and rutin were the main phenolics found. The findings underscore the capacity of agricultural by-products to act as a source of phenolic compounds. This offers a feasible solution to enhance the nutritional content in food while simultaneously minimizing environmental waste.

Treatment of soybean processing residues for energy recovery and environmental compliance: Technical and economic feasibility

Soybean molasses, a by-product of soy protein concentrate processing, presents environmental disposal issues and therefore researchers and industries have been studying its application. This study investigated methane production from soybean molasses anaerobic digestion at mesophilic conditions in an Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR). The evaluation was focused on the impact of feeding strategy (batch or fed-batch mode), fill time, applied organic loading rate (OLRA), temperature, and co-processing with okara on system stability and performance. The best performance indicators were obtained at an OLRA of 14.9 kg-COD/m3/d, fed-batch mode with 180 min of feed at 30 °C (86% COD removal, 140.9 mol-CH4/m3/d, 11.0 mol-CH4/kg-COD, and 74% of methane in biogas). Crucial anaerobic digestion functional groups, such as hydrolytic and acetogens, were identified. Firmicutes and Proteobacteria were the most abundant phyla. In the inoculum, Euryarchaeota phylum exceeded Proteobacteria. Nine reactors of 3271 m³ each producing 72 GWh/year of energy would be needed to treat 216 tons-molasses/day according to the scale-up estimation using industrial data. A USD 61 M initial investment would be necessary. The net present value, internal rate of return and payback would be of USD 39 M, 14.0% and 13.8 years, respectively.

Organic Molecules as Origin of Visible-Range Single Photon Emission from Hexagonal Boron Nitride and Mica.

The discovery of room-temperature single-photon emitters (SPEs) hosted by two-dimensional hexagonal boron nitride (2D hBN) has sparked intense research interest. Although emitters in the vicinity of 2 eV have been studied extensively, their microscopic identity has remained elusive. The discussion of this class of SPEs has centered on point defects in the hBN crystal lattice, but none of the candidate defect structures have been able to capture the great heterogeneity in emitter properties that is observed experimentally. Employing a widely used sample preparation protocol but disentangling several confounding factors, we demonstrate conclusively that heterogeneous single-photon emission at ∼2 eV associated with hBN originates from organic molecules, presumably aromatic fluorophores. The appearance of those SPEs depends critically on the presence of organic processing residues during sample preparation, and emitters formed during heat treatment are not located within the hBN crystal as previously thought, but at the hBN/substrate interface. We further demonstrate that the same class of SPEs can be observed in a different 2D insulator, fluorophlogopite mica.

Synthesis of betanin by expression of the core betalain biosynthetic pathway in carrot

Betalain has received increased attention because of its high nutritional value and crucial physiological functions. Based on the elucidation of its core biosynthetic pathway, betalain can be produced in additional plants by metabolic engineering. Synthesis of betalain in carrot (Daucus carota L.) can improve its nutritional quality and economic value by extracting betalain from the fleshy root, non-edible part, and processing residue of carrot. In this study, two different constructs, namely, pYB:mCD (AomelOS, BvCYP76AD1S, and BvDODA1S) and pYB:CDD (BvCYP76AD1S, BvDODA1S, and MjcDOPA5GTS), were introduced into carrot for betanin synthesis by Agrobacterium-mediated transformation. Betanin can be synthetized in both transgenic calli, and pYB:mCD-transgenic callus can be used to produce betacyanin by suspension culture. However, pYB:mCD-transgenic seedlings can synthetize betanin only by tyrosine feeding. The pYB:CDD-transgenic lines can synthetize betanin in whole plants. The betanin content in fleshy root of pYB:CDD-transgenic carrot was (63.4 ± 9) μg ·g−1 fresh weight according to quantitative analysis. These betanin-producing carrot plant materials can be used to synthesize betanin for industrial application or consumption as dietary sources.

Thermal degradation kinetics of high‐performance urea‐formaldehyde resin prepared by replacing partial urea with soybean processing residue

AbstractIn this work, soybean meal was applied to replace partial urea to prepare high‐performance urea‐formaldehyde resin (SMUF). The optimum addition amount of soybean meal was screened by the basic properties of resin, the bonding strength and formaldehyde emission of the board. The activation energy (Ea) and reaction kinetics at different conversion rates were estimated by Kissinger and Flynn–Wall–Ozawa methods. The results showed that when 5 wt% soybean meal was used to replace urea, the formaldehyde emission of plywood decreased by 19.23% and the bonding strength increased by 36.29%, which were 0.84 mg L−1 and 1.69 MPa, respectively. Meanwhile, the thermal stability of Urea‐formaldehyde (UF) resin is improved. The thermal degradation Ea of SMUF is higher than that of UF, the reaction kinetic equation of both UF and SMUF are G(α) = [−ln (1 − α)]2. It is feasible to replace partial urea with soybean meal. When the addition level of soybean meal is 5 wt%, SMUF has better comprehensive performance. When the addition level of soybean meal is 10–20 wt%, the bonding strength of plywood is higher than that of UF, but the formaldehyde emission is higher. How to reduce the formaldehyde emission will be the direction of future research.

High-intensity ultrasound-based process strategies for obtaining edible sunflower (Helianthus annuus L.) flour with low-phenolic and high-protein content

The sunflower Helianthus annuus L. represents the 4th largest oilseed cultivated area worldwide. Its balanced amino acid content and low content of antinutrient factors give sunflower protein a good nutritional value. However, it is underexploited as a supplement to human nutrition due to the high content of phenolic compounds that reduce the sensory quality of the product. Thus, this study aimed at obtaining a high protein and low phenolic compound sunflower flour for use in the food industry by designing separation processes with high intensity ultrasound technology. First, sunflower meal, a residue of cold-press oil extraction processing, was defatted using supercritical CO2 technology. Subsequently, sunflower meal was subjected to different conditions for ultrasound-assisted extraction of phenolic compounds. The effects of solvent composition (water: ethanol) and pH (4 to 12) were investigated using different acoustic energies and continuous and pulsed process approaches. The employed process strategies reduced the oil content of sunflower meal by up to 90% and reduced 83% of the phenolic content. Furthermore, the protein content of sunflower flour was increased up to approximately 72% with respect to sunflower meal. The acoustic cavitation-based processes using the optimized solvent composition were efficient in breaking down the cellular structure of the plant matrix and facilitated the separation of proteins and phenolic compounds, while preserving the functional groups of the product. Therefore, a new ingredient with high protein content and potential application for human food was obtained from the residue of sunflower oil processing using green technologies.

BIOFUELS – A NOVEL DIMENSION FOR A SUSTAINABLE FUTURE

The demand for energy has increased globally and the availability of fossil fuel is limited. Added to this, there has been a negative effect on climate due to the emission of greenhouse gases from the burning of fossil fuels. These are the alarming signals to explore unconventional and sustainable energy sources. Biomass energy is becoming popular these days as it is clean and sustainable form of energy. It can potentially solve the problems of waste management and energy security. Growth in industrialization and agricultural sector has witnessed the accumulation of huge biowastes like forest residues, food waste, agriculture crop residues, wood processing residues industrial waste and municipal solid waste (MSW). Biomass from these biowastes have also simultaneously emerged prospective feedstocks for bioenergy production. Production and consumption of biofuel is becoming popular as it will be a novel approach for a sustainable future.

Camu-Camu Flour Processed in Conventional Oven and Solar Dryer: Quality Product and Accessible Low Technology Products as an Opportunity to Family Agriculture

The culture of camu-camu fruit is one of the most promising in the Amazon region; with proper industrialization the fruit could contribute to local food security, which raises excellent opportunities to further elaborate products with higher aggregate value to introduce to population living in natural producing areas. The aim of this research was to carry out a comparison of the agro-industrial and nutritional quality of fruit flour prototypes and residues from the processing of camu-camu dehydrated in a conventional electric oven and an alternative solar dryer, verifying the possibility of obtaining a standardized flour product with the techniques used. The camu-camu fruits was harvested in March of 2018 at Morena Lake, Boa Vista municipality, Roraima State, Brazil and, processed into flour at Embrapa Laboratories. Furthermore, an analysis of moisture, soluble solids, titratable acidity, pH, color and N, P, K, Ca, Mg, S, Cu, Zn, Mn, Fe and B contents of the flour, were carried out and evaluated. The experimental design was completely randomized in a factorial scheme, evaluating three raw materials by two drying methods. The data was statistically validated using an analysis of variance, when there was statistical difference, the means of agroindustrial and elemental characteristics were compared by the T (0.05) and Tukey (0.05) tests. The main quality differences in the interaction between raw materials and drying methods are in moisture, soluble solids, titratable acidity, color and P, K and Ca contents. In general, the macro and microelement contents of the camu-camu flour dehydrated in a hot air oven with forced ventilation, and in a low-cost convection solar dehydrator presented the following order N > K > P > Ca > S > Mg > Mn > Fe > B > Zn > Cu. The evaluated camu-camu flours are presented as alternatives for the integral use of the fruit and processing residues, having satisfactory qualities, with the possibility of being used in agro-industrial products.

Biobutanol Production from Agro-industrial by-products using ABE Fermentation: Analysis of Feedstock Effect on Biobutanol Yield and Titer

This study examined a range of agro-industrial by-products that could be used as potential carbon and nitrogen sources for ABE fermentation. In general, the study examined more than a dozen different by-products from dairy, biodiesel, sugar, agriculture, beverage, food, etc. production industries. The by-products were tested to determine which of them would result in higher biobutanol yield and concentration in the fermentation medium. All by-products were used in the cultivation of three bacteria of the genus Clostridium to observe differences also between the strains’ ability to utilize the respective substrates. The test results demonstrated that the most suitable by-products for ABE fermentation, which served as carbon sources, are biodiesel and sugar production by-products and hydrolysates of agricultural residues. These by-products are available in large quantities. The tests show that they serve as a good energy source for the production of butanol fuel. By-products of dairy processing and specific beverage production residues (yeast residues) showed the best results as the most suitable nitrogen sources; however, these by-products are either limited in availability at scale or their transportation is uncompetitive due to the high water content. This study shows that ABE fermentation can be provided with a range of different agroindustrial by-products. The wider use of these by-products in the future can reduce the negative impact on the environment, reduce the production costs of ABE fermentation products and allow obtaining an efficient biofuel – biobutanol, which can compete with bioethanol and biodiesel.

Immobilization of chromium ore processing residue by alkali-activated composite binders and leaching characteristics.

Chromium ore processing residue (COPR) is classified as hazardous solid waste because of the leachable Cr(VI). Cementitious materials are often used to solidify and stabilize heavy metals. However, most of them focus on the leaching concentration of particles after solidification and stabilization and lack research on leaching characteristics. This study investigated the leaching characteristics of heavy metals in three simulated environments (HJ557-2010, HJ/T299-2007, TCLP) after immobilizing COPR with composite binders. Industrial solid waste coal fly ash and lead-zinc smelting slag are used to prepare composite binders through alkali activation technology. Compressive strength, particle leaching toxicity, acid neutralization capability, and semi-dynamic leaching test are used to evaluate the performance of the solidified body. The solidified body can be applied to building materials or treated as general industrial waste. Heavy metals are mainly released from the matrix by surface washing at a low rate. The analysis results, including XRD, FTIR, and SEM-EDS, show that chemical binding and physical encapsulation are the main immobilizing mechanisms to realize the coordinated disposal of Zn and Cr(VI).

Optimizing Biobutanol Production: Analysis of Feedstock Selection, Pre-treatment Methods, and Microorganism Strains for Biobutanol Production from Agricultural and Industrial By-products

This study presents an analysis of key elements of biobutanol production, including feedstock selection, pre-treatment methods, and microorganism strains. Using laboratory experiments, we evaluated the ability of different microorganisms to convert various agricultural and industrial by-products into biobutanol. We tested three microorganism strains: C. acetobutylicum DSM 792, C. beijerinckii DSM 6423, and C. saccharoperbutylacetonicum DSM 14923. The results showed that biodiesel production residues, various agricultural hydrolysates, yeast residues, and milk processing residues were the most suitable feedstocks for biobutanol production. In addition, the authors explored different pre-treatment methods, such as microbial and chemical hydrolysis, to enhance the efficiency of biobutanol production. Our findings provide valuable insights for optimizing biobutanol production processes in line with sustainable and cost-effective production principles.

Application of a biochar produced from malt bagasse as a residue of brewery industry in fixed-bed column adsorption of paracetamol

We report the removal of paracetamol from aqueous systems using a fixed-bed packed with biochar obtained from pyrolysis of malt bagasse residue (MBR). MBR biochar was characterized by carbonization yield, pH, Fourier-transform infrared spectroscopy (FTIR), and specific surface area (BET method). High surface area biochar (308.6 m² g-1) was fixed in a bed sorption column and sorption capacity was studied by varying the mass of sorbent and sorbate flow rate. Sorption isotherms (breakthrough curves) in the traditional "S" shape were observed in the assays. The nonlinear models of Thomas, Bohart-Adams and Yan-Viraraghavan were applied to the experimental data, with the model of Yan-Viraraghavan best describing the behavior of the isotherms, with a good mean coefficient of determination (R²) of 0.9883. Breakthrough times were greater at lower flow rates and greater sorbent amounts, and the effect of sorbent mass alone upon adsorption capacity (qexp) was not significant for a given flow rate. Thus, beer processing residue can be a source of raw material for the production of value-added MBR biochar, since it showed good sorption results of paracetamol in the biochar fixed-bed column, reaching sorption capacities at equilibrium up to 27.65 mg g-1 depending on the experimental parameters adopted.

Efficient reduction of Cr(VI) and recovery of Fe from chromite ore processing residue by waste biomass

The traditional chromite ore processing residue (COPR) detoxification process is carried out in strong acid or anoxic high-temperature condition, which not only has a high input cost but leading difficulties for resource utilization of treated COPR. This study first reported the efficient reduction of Cr(VI) and recovery of Fe from COPR by waste molasses-assisted hydrothermal treatment. Under optimal conditions (i.e., the Na2CO3 dosing of 0.5 mol/L, the molasses/COPR mass ratio of 10%, hydrothermal treatment at 140 °C for 150 min), the Cr(VI) reduction efficiency reached 99.96 ± 0.01%, and the leaching toxicity of total Cr met the USEPA regulatory limit of 5 mg/L. Moreover, Fe was recycled in the form of magnetic magnesioferrite with Fe2O3 grade of 52.58 ± 0.90%, which can be used as raw material in steel industry. The Cr(VI) reduction reaction conforms to a pseudo-first-order kinetic model, and the reaction rate constants increase with increasing temperature (120 ∼160 °C). As a potential mechanism of the reaction, the Mg-Al hydrotalcite (LDHs) structure collapses in the presence of Na2CO3 during the hydrothermal treatment, and the embedded Cr(VI) is released, which is then reduced to Cr(OH)3 by reducing substances such as fructose, sucrose, and glucose in waste molasses. From the standpoint of a circular economy, this study may provide a potential strategy for minimizing resource input and waste/emission production by harmless disposal and resource utilization of COPR and waste molasses.

Decay resistance of Pterocarpus erinaceus Poir. and the antifungal properties of its extract

The processing residue of Pterocarpus erinaceus was used to obtain an ethanol-extract, whose anti-fungal properties and mode of action was investigated using multi-omics principles and gas chromatography-mass spectrometry. The results showed that the decay resistance of the heartwood of Pterocarpus erinaceus was in Grade I; it showed strong decay resistance. The effective concentration of 70% ethanol extract of the heartwood of Pterocarpus erinaceus was 13.8%. It showed high inhibition against Coriolus versicolor and Gloeophyllum trabeum, and the content of the extract was positively correlated with the diameter of the inhibition zone. Transcriptomics analysis showed there were 93 genes differentially expressed in Gloeophyllum trabeum. Among them, 42 genes were up-regulated and 51 genes were down-regulated. These genes were mainly related to oxidoreductase activity, integral components of the membrane, carbohydrate metabolism, lipid metabolism, and other related Gloeophyllum trabeum life activities. In total, 31 substances were separated and observed using GC-MS, and their peak areas accounted for 91.8% of the total peak area. Of these, 16 substances including ketones, esters, amines, alkanes, olefins and aromatic compounds showed a relatively high content. Ketones accounted for the most abundance at 29.1%. These compounds may represent the main active components of antifungal and decay resistance.

Superabsorbent bacterial cellulose film produced from industrial residue of cashew apple juice processing

The industrial residue of cashew apple juice processing (MRC) was evaluated as an alternative medium for bacterial cellulose (BC) production by Komagataeibacter xylinus ATCC 53582 and Komagataeibacter xylinus ARS B42. The synthetic Hestrin-Schramm medium (MHS) was used as a control for growing and BC production. First, BC production was assessed after 4, 6, 8, 10, and 12 days under static culture. After 12 days of cultivation, K. xylinus ATCC 53582 produced the highest BC titer in MHS (3.1 g·L−1) and MRC (3 g·L−1), while significant productivity was attained at 6 days of fermentation. To understand the effect of culture medium and fermentation time on the properties of the obtained films, BC produced at 4, 6, or 8 days were submitted to infrared spectroscopy with Fourier transform, thermogravimetry, mechanical tests, water absorption capacity, scanning electron microscopy, degree of polymerization and X-ray diffraction. The properties of BC synthesized in MRC were identical to those of BC from MHS, according to structural, physical, and thermal studies. MRC, on the other hand, allows the production of BC with a high water absorption capacity when compared to MHS. Despite the lower titer (0.88 g·L−1) achieved in MRC, the BC from K. xylinus ARS B42 presented a high thermal resistance and a remarkable absorption capacity (14664 %), suggesting that it might be used as a superabsorbent biomaterial.

Applications of Brewer’s Spent Grain Hemicelluloses in Biorefineries: Extraction and Value-Added Product Obtention

A circular economy is imperative for environmental sustainability. In this context, biorefineries stand out as a means of production able to reduce the carbon footprint and the impact of global warming. Biorefineries may employ lignocellulosic biomass from various plant sources to produce bioproducts with the potential to replace fossil derivatives through synthesis by microorganisms without competing with food crops. Brewer’s spent grain (BSG), the residue of the brewery production process, is an option with potential for use, being a cheap raw material highly available throughout the year. The chemical composition of this biomass is quite variable, with significant amounts of hemicellulose, mainly consisting of xylose and arabinose monomers that can be technologically converted into value-added products such as xylooligosaccharides, xylitol, second-generation ethanol (2G ethanol), biofilms and furfural. To this end, catalysts are unusual in making biorefineries increasingly competitive in the market, selectively optimizing reactions and reducing the environmental impact of the production processes of these bioproducts. The present review addresses the primary methods for extracting and processing hemicelluloses from BSG using either biocatalysts (enzymes) or homogenous (acids, alkali, and salts) and heterogenous catalysts (solid acids and metal oxide) that can be used to pretreat the biomass and obtain the preferred byproducts. The state of the art of optimized catalysis mechanisms is also presented.

Effect of bamboo particle blending system on the properties of its composites

AbstractBamboo scrimber and carbonized bamboo scrimber are new green and sustainable materials that have recently gained widespread attention and application in construction and other fields. However, their production is accompanied by the generation of a large number of residues, such as bamboo particles (BPs) and carbonized bamboo particles (CBPs). In this study, we used BPs and CBPs as reinforcing phases and phenol‐formaldehyde (PF) resin, which is mainly used to manufacture bamboo scrimber, as the matrix to prepare bamboo particle composites (BPCs). The physical, flexural, and thermal properties of the composites were characterized, and the activation energies were analyzed and compared using Kissinger and Flynn–Wall–Ozawa (FWO) methods. The results showed that the blending system composed of two types of bamboo processing residues demonstrated significant composite performance enhancement. The BPC performance met the standard requirements for furniture particleboard, and the potential exists to further improve its thermal properties. This study fills the current gap in the kinetic analysis of BPCs and contributes to the further understanding and application of this material, thus facilitating the industrial use of bamboo processing residues and bamboo scrimber for sustainable development and economic benefits.

Evaluation of the toxicity of textile effluent treated by electrocoagulation

Abstract Textile effluents are complex, making it difficult to choose an effective treatment. The textile effluent toxicity in Lactuca sativa after pulsed current (PC) electrocoagulation (EC) was evaluated in this study. The EC was performed using 304 stainless steel electrodes in batch mode. Parameters monitored included pH, temperature, color, and turbidity. Additionally, the process residue was subjected to energy-dispersive X-ray fluorescence (XFR) to determine the elements present. The process achieved proportional color and turbidity removal ranging from 97 to 99% and from 74 to 85%, respectively. Chemical oxygen demand (COD) and total nitrogen removal were 81 and 49%, respectively, in a 50 min time-lapse. The process generated approximately 1.7 kg of solid residue/m3 treated effluent. The XFR results revealed the presence, mainly, of Fe, Cr, and Ni ions in the residue, as well as chlorine. The germination index (GI) and relative growth values showed that EC reduced effluent toxicity slightly, indicating the need for complementary treatment.

Water/acid/reductive biomass leaching of Cr(VI) in chromium ore processing residue (CORP) for safe discharge of effluent and to recover Cr(III) and gypsum

The hydrolyzed biomass, a green and renewable resource, was used as a reducing agent to achieve the harmless treatment of chromium ore processing residue (COPR). This paper proposes a detoxification process of two-stage sulfuric acid leaching accompanied by biomass reduction of hexavalent chromium and a one-step combined leaching and reduction process. The orthogonal tests and single factor tests allowed to propose the most suitable operating conditions of different stages such as biomass hydrolysis, two-stage acid leaching, reduction of the acid leachate and combined leaching and reduction. The Cr(VI) content in both the leach residue and reduction solution reached the discharge criterion. The FTIR and XPS measurements showed that the reducing sugars produced by the hydrolysis of biomass reacted with the leached Cr(VI) to generate chromium sulfate adsorbed on the surface of COPR. In addition, XRD, SEM-EDS showed that the gypsum was generated after COPR detoxification, which can be used for resource utilization, providing a new idea and reference for the harmless treatment of COPR producing Cr(III) and gypsum.