•The technique with oxygen control under vacuum condition was used for the first time to remove tin in crude lead.•Detinned lead (Sn < 3 ppm) was obtained by using air as oxidizing agent.•The reaction system was under a vacuum, which resulted in little Pb-loss and the dusty slag was kept in the reactor thereby creating a good work environment.Conventional detinning process of lead bullion usually includes the following problems: the oxidizing refining process takes a long time to finish the oxidation of tin and products mass slag, while the basic refining process consumes large reagent, and the labor condition is poor. Therefore, a novel technique with oxygen controlled under vacuum condition for removing tin in crude lead was investigated, which shows characters such as, low-energy consumption, less metal wastage and environmental friendly. During this process, tin was removed from lead bullion by converting to tin oxide and concentrating in the dross. The experimental results showed that the residual Sn-concentration in detinned lead was about 2 ppm corresponding to the lead loss ratio about 2–3 wt% under the following experimental conditions: temperature of 750 °C, oxidation time of 80 min, agitation speed of 100 rpm and air flow rate of 60 mL/min corresponding to the residual gas pressure of 57 KPa.

•Final pyrolysis temperature has a greater influence than holding time in general.•The volatiles were mainly formed between 300 and 500 °C in the co-pyrolysis process.•Noncondensable gases (CO2, CO, CH4, etc.) were the main components after 500 °C.Vacuum co-pyrolysis of Chinese fir sawdust (CFS) and waste printed circuit boards (WPCBs) at different heating conditions were examined in this paper. The composition of the pyrolysis oils was analyzed by gas chromatography–mass spectrometry (GC–MS). It was found that the content of most of the compounds with relatively long molecular chain had a higher value at relatively low temperature (400–600 °C) and short holding time (10 min), and decreased at relatively high temperature (800 °C) and long holding time (30–90 min); while the content of most of the compounds with relatively short molecular chain presented an adverse trend. The co-pyrolysis process was also analyzed by thermogravimetric (TG) analysis with evolved product analysis by Fourier transform infrared (FTIR) spectroscopy. The results showed that the volatiles were mainly generated between 300 and 500 °C, and after 500 °C, noncondensable gases (CO2, CO and CH4) were the main components in the pyrolysis process.

•Three-step vacuum distillation was employed for treating arsenic sulphide residue.•S8 and As2O3, arsenic sulfide, PbS were evaporated out as distillate respectively.•CaF2 was left behind as the third distilland after three-step vacuum distillation.•Almost 100 wt.% of arsenic can be removed from arsenic sulphide residue.Up to now, most of arsenic sulphide residue can't be properly disposed. The traditional processes for treating arsenic sulphide residue have some widespread drawbacks such as the complex process, the high cost in operation, and the less than satisfactory removal effect and environmental protection. In view of this, a process of three-step vacuum separation was proposed for treating arsenic sulphide residue in this work. During vacuum separation, elemental sulphide and arsenic trioxide could be recovered effectively in primary distillation at temperature of 180 °C, distillation time of 2.0 h, corresponding to the residual gas pressure of 15 Pa. In secondary distillation, arsenic sulfide was obtained under the condition of 450 °C for 30 min, with a residual gas pressure of 15 Pa. When the temperature increased to 1000 °C for 2 h, lead sulfide was evaporated out in third distillation. Through the three-step vacuum separation, calcium fluoride was left behind in the third distilland, in which the content of arsenic was 5.65 × 10−4 wt.%. Correspondingly, the removal rate of arsenic was almost 100%. The vacuum process is expected to be effectively employed for recycling valuable components from arsenic sulphide residue, and meanwhile eliminating its pollution.

•Co-pyrolysis process presents antagonistic effect in the yields of the volatiles.•Co-pyrolysis process is good for the formation of brominated aromatic compounds.•The volatiles were mainly formed between 300 and 450 °C in the pyrolysis process.•Noncondensable gases (CO2, CO, CH4, etc.) were the main components after 450 °C.•Co-pyrolysis oils show better synthetic properties than the separate ones.Vacuum co-pyrolysis of Chinese fir sawdust (CFS) and waste printed circuit boards (WPCBs) at different mass ratios were examined in this paper. The structures and contents of the pyrolysis oils were analyzed by Fourier transform infrared (FTIR) spectroscopy and gas chromatography–mass spectrometry (GC–MS). The results showed that co-pyrolysis processes presented antagonistic effect in the yield of the total volatiles (liquid plus gas) at the experimental conditions, but it is beneficial to the formation of brominated aromatic compounds (whose total content in WPCBs pyrolysis oil was only 6.51 wt%, while in co-pyrolysis processes (CFS/WPCBs = 4:1, 1:1, 1:4), they were 10.96 wt%, 7.98 wt% and 14.84 wt%, respectively). The co-pyrolysis processes were also analyzed by thermogravimetric (TG) analysis with evolved product analysis by FTIR. The results showed that the volatiles were mainly formed between 300 and 450 °C, and after 450 °C, there were mainly some noncondensable gases (CO2, CO and CH4) formed.

So far, conventional processes that have been employed to delacquer the paints decorated on used beverage cans (UBCs) are less than satisfactory in economic and environmental effect. Therefore, a new method combining vacuum pyrolysis with dilute sulfuric acid leaching to delacquer the paints was investigated. The results of vacuum pyrolysis showed that the decoating rate increased with the increase of temperature and the paints were almost 100% removed from UBCs under the following conditions: temperature of 650 °C, holding time of 20 min, and residual gas pressure lower than 0.1 kPa. The pyrolysis oil was mainly composed of phenol and 2-methy-phenol analyzed by GC-MS. The delacquered UBCs were subsequently leached with 5% H2SO4 for 60 s and TiO2 was recovered by calcining the residuals in muffle furnace at 450 °C for 15 min. This innovative technology offers an effective method to delacquer paints from UBCs, which obtains excellent stripping effect and avoids the production of toxic substances generated in direct combustion process. Furthermore, the pyrolysis oil can be reused as chemical feedstock in other fields.

A vacuum evaporation technology for treating antimony-rich anode slime was developed in this work. Experiments were carried out at temperatures from 873 K to 1073 K and residual gas pressures from 50 Pa to 600 Pa. During vacuum evaporation, silver from the antimony-rich anode slime was left behind in the distilland in a silver alloy containing antimony and lead, and antimony trioxide was evaporated. The experimental results showed that 92% by weight of antimony can be removed, and the silver content in the alloy was up to 12.84%. The antimony trioxide content in the distillate was more than 99.7%, and the distillate can be used directly as zero-grade antimony trioxide (China standard).

In crude lead or copper electrorefining, the by-product anode slime is an important material of recycling precious metals. However, the existing methods for treating arsenic-rich anode slime are less than satisfactory not only for the removal effect of arsenic but also for the environment protection. Therefore, a new technology for treating arsenic-rich anode slime was proposed in this paper, namely the two-step process of vacuum dynamic evaporation (VDE) and vacuum dynamic flash reduction (VDFR). Through this two-step process, silver from the anode slime was left behind in distilland as the silver alloy, and the trivalent oxide of arsenic was evaporated in the distillate. The experimental results showed that the removal ratio of arsenic was 99.96%. Moreover, these vacuum technologies offer improvements in metallurgical and environmental performance.Highlights► Arsenic can be satisfactorily removed from anode slime by two-step vacuum methods. ► Silver from anode slime was left behind in the distilland as the silver alloy. ► Impurity elements including arsenic and antimony were evaporated in the distillate. ► Vacuum methods eliminate much of the air pollution and metal losses.

Anode slime is an important material of recycling precious metals. Up to now, treating the arsenic- and antimony-rich anode slime by conventional processes has the following problems: its economic and environmental effect is less than satisfactory, and the removal effect of arsenic and antimony from anode slime in present processes is not all that could be desired. Therefore, vacuum dynamic flash reduction, a new process for treating arsenic- and antimony-rich anode slime, was investigated in this work. During vacuum dynamic flash reduction, silver from the arsenic- and antimony-rich anode slime was left behind in the distilland as the silver alloy, and trivalent oxides of arsenic and antimony were evaporated in the distillate. The experimental results showed that the evaporation percent of the arsenic- and antimony-rich anode slime was 65.6%. Namely, 98.92% by weight of arsenic and 93.67% by weight of antimony can be removed under the following experimental conditions: temperature of 1083 K, vacuum evaporation time of 60 min, and air flow rate of 400 mL/min corresponding to the residual gas pressure of 250 Pa. Moreover, vacuum treatment eliminates much of the air pollution and material losses associated with other conventional treatment methods.

Doehlert matrix was used to optimize the experimental conditions for the preparation of activated carbons from herb residues by vacuum chemical activation and traditional chemical activation using ZnCl2 as activation agent. The effects of activation temperature and impregnation ratio, the most influential factors of ZnCl2 chemical activation, were studied. The obtained activated carbons were characterized by total yield and methylene blue and iodine adsorption value. Each response has been described by a second-order model, and the predicted model presented a good agreement with experimental data. The results showed that activated carbons prepared by vacuum chemical activation have higher yield and better adsorption capacity. The removal percentages of methylene blue for the two optimal activated carbons and a commercial activated carbon were determined. The activated carbon prepared by vacuum chemical activation exhibited the highest methylene blue removal efficiency.

Activated carbons especially used for gaseous adsorption were prepared from Chinese fir sawdust by zinc chloride activation under vacuum condition. The micropore structure, adsorption properties, and surface morphology of activated carbons obtained under atmosphere and vacuum were investigated. The prepared activated carbons were characterized by SEM, FTIR, and nitrogen adsorption. It was found that the structure of the starting material is kept after activation. The activated carbon prepared under vacuum exhibited higher values of the BET surface area (up to 1079 m2 g−1) and total pore volume (up to 0.5665 cm3 g−1) than those of the activated carbon obtained under atmosphere. This was attributed to the effect of vacuum condition that reduces oxygen in the system and limits the secondary reaction of the organic vapor. The prepared activated carbon has well-developed microstructure and high microporosity. According to the data obtained, Chinese fir sawdust is a suitable precursor for activated carbon preparation. The obtained activated carbon could be used as a low-cost adsorbent with favorable surface properties. Compared with the traditional chemical activation, vacuum condition demands less energy consumption, simultaneity, and biomass-oil is collected in the procedure more conveniently. FTIR analysis showed that heat treatment would result in the aromatization of the carbon structure.

The preparation of activated carbon from Chinese fir sawdust by zinc chloride activation under both nitrogen atmosphere and vacuum conditions was carried out in a self-manufactured vacuum pyrolysis reactor. The effects of the system pressure and the activation condition (nitrogen or vacuum) on pore development were investigated. The results show that both high quality activated carbon and high added-value bio-oil can be obtained simultaneously via vacuum chemical activation. The characteristics of the activated carbons produced under vacuum conditions are better than those prepared under nitrogen atmosphere. The performance parameters of the activated carbon obtained under vacuum conditions are as follows: the pore size distribution is mainly microporous, the Brunauer-Emmett-Teller (BET) surface area is 1 070.59 m2/g, the microporous volume is 0.502 4 cm3/g, the average pore size is 2.085 nm, and the iodine adsorption value and the methylene blue adsorption value are 1 142.92 and 131.34 mg/g, respectively. The activated carbon from vacuum chemical activation has developed micropores, and the N2 adsorption equilibrium constant of the corresponding activated carbon gradually increases with the decrease of reaction system pressure.

•Vacuum thermal reduction avoided the harm of lead particulates in the reduction process.•Hydrometallurgical desulfurization solved the problem of the emission of sulfur dioxide to the atmosphere.•The vacuum thermal recovery process of lead has the potential of economic and ecological benefits.Lead sulfate, lead oxides and lead metal are the main component of lead paste in spent lead acid battery. When lead sulfate was desulfurized and transformed into lead carbonate by sodium carbonate, lead metal and lead oxides remained unchanged. Lead carbonate is easily decomposed to lead oxide and carbon dioxide under high temperature. Namely, vacuum thermal process is the reduction reaction of lead oxides. A compatible environmental process consisted of hydrometallurgical desulfurization and vacuum thermal reduction to recycle lead was investigated in this research. Lead paste was firstly desulfurized with sodium carbonate, by which, the content of sulfur declined from 7.87% to 0.26%. Then, the desulfurized lead paste was reduced by charcoal under vacuum. Under the optimized reaction conditions, i.e., vacuum thermal reduction at temperature 850 °C under 20 Pa for 45 min, a 22.11 × 10−2 g cm−2 min−1 reduction rate, and a 98.13% direct recovery ratio of fine lead (99.77%) had been achieved, respectively.

Waste lead storage battery is the most important recyclable lead material not only in various European and other OECD countries but also in China. Pollution control of lead has become the focus of people’s attention in the world. A vacuum process for recycling waste lead storage battery was developed in this work. The experimental results showed that all the valuable materials in waste lead storage battery could be satisfactorily recycled by vacuum technologies. The vacuum melting of lead grids and the vacuum reduction of lead pastes produce the lead bullion with the direct recovery ratio of 96.29% and 98.98%, respectively. The vacuum pyrolysis of plastics can produce pyrolysis oil with yield of more than 93 wt.%. These vacuum recycling technologies offer improvements in metallurgical and environmental performance.

Here, we focused on the recycling of waste printed circuit boards (WPCBs) using vacuum pyrolysis-centrifugation coupling technology (VPCT) aiming to obtain valuable feedstock and resolve environmental pollution. The two types of WPCBs were pyrolysed at 600 °C for 30 min under vacuum condition. During the pyrolysis process, the solder of WPCBs was separated and recovered when the temperature range was 400–600 °C, and the rotating drum was rotated at 1000 rpm for 10 min. The type-A of WPCBs pyrolysed to form an average of 67.91 wt.% residue, 27.84 wt.% oil, and 4.25 wt.% gas; and pyrolysis of the type-B of WPCBs led to an average mass balance of 72.22 wt.% residue, 21.57 wt.% oil, and 6.21 wt.% gas. The GC–MS and FT-IR analyses showed that the two pyrolysis oils consisted mainly of phenols and substituted phenols. The pyrolysis oil can be used for fuel or chemical feedstock for further processing. The recovered solder can be recycled directly and it can also be a good resource of lead and tin for refining. The pyrolysis residues contained various metals, glass fibers and other inorganic materials, which could be recovered after further treatment. The pyrolysis gases consisted mainly of CO, CO2, CH4, and H2, which could be collected and recycled.Highlights► An efficient recovery technology of WPCBs (vacuum pyrolysis-centrifugation coupling technology (VPCT)) is first put forward. ► Vacuum technology was used to enhance the process of pyrolysis of organic resin and separation of volatile compounds. ► The organic resin, glass fiber and metal were separated simultaneously by VPCT. ► A new equipment of recycling of WPCBs is exploited, which can separate solder and pyrolyze organic materials simultaneously. ► Two kinds of vacuum pyrolysis products of WPCBs were characterized and the utilization methods of them were made.

Spent lithium-ion batteries containing lots of strategic resources such as cobalt and lithium are considered as an attractive secondary resource. In this work, an environmentally compatible process based on vacuum pyrolysis, oxalate leaching and precipitation is applied to recover cobalt and lithium from spent lithium-ion batteries. Oxalate is introduced as leaching reagent meanwhile as precipitant which leaches and precipitates cobalt from LiCoO2 and CoO directly as CoC2O4·2H2O with 1.0 M oxalate solution at 80 °C and solid/liquid ratio of 50 g L−1 for 120 min. The reaction efficiency of more than 98% of LiCoO2 can be achieved and cobalt and lithium can also be separated efficiently during the hydrometallurgical process. The combined process is simple and adequate for the recovery of valuable metals from spent lithium-ion batteries.Graphical abstractDownload full-size imageHighlights► Vacuum pyrolysis as a pretreatment was used to separate cathode material from aluminum foils. ► Cobalt and lithium can be leached using oxalate while cobalt can be directly precipitated as cobalt oxalate. ► Cobalt and lithium can be separated efficiently from each other only in the oxalate leaching process. ► High reaction efficiency of LiCoO2 was obtained with oxalate.

•A synthetic mechanism for fluorine separation and removal is proposed.•Additives transform calcium fluoride into solubility compound.•Roasting and acid-leaching make fluorine removal feasible.•Beryllium ore was treatment under low temperature and less treating time.To avoid the influence of fluorine on the extraction of beryllium, separating fluorine from high-fluorine beryllium ore was discussed in this study. The factors affecting on fluorine removal, such as roasting temperature, roasting time, dosage of the additive in roasting process, and the variety and concentration of acid in the leaching process, were separately investigated. The intermediates and final products were identified by XRD. Under the following roasting and leaching conditions: heating temperature 800 °C, treatment time 120 min, additive dosage of Na2CO3 by 60% weight, leaching by distilled water at 50 °C for 30 min and acid (1.7 mol/L HNO3) at 60 °C for 60 min, the percentage of fluorine and beryllium oxide was 1.6%; heating temperature 800 °C, treatment time 180 min, additive dosage of Na3PO4 by 50% weight, leaching by distilled water at 50 °C for 30 min and acid (1.7 mol/L HNO3) at 60 °C for 60 min, the percentage of fluorine and beryllium oxide was 7.12%. Both of the results with additive Na2CO3 and Na3PO4 can meet the requirement of the industrial production of beryllium after the pretreatment, while Na2CO3 is more efficient. Results also indicated that nitric acid was more reactive than sulfuric acid.