Response to the Upcoming Emerging Waste: Necessity and Feasibility Analysis of Photovoltaic Waste Recovery in China.

With the widespread photovoltaic deployment to achieve the net-zero energy goal, the resulting photovoltaic waste draws attention. In China, considerable steps have not been taken for photovoltaic waste management. The lack of relevant scientific information on photovoltaic waste brings difficulties to the establishment of photovoltaic waste regulatory systems. In this study, the necessity and feasibility of photovoltaic waste recovery were investigated. In China, the photovoltaic waste stream was quantified as 48.67-60.78 million t in 2050. In photovoltaic waste, indium, selenium, cadmium, and gallium were in high risk, judging by the metal criticality analysis, which meant that their recovery was significant to alleviate the resource shortage. The full recovery method was proved to reduce the environmental burdens most. For cost and benefit analysis, the net present value/size was -1.02 $/kg according to the current industrial status. However, it can be profitable with the recovery of silver. This study provides scientific and comprehensive information for photovoltaic waste management in China and is expected to promote the sustainable development of photovoltaic industry.

Visualizing and assessing the size-dependent oral uptake, tissue distribution, and detrimental effect of polystyrene microplastics in Eisenia fetida.

Microplastics are widely distributed in the environment, their potential ecological risks on soil organism have attracted extensive attention, while the investigation of the size effect on its accumulation and toxicity in soil invertebrates are still lacking. In this study, we set out to explore the size-dependent effects of microplastics on soil invertebrates with different doses. Specifically, we investigated the effect of polystyrene (PS) microplastics on earthworm Eisenia fetida with three different sizes (70 nm, 1 µm and 10 µm) and exposure doses (0.5%, 5% and 10% w/w in food). Results showed that PS microplastics had no effects on the mortality of E. fetida, while an obvious growth inhibition with rising exposure concentrations was observed, especially under exposure of 70 nm plastic particles. Additionally, 70 nm PS microplastics induced more serious oxidative stress, energy depletion and histopathological damage on earthworms compared with larger sizes. The accumulation and distribution pattern of microplastics was size-dependent in earthworms after 3- and 7-day exposure as revealed by laser confocal microscopy. Notably, earthworms accumulated more micro-sized particles (MPs, 10 µm and 1 µm) but with less toxic responses, suggesting its weaker toxicity. The distribution pattern of MPs may explain the weak relation between accumulation and toxicity as they mainly distributed in epidermis of mid- and tail-section and the intestine of earthworm. In contrast, nano-sized particles (NPs, 70 nm) were more distributed in the head-section and subcutaneous tissue of the skin, which was in accordance with the obvious toxic responses found in earthworms exposing to NPs. Our study highlighted the importance of size in determining the accumulation, distribution and toxic effects of plastic particles towards soil invertebrates and advocates the necessity of ecological risk assessments of NPs.

An energy-saving and environment-friendly technology for debromination of plastic waste: Novel models of heat transfer and movement behavior of bromine.

The recovery and reuse of waste brominated resin, which is a typical plastic waste, is troublesome because it contains toxic brominated flame retardants. Conventional pyrolysis of brominated resin was suggested to be an effective approach for debromination. However, conventional pyrolysis caused high energy consumption and high yield of toxic volatiles. An energy-saving and environment-friendly technology called infrared heating was reported in this study. According to computation of the developed heat transfer models, the critical debromination temperature was 260 °C in infrared heating, which was 271 °C lower than conventional pyrolysis. Meanwhile, no volatile product appeared in the reported technology. In the pyrolysis residue after infrared heating, bromine concentrated orientationally in the fixed and limited area on the resin particles. Free radicals, such as •CH3, H•, and Br•, were combined with Br• generated in infrared heating to form the concentrated bromine. Compared to the chaotic distribution of bromine in conventional pyrolysis, the orientational concentration of bromine was a progress for removing and collecting bromine in infrared heating. Moreover, compared to conventional pyrolysis, infrared heating could decrease 76.2% energy consumption. This work contributed to provide the novel technology for recovery of plastic wastes.

Assessment of precious metals positioning in waste printed circuit boards and the economic benefits of recycling.

In this study, the distribution of precious metals in waste printed circuit boards was investigated and the economic value of recycling was assessed. Contacts of pins, slots, interfaces and the board surface in waste printed circuit boards were analyzed, and three types of precious metals were detected. The content of gold, silver and palladium ranged from 179.86 mg/kg to 3694.51 mg/kg, 809 mg/kg to 12320.51 mg/kg and 96.25 mg/kg to 117.49 mg/kg, respectively. Gold was distributed wildly in contacts of many slots and all interfaces, while contacts of only two interfaces (the cable and USB) contained palladium. The highest content of Au was found in contacts of the cable. Silver mainly concentrated on pins (metal foil contacts) of electronic components and its highest content was found in microchips. The economic value of recyclable precious metals in 1 t waste printed circuit boards was up to 2292.94 dollars, of which Au contributed 98%. This study indicates the prominent economic benefits of precious metal recovery from waste printed circuit boards. Moreover, the scientific information provide guidance for the directional and accurate recovery of precious metals from waste printed circuit boards.

Analysis of contaminants and their formation mechanism in the desiccation-dissociation process of organic impurity of waste glass.

The recovery of waste glass is an important issue in the fields of social sustainable development and resource recovery. The removal of organic impurity is the first step in the recovery of waste glass. Currently, desiccation-dissociation technology is advised to remove the organic impurity from waste glass. However, the risks of the organic impurity desiccation-dissociation process of waste glass have not been reported in the literature. In this paper, the environmental risks of the organic impurity desiccation-dissociation process of waste glass were assessed. The assessment results indicated that none of TSP (0.143 mg/m3), PM10 (0.090 mg/m3), heavy metals in air and residue after desiccation-dissociation were contaminated. However, the gas contained abundant organic contaminants, especially benzene, whose content was up to 5.26%. Molecular dynamics simulation and contaminant formation pathways analysis indicated that the formation of gaseous organic contaminants was because overmuch small molecular free radicals were generated at 200 °C and combined with each other. Hence, reducing the temperature of desiccation-dissociation, wearing gas masks, and placing organic gas contaminant absorption liquids are necessary protective measures. This paper provides scientific data for the green development of organic impurity desiccation-dissociation technology of waste glass. Meanwhile, this paper makes up for the shortage of the environmental information of the organic impurity desiccation-dissociation of waste glass.

In Situ Recombination of Elements in Spent Lithium-Ion Batteries to Recover High-Value γ-LiAlO2 and LiAl5O8.

Recovering valuable materials from spent lithium-ion batteries is an important task because of the asymmetry in resource distribution, supply, and demand around the world. A lithium-ion battery is a combination system of various elements and their oxides. Current recovering technologies focus on the separation of valuable metal elements. They can inescapably bring secondary contamination and cost to the environment due to the addition of leachants and precipitants. To recover valuable materials, in situ recombination of elements in spent lithium-ion batteries can be a more economical and environment-friendly solution. Herein, we developed a technology based on in situ aluminothermic reduction and interstitial solid solution transformation to recover high-value γ-LiAlO2 and LiAl5O8 under vacuum and high-temperature (1723 K) conditions. It was found that the process of Li2O filling into the lattice of O-Al-O structure is an energy-reducing process, while LiAl5O8 was an existing high-energy transition-state matter. Since there was no wastewater generated, the process brought a new environment-friendly method for recovering valuable metals from spent lithium-ion batteries. This study also provides new comprehension regarding the design for high-value products' recovery from multi-element mixed wastes on an atomic scale.

Do essential elements (P and Fe) have mitigation roles in the toxicity of individual and binary mixture of yttrium and cerium to Triticum aestivum?

Essential elements can affect the bioavailability, uptake, and toxicity of metals. However, hardly any research has focused on the roles of essential elements on the toxicity of rare earth metals. Here we examined how P and Fe modified the individual and binary toxicity of Y and Ce to Triticum aestivum, respectively. Standard root elongation tests were used to quantify the toxicity of both single and binary mixtures at three levels of P addition (1, 5, and 10 µM) and Fe addition (0.1, 1, and 5 mM). Our results showed that both P and Fe can alleviate individual toxicity of Y or Ce irrespective of the dose indicators as suggested by the enhanced EC50 values. Both P and Fe might mitigate Y/Ce toxicity by limiting Y/Ce uptake into roots and improving nutritional status of wheats, whereas P can also decrease free Y/Ce ion activities in the exposure media. As for the mixture toxicity of Y and Ce, only improved P, but not Fe can exhibit approximately additive mixture toxicity, which can be adequately predicted by the simple Concentration Addition model. Our results suggested the important roles of P and Fe in assessing Y and Ce toxicity accurately.

Chlortetracycline hydrochloride removal by different biochar/Fe composites: A comparative study.

In the last years, the synthesis and applications of biochar/Fe composites have been extensively studied, but only few papers have systematically evaluated their removal performances. Herein, we successfully synthesized and structurally characterized Fe0, Fe3C, and Fe3O4-coated biochars (BCs) for the removal of chlortetracycline hydrochloride (CH). Evaluation of their removal rate and affinity revealed that Fe0@BC could achieve better and faster CH removal and degradation than Fe3C@BC and Fe3O4@BC. The removal rate was controlled by the O-Fe content and solution pH after the reaction. The CH adsorption occurred on the O C groups of Fe0@BC and the OC and OFe groups of Fe3C@BC and Fe3O4@BC. Electron paramagnetic resonance analysis and radical quenching experiments indicated that HO and 1O2/ O2- were mainly responsible for CH degradation by biochar/Fe composites. Additional parameters, such as effects of initial concentrations and coexisting anions, regeneration capacity, cost and actual wastewater treatment were also explored. Principal component analysis was applied for a comprehensive and quantitative assessment of the three materials, indicating Fe0@BC is the most beneficial functional material for CH removal.

A novel approach for determining the accurate debromination time in the ball-milling process of nonmetallic particles from waste printed circuit boards by computation.

Ball-milling technology is adopted for the debromination of nonmetallic particles of waste printed circuit boards. During the ball-milling process, too short ball-milling time causes insufficient debromination. Excessive ball-milling leads to the waste of resources and the destruction of the main structure of nonmetallic particles resin, unfavorable for the secondary utilization. However, how to determine debromination time of nonmetallic particles in ball-milling process has not been detailed studied. In this study, the ball-milling energy was coupled with the degradation energy of pentabromodiphenyl ether molecule to compute the time for each chemical bond to break. The ball-milling model was used to accurately compute effective mechanical ball-milling energy (1.234 × 10-3 J) generated by a single collision. The average bond energies of C‒O bond, C‒Br bond and C‒H bond (261.24, 302.05 and 489.50 kJ/mol) were analyzed by density functional theory. Under the conditions of 220 r/min and 1.2 g nonmetallic particles and NZVI (4:1). The C‒O bond, C‒Br bond, and C‒H bond fractured completely in turn at 2.25 h, 7.23 h (optimal debromination time), and 11.72 h. Based on the analysis of debromination pathways, it inferred that H2O, HBr, CH3Br, CH4, FeBr2, and graphite were generated. This paper develops a novel idea of the schedule of debromination time of nonmetallic particles, contributing to the directional removal of organic pollutants by ball-milling.

Biofilm for leaching precious metals from waste printed circuit boards using biocyanidation technology.

Presently, biocyanidation technology is being usually adopted to recover precious metals from an increasing quantity of waste printed circuit boards. The main aim of this work was to investigate the biofilm formation of Pseudomonas and its ability to leach precious metals. Based on batch experiments, strain 113 showed the highest biofilm-forming activity in optimal culture conditions of pH 7.0, 25 °C, and 1/25 NB medium among the Pseudomonas strains isolated. Both low concentrations of Cu2+ (500 ppm) and Ag+ (2.5 ppm) promoted biofilm formation. Under the optimal culture conditions for biofilm formation, the concentration of CN- was up to 5.0 ppm. In the continuous silver leaching experiment, the Ag+ concentration reached 4.0 ppm and the leaching efficiency was 14.7 % at 7 d. The results of this study may contribute to the construction of a bioreactor used for continuous leaching of waste printed circuit boards in an attempt to recover precious metals. Our results may also aid in the industrialization of biocyanidation technology.

Human exposure to PBDEs in e-waste areas: A review.

Polybrominated biphenyl ethers (PBDEs) are commonly added to electronic products for flame-retardation effects, and are attracting more and more attentions due to their potential toxicity, durability and bioaccumulation. This study conducts a sysmtematic review to understand the human exposure to PBDEs from e-waste recycling, especially exploring the exposure pathways and human burden of PBDEs as well as investigating the temporal trend of PBDEs exposure worldwide. The results show that the particular foods (contaminated fish, poultry, meat and breast milk) ingestion, indoor dust ingestion and indoor air inhalation may be key factors leading to human health risks of PBDEs exposure in e-waste recycling regions. Residents and some vulnerable groups (occupational workers and children) in e-waste recycling areas may face higher exposure levels and health risks. PBDE exposure is closely related to exposure level, exposure duration, e-waste recycling methods, and dietary customs. High levels of PBDEs are found in human tissues (breast milk, hair, blood (serum), placenta and other tissues) in e-waste areas, at far higher levels than in other areas. Existing data indicate that PBDE exposure levels do not present any apparent downward trend, and will possibly cause serious human diseases. More epidemiological studies are still needed to provide a solid basis for health risk assessment.

[Key processes and progress in phytomining of nickel contaminated soils: a review].

Phytomining technology cultivates hyperaccumulator plants on heavy metal contaminated soils, followed by biomass harvesting and incineration to recover valuable metals, offering an opportunity for resource recycling and soil remediation. Large areas of ultramafic soils, naturally rich in nickel (Ni), are present in numerous places around the world. As an environmentally friendly and cost-effective soil remediation technology, phytomining has a broad application prospect in such areas and thus has attracted great attention from global researchers. The key processes of phytomining include: (1) high-selectivity response of hyperaccumulator plants to Ni the underlying mechanisms involved in the rhizosphere; (2) underlying mechanisms of high-efficiency uptake and translocation of Ni in hyperaccumulators; and (3) resource recycling of high-added value Ni products from the Ni-rich bio-ore of hyperaccumulators. In recent 30 years, phytomining practices have successfully carried out in United States, Albania and Malaysia. However, the research and application of this technology in China are still in the fledging stage. This paper reviews the key processes and research progress of phytomining, and points out the bottleneck, to provide theoretical basis and technical guidance for phytomining.

A novel approach of accurately rationing adsorbent for capturing pollutants via chemistry calculation: Rationing the mass of CaCO3 to capture Br-containing substances in the pyrolysis of nonmetallic particles of waste printed circuit boards.

Pyrolysis technology is advised to dispose nonmetallic particles of waste printed circuit boards to produce oils and gases. During pyrolysis, brominated flame retardants in nonmetallic particles are converted into small-molecular Br-containing substances. They disperse into oil and gas so as to cause secondary pollution. Then, CaCO3 is suggested to be employed to capture the small-molecular Br-containing substances. However, too much CaCO3 will produce over solid wastes. Less CaCO3 might not capture the total Br-containing substances. How to ration the mass of adsorbent for capturing pollutant has not been detailed investigated. This paper found HBr was the main Br-containing substances during high temperature pyrolysis of nonmetallic particles. The capture process of HBr was detailed investigated by the method of computational chemistry. At the condition of 973 K and 100 Pa, HBr was captured by chemical reaction and physical absorption of CaCO3. Unit cell of CaCO3 reacted with two HBr to form CaBr2, and the generated unit cell of CaBr2 can adsorb 0.011 HBr. 0.0106 g CaCO3 can absorb all HBr produced by high temperature vacuum pyrolysis of 1 g nonmetallic particles. This paper contributes a novel approach to accurately ration the mass of adsorbents employed for capturing pollutants.

Model-based rationalization of mixture toxicity and accumulation in Triticum aestivum upon concurrent exposure to yttrium, lanthanum, and cerium.

Rare earth elements (REEs) often co-exist in the environment, but predicting their 'cocktail effects' is still challenging, especially for high-order mixtures with more than two components. Here, we systematically investigated the toxicity and accumulation of yttrium, lanthanum, and cerium mixtures in Triticum aestivum following a standardized bioassay. Toxic effects of mixtures were predicted using the reference model of Concentration Addition (CA), Ternary model, and Ternary-Plus model. Interactions between the REEs in binary and ternary mixtures were determined based on external and internal concentrations, and their magnitude estimated from the parameters deviated from CA. Strong antagonistic interactions were found in the ternary mixtures even though there were no significant interactions in the binary mixtures. Predictive ability increased when using the CA model, Ternary model, and Ternary-Plus model, with R2= 0.78, 0.80, and 0.87 based on external exposure concentrations, and R2= 0.72, 0.73, and 0.79, respectively based on internal concentrations. The bioavailability-based model WHAM-FTOX explained more than 88 % and 85 % of the toxicity of binary and ternary REE treatments, respectively. Our result showed that the Ternary-Plus model and WHAM-FTOX model are promising tools to account for the interaction of REEs in mixtures and could be used for their risk assessment.

Ecological influences of the migration of micro resin particles from crushed waste printed circuit boards on the dumping soil.

About 0.8 million tons of resin particles, which were generated from the recovery of waste printed circuit boards, were dumped on soil at Qingyuan city of China. Resin particles not only belong to micro plastic but also contain brominated flame retardants and heavy metals. There is little information about soil pollution caused by the dumped resin particles. This study found resin particles would transfer from soil surface into soil at least 10 mm downward for six months. Average content of bromine in soil within 10 cm exceeded 2500 mg/kg. The highest content of Pb, Zn, and Cu was 3450, 1143 and 1450 mg/kg, which were approximately 6.9, 2.3 and 3.6 times as much as Grade Ⅲ soil standard of China. Micro plastic, brominated flame retardants, and heavy metals made significant effects on soil bacterial community. Bacterial diversity was destroyed and the number of resistant bacteria increased obviously such as Acinetobacter, Pseudomonas and Paracoccus. This paper presented the ecological destroy of soil when the resin particles were deposited on soil surface. It also suggested the government to urgently manage the resin particles produced in the recovery of waste printed circuit boards.

Occurrence and distribution of neonicotinoid insecticides in surface water and sediment of the Guangzhou section of the Pearl River, South China.

Little information is available about the occurrence of neonicotinoid insecticides in surface water and sediment of the metropolitan regions around the rivers in China. Here we investigate the residual level of neonicotinoids in the Guangzhou section of the Pearl River. At least one or two neonicotinoids was detected in each surface water and sediment, and the total amount of neonicotinoids (∑5neonics) in surface water ranged from 92.6 to 321 ng/L with a geometric mean (GM) of 174 ng/L. Imidacloprid, thiamethoxam and acetamiprid were three frequently detected neonicotinoids (100%) from surface water. As for the sediment, total concentration was varied between 0.40 and 2.59 ng/g dw with a GM of 1.12 ng/g dw, and acetamiprid and thiacloprid were the common sediment neonicotinoids. Western and Front river-route of the Guangzhou section of the Pearl River suffered a higher neonicotinoids contamination than the Rear river-route, resulting from more effluents of WWTPs receiving, and intensive commercial and human activities. Level of residual neonicotinoids in surface water was significantly correlated with the water quality (p < 0.01), especially items of pH, DO and ORP, and nitrogen and phosphorus contaminants. Compared with reports about residual neonicotinoids in water and sediment previously, the metropolitan regions of the Guangzhou could be confronted with a moderate contamination and showed serious ecological threats (even heavier than the Pearl Rivers). Our results will provide valuable data for understanding of neonicotinoids contamination in the Pearl River Delta and be helpful for further assessing environmental risk of neonicotinoids.

Heat evolution and energy analysis of cyanide bioproduction by a cyanogenic microorganism with the potential for bioleaching of precious metals.

Precious metals were lost in the current technologies of recovering waste printed circuit boards (WPCBs). Microbe-produced cyanide is considered as an important lixiviant in bioleaching of precious metals from WPCBs. Enhancing cyanide production is the key to industrialization of bioleaching technology. This study identified the precursor form of biogenic cyanide, investigated the energy characteristics of cyanide synthesis, thermal change characteristics of cyanogenic culture, and the potential kinetic relationship between cyanide production and thermal change. We firstly found glycine anion [H2NCH2CO2]- was the precursor form of cyanide in microbial biocatalysis. The bond cleavage pathways from glycine anion to cyanide were analyzed by computation chemical. Results showed decomposition of glycine anion into cyanide was endothermic and non-spontaneous. Formations of [HN = CHCO2]- and -C≡N have an average energy barrier of 34.05 and 9.15 kcal/mol respectively, while formations of free radicals from anionic intermediates have an average barrier of 71.05 kcal/mol. Cyanide concentration began to increase from 0.48 to 5.27 mg/L when heat production was strongest. Temperature difference between sterile medium and cyanogenic culture reached 0.3 °C. Therefore, metabolic heat brought positive effect on cyanide biosynthesis.

A resource-utilization way of the waste printed circuit boards to prepare silicon carbide nanoparticles and their photocatalytic application.

A resource-utilization strategy of the waste PCBs was developed: preparation of high value-added silicon carbide (SiC) nanoparticles using the waste PCBs as both silica and carbon precursors. The preparation process contained three optimized steps: acid wash pretreatment with 3 mol L-1 nitric acid at 60 °C for 96 h, low-temperature pyrolysis at 500 °C to allow the epoxy resin to decompose into carbon, and high-temperature pyrolysis at 1600 °C (in situ carbothermal reduction) to gain pure SiC nanoparticles. The pseudo first-order reaction rate constant (k) of the p-n heterojunction of SiC/TiO2 towards the photocatalytic degradation of methylene blue was 0.0219 min-1, 3.42 and 3.98 times that of TiO2 and no acid washed-SiC/TiO2, respectively.

One-step sample processing method for the determination of perchlorate in human urine, whole blood and breast milk using liquid chromatography tandem mass spectrometry.

A one-step sample processing was developed to determine the levels of perchlorate in human urine, whole blood and breast milk by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Athena C18-WP column was used to separate and analyze perchlorate. Perchlorate and isotope-labeled perchlorate (Cl18O4-) internal standards were spiked in the sample matrix through vortex mixing, centrifugation, and filtration. The filtrate was collected and subjected to LC analysis. The developed method was validated for its reproducibility, linearity, trueness, and recovery. Satisfactory recovery of perchlorate ranged from 81% to 117% with intraday relative standard deviations (RSDs) (n = 3) and inter-day RSDs (n = 9) of 5-18% and of 5-16%, respectively. Good linearity (R2 ≥ 0.99) was observed. Limits of detection and quantification for perchlorate ranged from 0.06 µg/L to 0.3 µg/L and from 0.2 µg/L to 1 µg/L, respectively. Perchlorate concentrations were found in human urine (n = 38) and whole blood (n = 8) samples with the range of 6.5-288.6 µg/L and 0.3-2.8 µg/L, respectively. These results indicate the applicability of our developed method in determining perchlorate level in real samples. Moreover, this method is also highly reliable, sensitive and selective in detecting perchlorate in human urine, whole blood and breast milk samples and may be applicable to other matrixes i.e. saliva, serum, plasma, milk powder and dairy milk.

Occurrence, distribution and seasonal variation of five neonicotinoid insecticides in surface water and sediment of the Pearl Rivers, South China.

Occurrence and distribution of five neonicotinoids (NEOs) in surface water and sediment were studied in the Pearl Rivers, including three trunk streams, Dongjiang, Beijiang, Xijiang River (DR, BR and XR), South China. At least one neonicotinoid was detected in surface water and sediment of the Pearl Rivers, with imidacloprid (IMI) and thiamethoxam (THM) being the frequently detected NEOs. Total amount of NEOs (∑5neonics) in surface water and sediment ranged from 24.0 to 322 ng/L, and from 0.11 to 11.6 ng/g dw, respectively. Moreover, the order of contamination level of NEOs in the Pearl Rivers was as follows: XR > DR > BR for surface water, and BR > DR > XR for sediment. Local agricultural activities and effluents of wastewater treatment plants (WWTPs) could be major sources of NEOs in the Pearl Rivers. Solubilization and dilution of NEOs between surface water and sediment during different seasons (spring and summer) could be attributed to rainfall intensities or climate of the Pearl River Delta. An ecological risk assessment of the exposure to current environmental concentration of imidacloprid and ∑5NEOs suggests a threat to sensitive non-target invertebrates, including aquatic invertebrates. Results would provide a better understanding of NEOs contamination in the Pearl Rivers, as well as being a reliable dataset for decision-making in contamination control and environmental protection.