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The present study reports a sequential, non-acid process for effective recovery of copper and precious metals from mobile phone printed circuit boards. In this process, gold and silver were first enriched during the synthesis process of cuprous chloride and then leached by thiosulfate method. Results indicated that the distribution of gold and silver in the liquid and solid phases during the synthesis of cuprous chloride process was affected by the [Cu]/[Cu

Facile fabrication of porous carbon materials from waste halogenated plastic is highly attractive but frequently hampered due to potential release of halogenated organic pollutants. In this study, a novel type of carbon hybrid was tentatively synthesized from a real-world halogenated plastic as an inexpensive carbon source by sub/supercritical carbon dioxide carbonization technique. It was found that halogen-free carbon carrier was advantageously synthesized through carbonization of halogenated plastic without using catalysts due to zip depolymerization, random chain cracking and free radical reactions induced by sub/supercritical carbon dioxide technique. Exhibiting with more abundant functional groups including C-O, CO groups than pyrolytic carbon carrier, the derived carbon carrier demonstrated excellent performance in selective recovery of lithium from cathode powder with highest recovery efficiency of 93.6%. Mechanism study indicated that cathode powder was transformed into low-valence states of transition metals/metal oxides and released lithium as lithium carbonate due to collapse of oxygen framework via carbothermic reduction. This work provides an applicable and green process for synthesis of alternative carbon carrier from waste halogenated plastic and its application as carbothermic reductant in lithium recovery.

Recycling of spent Li-ion batteries is crucial for achieving sustainable development of battery industry. Current recycling processes mainly focus on valuable metals but less attention has been paid to spent graphite, which generally ends up as secondary waste. In this study, a process for preparing graphene and recovering Li in anode as a by-product from spent graphite was developed. The key point was to re-charge the spent LIBs to generate lithium graphite intercalation compounds. The lithium graphite intercalation compounds were then subjected to a hydrolysis procedure and graphene could be produced through ultrasonic treatment via the expansion/micro-explosion mechanism. Experimental results demonstrated that 1–4 layered graphene could be efficiently produced when spent Li-ion batteries with beyond 50% capacity were re-charged. The prepared graphene showed high quantity containing few defects (ID/IG = 0.33, C/O = 13.2 by energy dispersive spectroscopy and C/O = 8.8 by X-ray photoelectron spectroscopy). In addition, Li was simultaneously recovered in the form of battery-grade lithium carbonate in the above process. Economic analysis indicated that the graphene production cost was extremely low ($540/ton) compared to that of commercial graphene.

Upcycling of waste plastics as functional materials is a new approach for synthesizing low-cost and durable adsorbents with zwitterionic property. Herein, a facile process for recycling blending waste plastics to fabricate zwitterionic plastic-g-hydrogel (ZPH) for simultaneous adsorbing cationic and anionic heavy metals was developed. ZPH possessed high affinities for cations and anions in both acid and alkaline conditions owing to its zwitterionic property, and the maximum adsorption capacities of Pb

Recycling of spent lithium-ion batteries (LIBs) has aroused extensive attentions with the expanding demand of electric vehicles. Two considerable challenges of LIBs recycling were separating electrode materials from metallic foils and reclaiming hazardous electrolyte. In the current study, an environmentally benign process was developed to recovery electrode materials and hazardous electrolyte. The main merits were that no strong acid or alkali was applied in the process, and the electrode materials were reclaimed in flaky form. A special complex aqueous peeling agent, namely exfoliating and extracting solution (AEES) was manufactured and applied in the process. The results indicated that cathode material could be exfoliated from Al foil by weakening the mechanical interlocking force and Coulomb force between cathode materials and foils. Ethylene carbonate (EC) and propylene carbonate (PC) could be extracted from electrodes and separators and recovered via distillation. LiPF6 could be precipitated from EC and PC and recovered via filtration. The conditions could be precisely controlled by optimizing the concentration of AEES. The recovery efficiencies of electrolyte, Al foil, Cu foil and electrode materials were 95.6%, 99.0%, 100% and near 100%, respectively. The process efficiently avoided infiltration of impurities into the electrode materials and is environmentally friendly for industrial application.

Hypersaline wastewater is a typical industrial wastewater produced by iron and steel metallurgy, food material processing and other industries. Aiming at a waste liquid produced by mechanical vapour recompression evaporation and concentration in Tianjin coastal industrial zone, an environment-friendly supercritical water oxidation technology was used to efficiently remove the high-content organic matter in the hypersaline wastewater concentrate (HWC). A comparison of the degradation effects of various oxidants in the supercritical state showed that hydrogen peroxide (H2O2) could be used as a suitable agent for processing the HWC. The reaction parameters were systematically optimised by single-factor experiment and response surface design. The degradation mechanism and reaction characteristics were analyzed using gas chromatography mass spectrometry. Solid residues were characterised by field emission scanning electron microscope. The results indicated that when the dosage of hydrogen peroxide was 6.39%, the reaction temperature was 380��C, the reaction time was about 90 min and the optimal total organic carbon removal rate was 96.22%. Furthermore, it was found that hydroxyl radicals produced by hydrogen peroxide initiated the bond breaking and ring-opening reactions in organic matter, which eventually degraded organic matter into water and carbon dioxide.

The current study reports a multi-functional superabsorbent resin (SAR) developed from blending waste plastics. The new process successfully overcame the incompatibility of blending waste plastics through polymerization process and the products could be used as water-retaining agent and desiccant. Structure studies indicated that the monomer was successfully grafted onto the blending waste plastics, causing improved thermal stability and a porous and coarse surface. The maximum water absorbing capacities reached 343 and 125 g/g in distilled water and tap water, respectively, and the optimum operation temperature, reaction time, mass ratio of waste plastics to monomer, the amounts of cross-linker and initiator were respectively 95 °C, 3 h, 1:8, 0.25 wt% and 0.60 wt%, The swelling kinetic mechanism of the prepared SAR was well described by pseudo-second order and non-Fickian diffusion type followed an anomalous mechanism. Moreover, the product could be applied in a vast pH range of 3–10, and also could be cyclic utilization. In addition, the SAR showed superior moisture absorbing capacity which was 3–5 times higher than that of commercial desiccants under the same condition. Accordingly, this study provides a practical, environmentally friendly and high value-added approach for blending waste plastics recycling.

Spaceflight solid waste (SSW) is different from terrestrial municipal solid waste since it contains quite amount of medicines needing co-disposal sometimes. Harmless co-disposal of the hazardous drug discarded into SSW is extremely important for safe operation of the Environmental Control and Life Support System (ECLSS) during long-term space missions. In this work, hydrothermal oxidation (HTO) process was proposed for detoxification and mineralization treatment of the blend waste comprising of SSW and waste drugs (diclofenac sodium, DS). The results showed that a large number of toxic chlorinated organics were detected in the hydrothermal process without oxidant. On the contrary, in the presence of oxidant (H2O2), an efficient dechlorination and detoxification level was achieved above 300 °C. The optimal conditions including temperature, time and H2O2/waste (H/S) ratio were 300 °C, 30 min and 30 mL/g, respectively. The dechloridation efficiency and carbon conversion efficiency under the optimal conditions were over 95% and 77%, respectively. Furthermore, a suitable concentration of nitrate, TOC and COD were also obtained under the optimal conditions, implying that the by-products after the HTO process exhibited the potential for plant growing in the ECLSS. Compared with other oxidation techniques for waste disposal in space, HTO process exhibited significant technical advantages of disposing the blend waste containing waste medicines and SSW. Accordingly, HTO process was recommended as a promising, efficient and environment-friendly method to dispose spaceflight solid waste containing various types of hazardous matters during long-term space missions.

Recovery of high-content and valuable elements including phosphorus (P) is critical for recycling of spent LiFePO

Recycling of solid waste for oxygen recovery in manned spacecraft is extremely important during long-term space missions. In the current study, pyrolysis process was evaluated to investigate the recovery potential of oxygen from spaceflight solid waste (SSW). A low fidelity waste surrogate (LFWS) was employed to simulate the solid waste produced during long-term space missions, and the oxygen distribution and oxygen-containing species in various pyrolysis products were investigated. In comparison with terrestrial municipal solid waste, SSW has higher content of oxygen, nitrogen and sulfur, but the content of carbon is much lower. The amount of oxygen recovered from SSW was higher than from terrestrial solid waste by pyrolysis treatment. Moreover, much more oxygen in SSW could be easily converted into the gaseous phase for oxygen recovery by adjusting treatment temperature. Nearly 50% of oxygen in SSW was recovered in the form of the gaseous product, and the optimal oxygen recovery efficiency was 29.54% at 700 °C. Recycling oxygen from SSW is a desirable approach to improve the closure level of oxygen cycle in the life support system. This work provides fundamental information for oxygen recycling from SSW during long-term space missions.

Dry cleaning of waste plastic is urgently required to substitute traditional wet cleaning, especially in arid areas. Nevertheless, it is still limited by relatively poor cleaning performance. This study reports a novel, effective and sustainable dry cleaning system for waste plastic purification in gas-solid media. An agitated fluidized bed and Geldart B silica sand were employed to fulfill the dry cleaning process without any consumption of water. With gravimetric and spectroscopic methods determining cleaning performance index, superficial gas velocity, bed height, temperature, agitation speed and cleaning time were investigated to evaluate their influence on dry cleaning performance. Under the moderate operating conditions, the gravimetric and spectroscopic indexes of the dry cleaning reached up to 98.4% and 95.0%, which were close to those of routine caustic washing (99.2% and 98.9%). Furthermore, the dry cleaning turned in a similar performance by visual inspection, as well as a similar surface transition of more hydrophilicity compared with caustic washing. Mechanism analysis indicated that mutual interaction between fluidization and agitation facilitated adhesion breaking and dispersing of contaminants into gas-solid media due to sufficient collisions and mass transfer. Triboelectrification that resulted in redeposition of fine powder should be avoided to further improve dry cleaning performance. This study provides theoretical and practical guidance for dry cleaning of contaminated waste plastics.

Amphoteric superabsorbent resin (SAR) is excellent in both cation and anion adsorption. In the present study, typical waste polyethylene film was employed to develop a novel amphoteric SAR through polymerization with acrylic acid (AA) and dimethyl diallyl ammonium chloride (DMDAAC). The maximum water absorbing capacities of the obtained amphoteric SARs for distilled water and rainwater reached 286.3 and 213.5 g/g, respectively. A determination of the structure and morphology of the amphoteric SAR confirmed that monomers were successfully grafted onto the plastic film. The water absorbing capacity of SAR was greatly affected by the monomer to waste polyethylene ratio, the amount of initiator and cross-linker, the neutralization degree of acrylic acid and external solution. Meanwhile, the swelling kinetic, pH sensitivity, water retention and reswelling ability of the prepared polymer were also systematically investigated. This study provides a novel process for value-added recycling of waste polyethylene film.

Comprehensive utilization of phosphorus from spent LiFePO4 (LFP) battery has aroused considerable interest aiming to enhance the economic profit of recycling this type of low value-added battery. In the current study, a green and novel process was developed to recover phosphorus from spent LFP battery, which was further directly converted into phosphorus grafted slow-release fertilizer (P-SRF) with acid-resistance. Meanwhile, Li was simultaneously recovered. Effect of several parameters on the leaching efficiency of P was investigated, and the properties of P-SRF in acid and neutral conditions were clarified. In the whole process, the recovery efficiencies of Li and P were more than 99.5%, and furthermore, the synthesized P-SRF had high water-absorbing capacity and low release rate in both acid and neutral conditions. Mechanism study indicated phosphorus was recovered in the form of HPO42−/H2PO4− from spent LFP battery. HPO42−/H2PO4− reduced the activation energy of the condensation reaction between urea and acrylic acid to accelerate the reaction. Meanwhile, the low release rate of P-SRF in low pH was ascribed to the buffering effects of HPO42−/H2PO4−. Furthermore, pot experiments showed P-SRF effectively promoted the growth of maize. This study provided a profitable approach for high value-added recovery of spent LFP battery, and the recovered hydrophosphate could be further transferred into P-SRF with considerable acid-resistance, which has potential application in acid soil, horticulture and slope treatment.

A comprehensive sound absorption material was developed using waste agricultural plastic film as raw material. Comparing to traditional acoustic materials such as porous materials and perforated plates, the new material exhibited excellent sound absorption capability in both low- and high-frequency ranges and had a complex structure with perforations, cavities, and an air layer. The optimal average sound absorption coefficients of the material were 0.44 and 0.53 within the frequency ranges of 200–1600 and 500–6400 Hz, respectively. Furthermore, the low-frequency absorption range of the material could be adjusted according to the actual noise absorption requirements, thus broadening its application ranges. The density of the material is 0.55 g/cm 3 while its thickness is only 1 cm. Thus, it is lighter than most conventional sound absorption materials. The compressive strength of the samples were 0.56 ± 0.01 MPa (unmanufactured), 0.51 ± 0.01 MPa (4 perforations) and 0.45 ± 0.02 MPa (4 perforations and 12 cavities) respectively and, its flexural strength was 91.2 ± 1.22 N. Interfering tests indicated that water coverage could decline the sound absorption efficiency in all frequency ranges, while sand coverage only declined the low frequency absorption, but increased the high frequency absorption effect of the material. Accordingly, it is believed that the new waste-derived material is quite suitable for application on bridges and inside tunnels during high-speed road construction, and also appropriate for using as parts of vehicles and ceilings etc.

The disposal of waste polyvinyl chloride plastics (PVC) has become a major challenge due to the generation of chlorinated pollutants. In the current study, a new process was developed to produce a novel growth substrate with waste PVC and superabsorbent resin (SAR) as raw materials. The main merits were that no hazardous chlorinated by-products were formed under low reaction temperature and a chemical bridge was constructed between SAR and waste PVC via free radical reaction which effectively prevented the loss of SAR and guaranteed sustainable water supply. Structure and morphology studies confirmed that SAR was firstly modified by various silane coupling agents, then incorporated into waste PVC to prepare the substrate by compression-molding foaming process. The maximum water absorbing ratio of the product reached 623% with only 1.65% mass loss under optimum conditions. Moreover, the tensile strength, elongation at break and compression strength of the substrate increased by 84.37%, 52.53%, and 6.47% than the untreated case, respectively. Furthermore, the swelling behavior, reusability and plant cultivation capacity of the new product were also studied systematically. This study provides an efficient process to recycle waste PVC for a sustainable and cost-effective growth substrate preparation.

In the present study, cathode materials (C/LiCoO2) of spent lithium-ion batteries (LIBs) and waste polyvinyl chloride (PVC) were co-processed via an innovative mechanochemical method, i.e. LiCoO2/PVC/Fe was co-grinded followed by water-leaching. This procedure generated recoverable LiCl from Li by the dechlorination of PVC and also generated magnetic CoFe4O6 from Co. The effects of different additives (e.g. alkali metals, non-metal oxides, and zero-valent metals) on (i) the conversion rates of Li and Co and (ii) the dechlorination rate of PVC were investigated, and the reaction mechanisms were explored. It was found that the chlorine atoms in PVC were mechanochemically transformed into chloride ions that bound to the Li in LiCoO2 to form LiCl. This resulted in reorganization of the Co and Fe crystals to form the magnetic material CoFe4O6. This study provides a more environmentally-friendly, economical, and straightforward approach for the recycling of spent LIBs and waste PVC compared to traditional processes.

In this study, supercritical methanol (SCM) process was successfully used for the preparation of ultrafine copper materials from waste printed circuit boards (PCBs) after nitric acid pretreatment. Waste PCBs were pretreated twice in nitric acid. Sn and Pb were recovered by the first nitric acid pretreatment. The leach liquor with a high concentration of copper ions after the second nitric acid leaching was subjected to SCM process. The mixture of Cu and Cu 2 O with poor uniformity of particle size was formed due to the effect of ferric iron contained in the leach liquor of waste PCBs, while more uniform and spherical Cu particles with high monodispersity and smaller size could be prepared after the removal of Fe. The size of Cu particles increased obviously with the decline of SCM temperature, and particles became highly aggregated when the reaction temperature decreased to 300 °C. The size of Cu particles decreased markedly with the decrease of initial concentration of copper ion in the leach liquor of waste PCBs. It is believed that the process developed in this study is simple and practical for the preparation of ultrafine copper materials from waste PCBs with the aim of recycling these waste resources as a high value-added product.

Impurity Fe could severely damage the performance of resynthesized cathode material, and therefore, LiFePO

Electronic display housing plastics contain a high amount of halogenated compounds such as brominated flame retardants (BFRs) and polyvinyl chloride (PVC). Compared with moderate critical conditions of conventional eco-friendly sub/supercritical carbon dioxide (Sc-CO

In this study, a novel reutilization method for waste printed circuit boards (PCBs) as flame retardant and smoke suppressant for poly (vinyl chloride) (PVC) was successfully testified. A supercritical water oxidation (SCWO) process was applied to treat waste PCBs before they could be used as flame retardants of PVC. The results indicated that SCWO conditions had a significant effect on the flame retarding and smoke suppressing properties of waste PCBs for PVC. Cu 2 O, CuO, and SnO 2 were the main active ingredients in waste PCBs-derived flame retardants. A conversion of Cu elements (Cu 0 → Cu + → Cu 2+ ) during SCWO process with the increase of reaction temperature was found to be the key influence factor for the flame retarding properties of SCWO-treated PCBs. The experiment results also showed that there was a synergistic effect of flame retardancy between Cu + and Cu 2+ . After the optimized SCWO treatment, SCWO-treated PCBs significantly improved the flame retardancy and smoke suppression of PVC. Limiting oxygen index (LOI) and char yield (CY) increased with increasing SCWO-treated PCBs content in PVC, while smoke density rating (SDR) and maximum smoke density (MSD) decreased markedly. The mechanical properties of PVC samples were influenced in different degree by adding different content SCWO-treated PCBs.

In the current study, an environmental benign process namely mechanochemical approach was developed for cobalt and lithium recovery from spent lithium-ion batteries (LIBs). The main merit of the process was that neither corrosive acid nor strong oxidant was applied. In the proposed process, lithium cobalt oxide (obtained from spent LIBs) was firstly co-grinded with various additives in a hermetic ball milling system, then Co and Li could be easily recovered by a water leaching procedure. It was found that EDTA was the most suitable co-grinding reagent, and 98% of Co and 99% of Li were respectively recovered under optimum conditions: LiCoO2 to EDTA mass ratio 1:4, milling time 4h, rotary speed 600r/min and ball-to-powder mass ratio 80:1, respectively. Mechanisms study implied that lone pair electrons provided by two nitrogen atoms and four hydroxyl oxygen atoms of EDTA could enter the empty orbit of Co and Li by solid-solid reaction, thus forming stable and water-soluble metal chelates Li-EDTA and Co-EDTA. Moreover, the separation of Co and Li could be achieved through a chemical precipitation approach. This study provides a high efficiency and environmentally friendly process for Co and Li recovery from spent LIBs.

Recovery of high-content and valuable elements including phosphorus (P) is critical for recycling of spent LiFePO4 battery, but P recovery is challengeable due to the poor solubility of lithium phosphate and iron phosphate. This study compared two strategies to recover P by adopting sulfide salt to induce P dissolution, i.e., recovery of P directly from LiFePO4, and step-by-step recovery of Li then P. The results revealed that the second strategy was more efficient because of the higher recovering efficiency and selectivity. Accordingly, an acid-free process to recover P was successfully demonstrated. Li-recovery efficiency of 97.5 % was reached at a leaching time of 65 min, and nearly 100 % P-recovery efficiency was reached at 5 h. Mechanism analysis revealed that the transforming of delithiated LiFePO4 crystal to NaFeS2 was mainly responsible for P dissolution. Thermodynamic analysis and density functional theory calculation further proved the transformation reaction, and a stepwise-transformation mechanism was proposed. In addition, P was reclaimed in the form of soluble phosphate salts. The process is especially appealing due to its environmental and economic benefits for recycling spent LiFePO4 batteries.

Impurity Fe could severely damage the performance of resynthesized cathode material, and therefore, LiFePO4 cathode should be removed from the mixed spent LIBs for materials recycling. In this research, a non-hydrometallurgy method has been developed to separate LiFePO4 by selectively peeling-off the LiFePO4 cathode material and the peeling-off process was well explained by theoretical modeling. The peeling-off efficiency of LiFePO4 was approximate 100 % and that of LiMn2O4/LiCoO2/Li(Ni, Co, Al)O2/Li(Ni, Mn, Co)O2 was only 0.08 %. That is, the separating selectivity was 1250. Mechanism study revealed that the peeling-off was achieved through selective destruction of the LiFePO4 crystal and the matrix of polyvinylidene fluoride (PVDF) binder. Particularly, the crystal structure of LiFePO4 was firstly destructed by sulfide, thus LiFePO4 particles were detached from the matrix of PVDF binder. Then, the PVDF binder without LiFePO4 particles filling were more susceptible to be brittlely peeled off by the micro-explosion force of hydrogen from the reaction of Al foil with water due to the weakened mechanical strength. The process is suitable for recycling varied types of spent LIBs, having a strong potential for industrial application.

Steam is widely used to enhance heavy oil recovery, whereas it is implemented as just an auxiliary thermal source when treating oily sludge. In this study, steam jet was for the first time introduced to simultaneously reclaim and purify oil from layered oily sludge, a hazardous waste in storage ponds of oil joint stations. The effect of steam jet on oil reclamation and purification was investigated with various operating temperatures (200–350 °C) and mass ratios of steam to oily sludge (2:1–8:1). Batch experiments indicated that a high steam jet performance was achieved at 300 °C and 6:1 of the mass ratio, with 92% of oil reclamation rate and 82% of demetallization rate from the oily sludge of upper layer within 5 min. The mild temperature of the injection area (97 °C) was in favor of retaining light fractions of oil. Besides, the dynamic process of this steam-based treatment was numerically simulated with COMSOL to illuminate interactions among steam, oil and condensed water. With a significant reduction of oil viscosity due to steam heating, high dynamic pressure of steam jet was found to disturb the surface of layered oily sludge, expediting oil flotation in water. Meanwhile, the intense steam jet could also sufficiently scatter the floated oil to diffuse metallic impurities from oil droplets into surrounding water. The reclaimed oil after steam injection was more upgradable for a refinery while the residual oily sludge became more treatable with traditional recycling.

Electronic display housing plastics contain a high amount of halogenated compounds such as brominated flame retardants (BFRs) and polyvinyl chloride (PVC). Compared with moderate critical conditions of conventional eco-friendly sub/supercritical carbon dioxide (Sc−CO2), a novel and sustainable procedure by using improved Sc−CO2 was developed for disposal of this type of plastic. The main merit of the process was that complex halogen-containing plastics were safely disposed and halogen-free products were recycled without using catalysts or additives. It was discovered that additive BFRs were initially extracted by Sc−CO2 technique and then it decomposed accompanied with PVC rapidly to form HBr and HCl, which could be separated by traditional bromine stripping techniques from seawater. Based on response surface methodology (RSM), the maximum debromination and dechlorination efficiencies were achieved at 99.51% and 99.12% respectively. After the treatment, halogen-free products such as solid carbon materials and organic chemical feedstocks were obtained. Mechanism study elucidated that free radicals reaction involving chain initiation, growth and termination induced the polymer decomposition to form these products. This study provides an applicable and green approach for disposal and recovery of halogen-containing plastics.

In the current study, the possibility of incorporating various industrial wastes into fireproofing materials was investigated. It was found that the newly developed materials showed excellent air sealing and fireproofing performance, with air permeability coefficients 3 to 4 orders of magnitude smaller than traditional fire prevention materials. The influence of different parameters on the air permeability was investigated, and the air sealing mechanisms were clarified through microstructure analysis. In addition, the workability and mechanical properties of the fireproofing materials for practical application in coal mine were studied. The new materials derived from industrial wastes had a compact and monolithic structure, and the excellent air tightness could be attributed to the pozzolanic activity of the industrial wastes and the film-forming property of organic polymers. Among the industrial wastes examined, a special coal fly ash with high pozzolanic activity and little free calcium oxide derived the best product with air permeability coefficient, tensile strength and breaking elongation of 4.17 × 10-8 m2/s, 2.14 MPa and 48.90%, respectively. This study provides an economical, environmentally friendly and promising approach for industrial wastes recycling.

Precious metals are the most attractive resources in waste printed circuit boards (PCBs) of mobile phones. In this work, an alternative process for recovering Au, Ag, and Pd from waste PCBs of mobile phones by supercritical water oxidation (SCWO) pre-treatment combined with iodine-iodide leaching process was developed. In the process, the waste PCBs of mobile phones were pre-treated in supercritical water, then a diluted hydrochloric acid leaching (HL) process was used to recovery the Cu, whose leaching efficiency was approximately 100%, finally the resulting residue was subjected to the iodine-iodide leaching process for recovering the Au, Ag, and Pd. Experimental results indicated that SCWO pre-treatment temperature, time, and pressure had significant influence on the Au, Ag, and Pd leaching from (SCWO+HL)-treated waste PCBs. The optimal SCWO pre-treatment conditions were 420°C and 60min for Au and Pd, and 410°C and 30min for Ag. The optimum dissolution parameters for Au, Pd, and Ag in (SCWO+HL)-treated PCBs with iodine-iodide system were leaching time of 120min (90min for Ag), iodine/iodide mole ratio of 1:5 (1:6 for Ag), solid-to-liquid ratio (S/L) of 1:10g/mL (1:8g/mL for Ag), and pH of 9, respectively. It is believed that the process developed in this study is environment friendly for the recovery of Au, Ag, and Pd from waste PCBs of mobile phones by SCWO pre-treatment combined with iodine-iodide leaching process.

This work reports a special bio-fuel derived from sludge. Heat value, density, dropping intensity and heating stability were examined, and the influences of various process parameters were established. It was found that the addition of an aiding agent could increase the caloric value and higher briquetting pressure contributed to the quality and stability of the bio-fuel. Furthermore, the combustion properties of the bio-fuel products under different temperature were investigated.

Raw biomass washing prior to pyrolysis treatment has been employed to mitigate the ash-related problems encountered during resultant biochar combustion. However, wide-spread application of this approach is limited by high energy consumption and low washing efficiency. In the present study, the biochar washing instead of raw biomass washing was attempted to overcome aforementioned problems, and fuel qualities of washed biochars were investigated for the first time. The results showed that major ash forming metals can be efficiently removed by all tested washing agents (de-ionized water (DW), acetic acid (AA) and citric acid (CA)), especially for acid washing agents AA and CA. As a consequence, the ash content of the biochars decreased, and the slagging and fouling issues were dramatically mitigated. Due to metal removal, the washed biochars exhibited improved combustion properties, especially for the biochars derived from agricultural biomass. In addition, noticeable decreases in nitrogen and sulfur contents were observed following washing treatment, suggesting the additional benefit of reducing emissions of nitrogen and sulfur pollutants during washed biochar combustion. Compared to raw biomass washing prior to pyrolysis, the significantly increased washing efficiency and fuel quality and decreased hydrophilicity of the biochars indicate that pyrolysis combined with subsequent biochar washing is more suitable to produce solid fuel biochars with high fuel quality from different source of waste biomass. (C) 2015 Elsevier B.V. All rights reserved.

In this study, pure TiO2-nanoparticles and TiO2/sewage sludge (TS) as biomass material were synthesised via a sol–gel method. The adsorption potential of nanosized TiO2 and TS for removal of Cd(II) was investigated in a batch system. The prepared adsorbents were characterised using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The XRD analysis showed that pure TiO2 is in amorphous phase before calcination and in anatase phase at annealing temperature of 400 °C. TiO2/sewage sludge that calcined at 400 °C (TS400) was found to be the best adsorbent for cadmium removal from aqueous solution. Kinetic and isotherm studies were carried out by considering the parameters, pH, initial concentration and contact time. The optimum pH value for Cd(II) adsorption onto TS400 was found to be 6. Langmuir isotherm showed better fit than Freundlich isotherm and the maximum adsorption capacity was found to be 29.28 mg/g which is higher than that of many oth...

The present study reports a mechanochemical (MC) process for effective recovery of copper (Cu) and precious metals (i.e. Pd and Ag) from e-waste scraps. Results indicated that the mixture of K2S2O8 and NaCl (abbreviated as K2S2O8/NaCl hereafter) was the most effective co-milling reagents in terms of high recovery rate. After co-milling with K2S2O8/NaCl, soluble metallic compounds were produced and consequently benefit the subsequent leaching process. 99.9% of Cu and 95.5% of Pd in the e-waste particles could be recovered in 0.5mol/L diluted HCl in 15min. Ag was concentrated in the leaching residue as AgCl and then recovered in 1mol/L NH3 solution. XRD and XPS analysis indicated that elemental metals in the raw materials were transformed into their corresponding oxidation state during ball milling process at low temperature, implying that solid-solid phase reactions is the reaction mechanism. Based on the results and thermodynamic parameters of the probable reactions, possible reaction pathways during ball milling were proposed. Suggestion on category of e-waste for ball milling process was put forward according to the experiment results. The designed metal recovery process of this study has the advantages of highly recovery rate and quick leaching speed. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste.

An environmental benign, non-acid process was successfully developed for selective recovery of palladium from waste printed circuit boards (PCBs). In the process, palladium was firstly enriched during copper recovery procedure and dissolved in a special solution made of CuSO4 and NaCl. The dissolved palladium was then extracted by diisoamyl sulfide (S201). It was found that 99.4% of Pd(II) could be extracted from the solution under the optimum conditions (10% S201, A/O ratio 5 and 2 min extraction). In the whole extraction process, the influence of base metals was negligible due to the relatively weak nucleophilic substitution of S201 with base metal irons and the strong steric hindrance of S201 molecular. Around 99.5% of the extracted Pd(II) could be stripped from S201/dodecane with 0.1 mol/L NH3 after a two-stage stripping at A/O ratio of 1. The total recovery percentage of palladium was 96.9% during the dissolution-extraction-stripping process. Therefore, this study established a benign and effective process for selective recovery of palladium from waste printed circuit boards. (C) 2014 Elsevier B.V. All rights reserved.

This work reports the detoxification effect of chlorinating volatilization procedure on waste lead glass. The effects of various reaction parameters on lead removal efficiencies were examined, and the optimal operation conditions were 1000 °C, 2 h, and 600 ± 50 Pa, respectively. Moreover, it was found that the residues could be safely applied in a wide range, e.g., for wollastonite synthesis by an environmental benign technique. Accordingly, the typical hazardous waste was successfully converted into a safe raw material for further industrial application.

The current study was carried out to develop a novel process, namely chloride volatilization procedure for lead recovery from waste cathode ray tube (CRT) funnel glass. In the recovery system, the glass powder was first compressed into cylindrical pellet homogeneously with chlorinating agents, and then subjected to thermal treatment for solid-phase reaction. In this case, lead could be easily released from the silicon oxide network of the glass and it was recovered in the form of PbCl₂. It was found that CaCl2 was the most effective chlorinating agent, and the optimum operation temperature, holding time and system pressure were 1000 °C, 2 h, 600 ± 50 Pa, respectively. The evaporated PbCl₂could be easily recovered by a cooling device. The evaporation ratio of lead from waste CRT was 99.1% and the purity of the recovered PbCl₂product was 97.0%. The reaction routes and lead recovery mechanisms of the process were identified. This study provides an efficient and practical process for waste CRT funnel glass detoxification and recycling.

Organophosphorus flame retardants (PFRs) have been largely used in waste printed circuit boards (PCBs) because of the regulation of brominated flame retardants (BFRs) in recent years. In the present study, triphenyl phosphate (TPPO), a typical PFR, contained in waste PCBs was tentatively subjected to solvothermal treatment in order for efficient recycling of this type of valuable resource. Experimental results showed that the optimum operation temperature, time and liquid to solid ratio for TPPO removal were 90 °C, 120 min and 10:1, respectively. After solvothermal treatment, TPPO was transferred into the solvents and solid TPPO powder was easily recovered through vacuum rotary evaporation. The TPPO recovery efficiency reached 84.4% in a purity of 93.4% and dephosphorization efficiency of waste PCBs reached 97.3%. Shrinking core model (SCM) indicated that both interface transfer and internal diffusion affected the recovery rate of TPPO in the solvothermal process. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) profiles of the recycled TPPO were in good agreement with TPPO standard material indicating that the structure of the recycled TPPO maintained after the recovery process. This work provides a clean and applicable process for PFRs recovery from waste PCBs.

In this work, an effective process for removal of brominated flame retardants (BFRs) and recovery of Cu and Pb from waste printed circuit boards (PCBs) was developed. In the process, waste PCBs and polyvinyl chloride (PVC) were co-treated by subcritical water oxidation (SBWO). PVC was used as a hydrochloric acid source and waste PCBs was used as a neutralizing reagent for the produced HCI. The dechlorination of PVC, removal of BFRs, and recovery of Cu and Pb could be achieved simultaneously by the one-step SBWO reaction. Experimental results showed that the dechlorination of PVC was complete when SBWO temperature exceeded 250 degrees C. SBWO co-treatment was high efficient for the leaching of Cu and Pb from waste PCBs, and XRD spectra indicated that Sn was immobilized as SnO2 in the residue after co-treatment. The optimum SBWO co-treatment conditions were temperature of 350 degrees C, time of 60 min, solid-liquid ratio of 1:9 g/ml, and PVC-to-PCBs ratio of 1:1, respectively. In the optimized co-treatment, 98.9% of Cu and 80% of Pb were recovered, while the leaching efficiencies of Sn and Cr were 15.3% and 3.9%, respectively. Meanwhile, approximately 100% of the bromine was changed Into HBr and enriched in water after co-treatment. (C) 2013 Elsevier B.V. All rights reserved.

In the present study, a green process for cuprous chloride synthesis from waste printed circuit boards (PCBs) was developed. High value-added cuprous chloride (98.7% purity) was obtained by treating metallic particles of waste PCBs with solution of cupric sulfate and sodium chloride. Typical noble metal (Pd) was dissolved by forming a stable chloride complex during the synthesis process as Cu2+ played the role of oxidant or concentrated in the residue. Under the optimum condition (VNaCl/mCuSO4 ratio = 6, [C/[Cu2+] mole ratio = 1.05, treatment time = 30 min, operation temperature = 60 °C), yield of cuprous chloride was 74.0% and approximately 98.5% of the copper could be recovered. It is believed that the process proposed is effective and practical for Cu recovery from waste PCBs.

E-waste contains high amount of brominated flame retardants (BFRs) which are toxic, bioaccumulative and recalcitrant. In the present study, an effective and environmental-friendly process using solvothermal treatment to extract tetrabromobisphenol A (TBBPA), a typical BFR from waste computer housing plastic was developed. After the solvothermal process, TBBPA were transferred into a special solvent phase and the bromine content in plastic after solvothermal treatment was greatly reduced, which confirmed the feasibility of solvothermal procedure for TBBPA extraction. This work provides a clean and applicable process for extraction of BFRs from plastic in e-waste.

Construction and demolition waste (C&D) was employed as a raw material to synthesize sorbent by fusion-hydrothermal process in order to effectively use this type of waste material. The specific surface area and the cation exchange capacity (CEC) values of the sorbent were 308.2 m2 g-1 and 625.6 mmol/100 g-1, respectively. It was found that the sorbent was quite effective for ammonium ion due to the high CEC value. The sorbent possessed high PFOS sorption capacities after load with cationic surfactant (Cetyltrimethyl Ammonium Bromide, CTAB), the sorption capacities of CTAB-modified sorbents enhanced with the increase of CTAB loading amount. This study provides an effective way for the C&D waste utilization.

The disposal of construction and demolition (CD) waste has become a serious problem in China due to the rapid increase of Chinese construction industry in recent years. In the present study, typical CD waste was employed for ceramsite fabrication so as to find a new way for its effective recycling. A novel process was developed for manufacturing high-quality porous ceramsite according to the special chemical composition and properties of CD waste. Most importantly, a unique bloating agent was developed for the porous structure formation since it was difficult to obtain a suitable porous structure using traditional bloating agents. The effects of processing parameters such as sintering temperature, heating rate and soaking time were investigated, and the bloating mechanism for ceramsite was discussed. The CD waste ceramsite (CDWC), with high-intensity, low density and homogeneous mechanical properties, was much more suitable for application in the construction field. This study provides a practical process for efficient recycling of the rapidly increasing quantities of CD waste.