Publications

High-efficiency recycling method for Mo and Ni from spent catalyst via soda roasting and solvent extraction

The catalyst Mo–Ni/Al2O3 is commonly used in the hydrodesulfurization of petroleum fractions. The catalyst is discarded when its catalytic activity does not meet the requirement of the process, and the spent catalyst is usually classified as hazardous waste due to its significant heavy-metal content. The spent catalyst usually has a high commercial recovery value as a secondary resource for high-value metals, but the simple and high efficiency recovery method is still lacking. A high-efficiency recovery method for Mo and Ni from spent Mo–Ni/Al2O3 catalyst via soda roasting and solvent extraction was developed in this study. MoO3 interacts with Al2O3 and forms a new phase, Al2(MoO4)3, during blank roasting at 600–700 °C. Al2(MoO4)3 further transforms into NaMoO4 during soda roasting at 950 °C, and over 99.1% of Mo can be leached using hot water (60 °C). Solvent extraction with the trioctyl tertiary amine (N235) is employed to separate Mo from the leaching solution, and approximately 99.45% of Mo can be enriched through single-stage extraction. Around 99.2% of Mo can be stripped from loaded N235 using 8 M NH3•H2O. Further, PO4 3− and SiO3 2− can be removed from the stripping solution using Mg(NO3)2, and Mo is recycled in the form of MoO3, i.e., a product of the ammonium precipitation and calcining process. Over 99.3% of Ni can be leached from the solid residue using 30% volume fraction of H2SO4 and the solvent extraction can be enriched using diiso-octylphosphate (DP). Ni is finally recycled from the stripping solution as NiSO4•2H2O via evaporative crystallization. The total Mo and Ni recovery efficiencies of the newly developed integrated approach are 97.8% and 98.1%, respectively. Al is also recycled in the form of α-Al2O3 via chemical precipitation and calcination. The proposed approach is simple, with a high recovery rate and high selectivity, and can be applied to the recycling and disposal of spent Mo–Ni/Al2O3 catalyst.

Solidification/stabilization of municipal solid waste incineration (MSWI) fly ash during fired brick manufacturing by pelleting confinement and phase transformation

The primary challenge in incorporating municipal solid waste incineration (MSWI) fly ash into the production of fired brick lies in enhancing the solidification and stabilization of chlorides and heavy metals. This study proposed a novel method to suppress the evaporation and leaching of Cl salts and heavy metals by confining MSWI fly ash in pellets and incorporating Cl salts into stable Cl-containing phase. The palletization process of MSWI fly ash before mixing clay to mold raw brick could effectively reduce the volatilization and leaching of Cl salts and improve the mechanical strength of the brick. Moreover, the addition of glass powder during pelleting MSWI fly ash further enhanced the physical-mechanical properties of bricks and substantially reduced the leaching risks of Cl salts and heavy metals. Specifically, Cl volatilization and leaching ratios were reduced by 31.09–48.11 % and 18.13–30.99 %, Cl solidification efficiency was increased over 93 %. The improvement in solidification/stabilization of Cl salts and heavy metals relies primarily on physical confinement into pellets and chemical transformation of into stable Cl-containing mineral phases (Ca10Si6O21Cl2 and Ca3SiO4Cl2). Anyway, pelleting mixtures of fly ash and glass powder is proved to enhance both the property performance and environmental safety of the bricks, which could be regarded as an efficient solution with the practical and theoretical significance for the utilization of fly ash in construction materials.

Effects of electroplating sludge introduction on the morphology, mineral phase and porosity evolution of fired clay bricks

The mixing of electroplating sludge in the manufacturing of fired clay products (brick or ceramics) is usually considered as the viable method to disposal of it. However, the introduction of electroplating sludge usually decreases compressive strength and promotes water absorption, which somewhat limits the application of products containing this sludge. In this study, influences of electroplating sludge introduction were examined in terms of microstructure, mineral phase and porosity, for explaining the change in the water absorption and compressive strength. The microstructure analysis showed that the morphology of bricks texture became rough and porous. The porosity of bricks increased remarkably due to the introduction of electroplating sludge. With 10 wt% of electroplating sludge being added, surface area, pore volume and pore size increased by 2, 4, 7, and 2.2 times comparing with there was no electroplating sludge added. Oppositely, prolonging firing time decreased significantly surface area, pore volume and pore size. The increase in pore volume can mainly be attributed to an increase in mesoporous. Additionally, XRD analysis showed that most of heavy metals would be incorporated into spinel structure, and most of spinel will be formed within 1 h. Both the enlarged pore and the formation of spinel are mainly responsible for the increase in water absorption and the decrease in compressive. This study given some possible explanations for the change in the water absorption and compressive strength when electroplating sludge was introduced for the manufacturing bricks or ceramics, and provided directions for finding possible solutions.

Fabrication of Porous Functional Monolithic Aerogels With High‐Temperature Insulating and EMI Shielding Properties From Spent Lead‐Acid Battery Anode

The safe disposal of lead‐acid batteries has emerged as a critical environmental challenge of global concern. The development of innovative treatment technologies is crucial for addressing the imminent surge in spent lead‐acid battery waste. This work presents an innovative strategy for fabricating porous functional monolithic aerogels (PFMA) derived from spent lead paste anode materials. PFMA was synthesized via a facile sol‐gel method by reacting spent lead paste anode material with AlCl 3 ·6H 2 O and C 8 H 12 O 8 Zr at a mild temperature (98 °C). Aluminum dihydrogen phosphate (AHP) was employed as an inorganic binder to enhance high‐temperature stability in the composite system. The as‐prepared PFMA exhibits a monolithic structure with excellent thermal insulation and good electromagnetic interference (EMI) shielding properties. The as‐synthesized PFMA exhibits a low thermal conductivity of 0.16 W/(m·k), demonstrating comparable thermal insulation performance to conventional refractory ceramic composites (Al 2 O 3 ‐ZrO 2 and Al 2 O 3 ‐Cr 2 O 3 ). When subjected to butane flame exposure (∼1300 °C) for 3 min, the 16 mm thick PFMA sample exhibited only a modest front surface temperature increase to 140 °C, demonstrating exceptional thermal insulation. Moreover, PFMA exhibits good EMI shielding performance in the range of 12–18 GHz, which corresponds to satellite and radar bands suggesting a promising potential application in this field.

Volatilization characteristic and solidification of Pb, Zn, Cd and as during cement kiln co-processing of solid waste

Cement kiln co-processing always became one of the predominate approaches to dispose hazardous solid waste containing heavy metals. The volatilization and morphology of heavy metals should be paid to more concern during the cement production due to the environmental risk of heavy metals. In this study, the volatilization characteristics and the solidification effect of heavy metals (Pb, Zn Cd and As) during cement kiln co-processing were explored by the lab and pilot scale experiments. At same experimental conditions, the volatilization rate followed as As > Pb > Cd > Zn. Both limestone and cement raw meal have been demonstrated the capability to mitigate the rates of heavy metal volatilization. Notably, cement raw meal displays a more pronounced effect compared to limestone in suppressing volatilization processes. Over 50% of heavy metals were transformed into residual state at 1400 °C, and Cd, As and Zn were easy to be solidified than Pb. A pilot scale experiment proved that more than 80% of heavy metals was solidified, and Zn reached nearly 100%. Moreover, around 80% of Cd, As and Zn were remained in clinker and the rest was distributed in kiln dust particles, only very few amount was released into the exhaust flue gas. This study provides a comprehensive and extensive understanding of the volatilization characteristics and migration patterns of heavy metals in the cement kiln environment. It offers theoretical support for the control of heavy metals during the co-processing of hazardous solid waste in cement kilns.

High thermally insulating and lightweight Cr2O3 − Al2O3 aerogel with rapid–cooling property

Advanced aerogel materials with lightweight, flame retardant, and rapid cooling properties are urgently needed as thermal insulators in harsh environments. Herein, Cr2O3 − Al2O3 aerogels (CrAAs) were fabricated through a simple method and an ambient pressure drying process. A large number of pores were produced in the microstructure of the sample by the carbonization of soluble starch during calcination. The porous structure decreases the density of the prepared CrAA (Cr2O3 − Al2O3 aerogel) to as low as 0.143 g cm−3, and increases the thermal conductivity to as high as 0.125 W m−1 K−1, indicating the good thermal dissipation and rapid cooling performance of the sample. The prepared CrAAs possess a variety of composite properties such as good flame retardancy, rapid cooling, and colour restore after flame is extinguished. Moreover, after being subjected to flame treatment at ∼ 1300 °C using a butane blowtorch for 5 min, the CrAAs can be rapidly cooled to about 39.2 °C in about 1–2 min. The mechanism of the rapid cooling property was herein analysed, and we anticipate the potential application of CrAAs in flame–retardant cooling coatings.

Upcycling discarded polyethylene terephthalate plastics into superior tensile strength and impact resistance materials with a facile one–pot process

Discarding PET plastic (dPET) causes serious environmental pollution and enormous fossil resources waste. Processing techniques have mainly focused on the conversion of dPET into monomers, with minimal reports highlighting their transformation into high–value materials. This work intends to transform dPET into a high–performance material with potential alternative value in harsh production environments. The soft and hard segments of the thermoplastic polyester elastomeric (TPEE) molecular structure are reacted and cross–linked with dPET using a facile one–pot process, and two main polymers, (C8H4O4)n and ((C16H18O4)0.76·(C4H8O)0.24)n are generated after the reaction. Through chemical reactions between TPEE and dPET, new characteristic products and chemical bond–crossing structures are formed, while the resulting product particles or multiple TPEE particles are anchored by the high viscosity of dPET, which endows the material with superior tensile strength (34.21 MPa) and impact resistance. The glass transition temperature (T g) of the material implies that neither the molecular chain nor the chain segments can move, while only the atoms or groups composing the molecule vibrate at their equilibrium positions. The development of this new treatment method may contribute to the reduction of environmental pollution and the improvement of the high–value conversion and utilization of dPET.

Effects of electric arc furnace slag on promoting quality and environmental safety of fired bricks incorporating municipal solid waste incineration fly ash

The introduction of municipal solid waste incineration fly ash (MSWIF) during manufacturing process of fired bricks is a promising disposal method. However, the quality of products is negatively reduced and environmental risk increased significantly with the addition of MSWIF. This study proposed a novel approach to enhance the quality and environmental safety of fired brick by adding electric arc furnace slag (EAFS) as the pore plugger, which could overcome disadvantages brought by the introduction of MSWIF. Results showed that linear shrinkage and bulk density increased with the addition of EAFS, while water absorption and apparent porosity are reduced by more than 50%. The fracture microstructure of fired brick changed from porous to smooth with the addition of EAFS. The thermal conductivity declined by 25% and 30% at 1050 and 950 °C, and compressive strength was enhanced by 50% with the addition of 30 wt% EAFS. The chemically combination reactions between raw materials, such as the formation of albite, are promoted remarkably with the addition of EAFS. The leaching concentrations of heavy metals are far lower than regulatory limitations and environmental safety are enhanced significantly. In all, the addition of EAFS can promote the quality and environmental safety of fired brick, and can be used as an effective way to solve problems caused by introducing heavy metal solid waste.

Effects of gamma-ray irradiation on leaching of simulated 133 Cs + radionuclides from geopolymer wasteforms

Leaching of simulated 133Cs+ radionuclides from geopolymer wasteforms was examined with regard to effects from gamma-ray irradiation. Specifically, the compressive strengths, microstructures, pore structures, and leaching resistance of geopolymer wasteforms before and after irradiation were characterized. The leaching experiments were performed by immersion of wasteforms in deionized water, ground water, and seawater. It was found that gamma rays did not produce significant morphological changes, except for changes in the pore size distribution. The cumulative leaching fraction of all the leachants from the irradiated samples increased relative to the non-radiated samples, particularly during long leaching periods (11–42days). These results, and those from a mercury intrusion porosimeter analysis, can be attributed to irradiation-induced changes in pore structure. All the leaching indexes were greater than the minimum acceptable value of 6.0 set by the American Nuclear Society Standards committee, which indicated that the fly-ash geopolymers are suitable for radionuclide immobilization. However, the effects of gamma-ray irradiation on the immobilization of radionuclides cannot be ignored.

Formation kinetics and reaction behavior of pentavalent chromium formed in the cement kiln co-processing of solid waste

Cement kiln co-processing is becoming the main strategy to dispose of hazardous waste containing Cr. A newly-discovered pentavalent Cr compound, which was proved to be formed during cement kiln co-processing of solid waste, is partly responsible for the water-soluble Cr released from the cement. However, the formation characteristics and the solubility of Cr(V) are still unclear to date. In this study, the reaction kinetics and further redox reactions of Cr(V) at high temperature were examined, and its crystal structure and solubility were also explored. At the temperature range of 1000–1200 °C, the formation rate of Ca5(CrO4)3O0.5 reached over 90 % within 10 min, and then slowly increased to near 100 % from 10 min to 10 h. shows that Ca5(CrO4)3O0.5 is formed by interface reaction at an early period, and by diffusion at a later period. The kinetic analysis indicates that Ca5(CrO4)3O0.5 is initially formed through an interface reaction and subsequently through diffusion. Ca5(CrO4)3O0.5 was identified and assigned as hexagonal crystal group (P63/m). Approximately 0.55 g and 0.15 g of Ca5(CrO4)3O0.5 dissolve in neutral water at 100 °C and 50 °C, and the concentrations of Cr(V) in water reach 550 and 150 mg/L, respectively. Additionally, this study finds that at the temperature range of 400–700 °C Ca5(CrO4)3O0.5 can be oxidized into CaCrO4, and at the temperature higher than 1400 °C, it can be further converted into Ca3(CrO4)2 and reduced into CaCr2O4. This study gives a deep insight into Cr oxidation-reduction reaction during thermal treatment of solid waste. These insights provide a comprehensive understanding of Cr oxidation-reduction reactions during the thermal treatment of solid waste, offering valuable guidance for waste management strategies.

Enhanced Thermal Hydrolysis of Sewage Sludge by Introducing Tannic Acid (TA)

Thermal hydrolysis is becoming a crucial approach to enhance the level of sewage sludge resource utilization. Introducing additives became the dominant way

Recycling of Ni from leached spent catalyst residue by H2SO4 leaching and solvent extraction: leaching kinetics, purification and product preparation

Spent hydrodesulfurization catalyst (HDS) is considered as the important secondary resource for Mo and Ni. The separation of Mo from HDS was usually conduc

Volatilization Characteristic of Chloride Salts During the Production of Fired Brick Under Different Atmospheres

The behavior of chloride (Cl) salts in high-temperature environments is critical for various industrial processes, including waste treatment and material synthesis. However, the influence of different atmospheric conditions on the volatilization and interaction of Cl salts with clay minerals remains poorly understood. Previous studies have primarily focused on individual salt types under limited conditions, leaving a gap in the comprehensive understanding of how atmosphere composition affects Cl salt volatilization at high temperatures. This work addresses this gap by systematically investigating the volatilization behaviors of NaCl, KCl, and CaCl2 in different atmospheres (air, N2(g), NH3(g), and H2O(g)) across temperatures from 750 to 1050 °C. The results revealed significant differences in volatilization rates, with H2O(g) atmosphere significantly enhancing Cl volatilization, especially for NaCl and KCl, while CaCl2 showed notably lower volatilization. N2(g) and NH3(g) atmospheres exhibit a similar, moderate effect on Cl volatilization, while the air atmosphere suppressed Cl volatilization due to the formation of stable oxide structures. Thermodynamic simulations confirmed the formation of HCl(g) as the primary volatile species, with metal cations forming stable silicates and feldspar compounds with clay minerals. DFT calculations highlighted that H2O(g) lowers the energy barrier for chloride salt decomposition, accelerating volatilization by weakening the bond between metal cations and Cl ions. These findings provide valuable insights into the impact of atmospheric conditions on the volatilization of Cl salts in high-temperature environments.

熱処理によるりん酸塩によるCr(VI)を含む固形廃棄物の無毒化【Powered by NICT】

One-step high-efficiency recovery of high-purity MoO3 from spent hydrodesulfurization catalyst by water-vapor enhanced sublimation process

Spent hydrodesulfurization (HDS) catalysts were considered as a vital secondary resource for precious metals like Mo. The current pyrometallurgy and hydrometallurgy usually exhibits the characteristic of remarkable high energy consumption and high secondary pollutions. This study proposes an innovative technique to recycling MoO3 from spent HDS catalyst by sublimation process at high temperature, which has notable advantages of zero wastewater-generation and zero chemical reagent consumption. Notably, MoO3 recovery efficiency was improved remarkably with the introduction of water-vapor. About 99.33 % of MoO3 was recovered by heating spent HDS catalyst at 1100℃ for 2.5 h in water-vapor atmosphere with partial pressure of 101.33 kPa. The yielded MoO3 was tested with the purity of 99.94 % and exhibited the appearance of thin strips. Furthermore, the sublimation kinetic of MoO3 in air was adhered to a desorption model, while agreed with a non-desorption model in water-vapor atmosphere. Density Functional Theory (DFT) calculations revealed that -OH obtained by the dissociation of H2O molecules preferably combined with MoO3 and formed the volatile MoO3-OH, which was responsible for enhancing MoO3 sublimation efficiency significantly in water-vapor atmosphere. Economic analysis suggested that the direct cost of this method was 345 $/t, accounting for around 50 % compared to current roasting-leaching-purification methods. Overall, MoO3 sublimation enhanced by water-vapor atmosphere can be considered as a high-efficient and environmental-friendly approach for Mo recovery from spent catalysts.

A comparison study of three fluxing agents in promoting properties and environmental safety of bricks incorporating hazardous waste

The incorporation of hazardous solid waste in fired bricks fabrication is a viable way. However, the physical and mechanical properties of products were negatively influenced due to the involvement of hazardous solid waste. Three fluxing agents, waste glass powder (WGP), Na-feldspar and K-feldspar, were introduced in this study to eliminate these negative influences. Physical and mechanical properties were tested by standard method. Microstructure and pore structure of bricks were conducted by Scanning Electron Microscopy (SEM) and nitrogen adsorption and desorption isotherm. The change in mineral phase was detected by X-Ray Diffraction (XRD). The leaching toxicity of heavy metals were carried out by Toxicity Characteristic Leaching Procedure (TCLP) and Netherlands tank leaching test. The introduction of fluxing agents can greatly promote effectively compressive strength and decline water absorption. When 30 wt% (weight percent) of fluxing agents are added, water absorption reduced by more than 50%, and compressive strength increased by more than one time. XRD and SEM analysis showed that fluxing agents can promote the formation of glass-ceramic phase, which were mainly formed by the self-melting reaction of fluxing agents and the interaction with silicon-aluminium oxides. These dense glass phases could reduce the porosity and promote the compactness of microstructure. The formation of glass-ceramic phases could also reduce the leachability risk of heavy metals. Combing with properties of brick and price of fluxing agents, WGP is considered to be more suitable for improving properties of fired bricks containing hazardous waste. This study could provide some useful parameters and knowledge for improving properties and leaching toxicity risk when hazardous wastes were utilized in the production of fired brick.

Kinetics study and bio-phase characteristics of drainage in paddy fields purified by a compound ecological ditch

Paddy field drainage discharged directly into natural waters without the treatment will aggravate water eutrophication. The removal characteristics of the

Addition of waste glass for improving the immobilization of heavy metals during the use of electroplating sludge in the production of clay bricks

A novel strategy for improving the immobilization of heavy metals during the use of electroplating sludge in the production of clay bricks, was proposed by the addition of waste glass. Waste glass addition reduced open porosity and surface area, and enhanced compressive strength remarkably. With the adding amount of waste glass powder up to 30 wt.%, surface area and open porosity declined from 0.84 to 0.05 m2/g and from 10.69 to 1.16%, respectively. Compressive strength increased from 20 to 32.7 MPa. Moreover, the leaching concentration of heavy metals decreased considerably and met the regulation standard. Heavy metals, Cu and Zn, have been incorporated into stable spinels phase and adding waste glass was favored to the formation of spinel. It was regarded that waste glass and andesine melted and formed liquid phase during firing process, which improved the mass transfer and the reaction kinetic of spinels formation. The liquid phase filled in the pores and densified bricks body, which also play a important role in preventing heavy metals from releasing. Overall results suggested the addition of waste glass powder was a promising method in improving immobilization of heavy metals during the use of electroplating sludge in production of clay bricks.