Applications of molten salt and progress of molten salt electrolysis in secondary metal resource recovery

Molten salt is an excellent medium for chemical reaction,energy transfer,and storage.Molten salt innovative technologies should be developed to recover metals from secondary resources and reserve metals from primary natural sources.Among these technologies,molten salt electrolysis is an economic and environment-friendly method to extract metals from waste materials.From the perspective of molten salt characteristics,the application of molten salts in chemistry,electrochemistry,energy,and thermal storage should be comprehensively elaborated.This review discusses further directions for the research and development of molten salt electrolysis and their use for metal recovery from various metal wastes,such as magnet scrap,nuclear waste,and cemented carbide scrap.Attention is placed on the development of various electrolysis methods for different metal containing wastes,overcoming some problems in electrolytes,electrodes,and electrolytic cells.Special focus is given to future development directions for current associated processing obstacles.

Supply modes for renewable-based distributed energy systems and their applications:case studies in China

Distributed energy systems(DES),as an integrated energy system with coupled distributed energy resources,have great potential in reducing carbon dioxide emissions and improving energy efficiencies.Considering the background of urbanization and the energy revolution in China,the study investigates the renewable-based DESs supply modes and their application in China.A new method is proposed to classify DESs supply modes into three categories considering the renewable resource in domination,and their application domains are discussed.A comprehensive model is given for economic and environmental evaluation.Typical case studies show that the renewable-based DES systems can supply the energy in a cost-effective and environment-friendly way.Among them,the biomass waste dominated supply mode can not only achieve"zero"carbon emissions but also"zero"energy consumption,even though not yet economically attractive under the present policy and market conditions.Thus,recommendations are given to promote the further deployment of renewable-based DESs,regarding their supply modes,policy requirements,and issues to be addressed.

A promising method for recovery of LiMn_(2)O_(4) and graphite from waste lithium-ion batteries: Roasting enhanced flotation

In this study,a roasting enhanced flotation process was proposed to recover LiMn_(2)O_(4) and grapite from waste lithium-ion batteries(LIBs).The effects of roasting temperature and time on the surface modification was investigated,and a series of analytical technologies were used to reveal process mechanism.The results indicate that LiMn_(2)O_(4) can be effectively separated from graphite via flotation after the roasting.The flotation grade of LiMn_(2)O_(4) was significantly increased from 63.10%to 91.36%after roasting at 550℃for 2 h.The TG-DTG analysis demonstrates that the difficulty in flotation separation of LiMn_(2)O_(4) from graphite is caused by the organic binder and electrolytes coating on their surfaces.The XRD,SEM,XPS,and contact angle analyses confirm that the organic films on the surfaces of those materials can be effectively removed by roasting,after which the wettability of LiMn_(2)O_(4) is regained and thus the surface wettability difference between the cathode and anode materials is increased significantly.The closed-circuit flotation test indicates that a LiMn_(2)O_(4) sample with high grade of 99.81%is obtained,while the recovery of LiMn_(2)O_(4) is as high as 99.40%.This study provides an economical and eco-friendly way to recycling waste LIBs.

Tin recovery from a low-grade tin middling with high Si content and low Fe content by reduction–sulfurization roasting with anthracite coal

A new method for separating and recovering tin from a low-grade tin middling with high Si content and low Fe content by roasting with anthracite coal was researched by studying the reaction mechanism and performing an industrial test,in which the Sn was sulfurized into SnS(g)and then collected using a dust collector.The Fe–Sn alloy may be formed at roasting temperatures above 950°C,and like the roasting temperature increases,the Sn content and Sn activity in this Fe–Sn alloy decrease.Also,more FeS can be formed at higher temperatures and then the formation of FeO–FeS with a low melting point is promoted,which results in more serious sintering of this low-grade tin middling.And from the thermodynamics and kinetics points of view,the volatilization of the Sn decreases at extremely high roasting temperatures.The results of the industrial test carried out in a coal-fired rotary kiln show that the Sn volatilization rate reaches 89.7%and the Sn is concentrated in the collected dust at a high level,indicating that the Sn can be effectively extracted and recovered from the low-grade tin middling with a high Si content and low Fe content through a reduction–sulfurization roasting process.

Redox behavior of indium in molten chlorides

An electrochemical study on the redox behavior of indium in the eutectic LiCl-KCl system at 450 ℃ was carried out with the transient techniques of cyclic voltammetry and chronopotentiometry on an inert molybdenum electrode. The reduction of In(Ⅲ) was found to be a two-step process involving In(Ⅲ)/In(Ⅰ) and In(Ⅰ)/In couples at the potentials of about-0.4 and-0.8 V versus Ag/AgCl, respectively. The redox mechanism was further confirmed by the theoretical evaluation of the number of transferred electrons based on cyclic voltammetry and characterizations of the precipitates generated by the potentiostatic electrolysis. The diffusion coefficients of indium ions in the eutectic LiCl-KCl melt at 450 ℃ were estimated by cyclic voltammetry and chronopotentiometry. The results obtained through the two methods are in fair agreement, delivering an average diffusion coefficient of approximately 1.8×10^(-5)cm^(2)/s for In(Ⅲ), and 1.4×10^(-4)cm^(2)/s for In(Ⅰ).

The significance of resource recycling for coking wastewater treatment:based on environmental and economic life cycle assessment

The sustainability of the coking industry is supported by reasonable production profit and environmental quality requirements.The traditional measures substantially increased the related costs for enterprises to reach standards.This paper aims to develop a comprehensive cost combined environmental impact assessment method that is necessary for the analysis of wastewater treatment systems.Typical three coking wastewater treatment processes in China were evaluated.Results showed that eutrophication dominantly contributed to the overall environmental effect.Improving effluent quality could significantly reduce the total environmental impact.In terms of an economic perspective,the price of raw materials was the main factor that affected the operating cost of comprehensive treatment.Based on subsystem analysis,the pretreatment stage accounted for the majority of environmental and cost burdens,respectively reaching 64%-78%and 64%-86%.Optimizing the pretreatment process by enhancing the efficiency of high concentration raw material recovery and substituting toxic raw materials for extractant could reduce the environmental impact and economic cost by 43.8%and 57%,respectively,which was an effective way to improve the potential performance of coking wastewater treatment plants(WWTPs).

Ginkgo Biloba Waste Resources and Waste Treatment Combined with Modern Progress and Development Model

Background:Ginkgo biloba L.is listed in the Red List of Endangered Species by the International Union for Conservation of Nature.G.biloba is an important medicinal plant in China and can be widely used in materials,gardens,and as a source of nutrients.With the large-scale planting of ginkgo plants,China,accounts for more than 70%of the world’s total gingko output.Currently,G.biloba P.E.is the main extract under product development and application.However,G.biloba has been discarded as waste for a long time and has not been well developed and utilized.According to incomplete statistics,nearly 40,000 tons are discarded in China every year,which not only wastes resources but also pollutes the environment.Objective:This is an issue of great significance and adds value to scientific research.We aim to develop a key technology for resource recycling by combining G.biloba waste resources and waste treatment.Methods:Data were obtained by searching databases such as CNKI,and analyzing the herb application,modern application,main chemical components,utilization of waste parts,ways and modes combined with waste treatment,and safety of G.biloba.This systematic analysis can serve as a reference for the recycling of waste resources in other fields.Conclusion:The chemical constituents of the outer seed coat of G.biloba mainly include hydrophenols,phenolic acids,and biflavones,among which the phenolic acid of G.biloba can be used to extract glycolic acid,which can inhibit Mycobacterium tuberculosis.The domestic waste produced by tuberculosis(TB)patients contains a large number of bacilli,and the incidence of transmission can be reduced by using glycolic acid to inhibit the growth of TB bacilli in the waste.

Process of Re-Resourcing of Converter Slag

The process of ＂re-resourcing of converter slag＂ was put forward based on the analysis of the existing steel slag treatment process.The converter slag obtained from Jinan steel plant was studied.After grinding,the slag contained 3.3% of iron particles,54.84% of magnetic part（wTFe=20%）,and 41.84% of non-magnetic part,which could be used for making cement directly.At a temperature below 1000 ℃,the non-magnetic Fe2O3 in the slag could be efficiently reduced to magnetic iron by pure H2 and CO.The slag after precise reduction had high degree of dispersion and did not get sintered,which provided an optimum condition for the separation of iron and impurities.To separate the slag and enrich the iron after reduction,the laboratory-scale device of magnetic separation was designed and made.The process of slag re-resourcing,which included magnetic sorting,precise reduction,magnetic separation,and removal of free calcium oxide（f-CaO）,was proposed to obtain iron-rich magnetic materials and cement adulterant materials.Through this process,33 kg iron particles,150 kg iron-rich material and 700 kg cement could be obtained in each ton slag.Besides,this process to recycle converter slag had a lower energy and material consumption and no pollutant emission.

Coal fly ash reinforcement for the property enhancement of crude glycerol-based polyurethane foam composites

Coal fly ash(CFA)is the main combustion residue of fine ground coal in the process of coal-fired thermal power generation,and crude glycerol(CG)is the byproduct of biodiesel production.The novel polyurethane/CFA(PU/CFA)foam composites were prepared from CFA and CG.Two kinds of CFA,CFAI and CFAII were used as fillers for the property enhancement of PU/CFA composites,and the effects on foaming behavior and the reinforcement for the PU/CFA composites were investigated.It was found that the addition of CFA can prolong the rising time and tack-free time,and the maximum rising time and tack-free time increased to 40 s and 42 s.Meanwhile,the maximum compressive strength of PU/CFAI and PU/CFAII increased to 0.2186 MPa and 0.2284 MPa with the addition of CFA.The thermogravimetric analysis showed that the PU/CFA composites underwent three stages of thermal decomposition,and the amount of carbon residue increased from 23.11%to 67.91%with increasing CFA dosage.Moreover,the values of the limit oxygen index increased from 21.5%to 23.7%with the incorporation of CFA into the PU foam matrix,indicating that CFA improved the thermal stability and flame retardant performance of the composites.This study provided a new method for the recycling and high-value utilization of CG and CFA.

A compartment model and numerical analysis of circulatory economy

This paper describes an industrial structure and its equation system of a circular economy for material circulation and builds a system dynamic model for resources recycling utilization based on Compartment Model Theory.A circulation multiplier and its computational formula are defined for measuring the efficiency of resources recycling utilization.The simulated results indicate that the resources recycling utilization can not only realize the amount accumulation of natural resources and improve the resources recycling efficiency but can minimize discharges into natural environment by means of adjustment to each compartment parameter in the circular economy.