Jianfeng Bai

Characterization of Extreme Acidophile Bacteria (Acidithiobacillus ferrooxidans) Bioleaching Copper from Flexible PCB by ICP-AES

In order to improve copper leaching efficiency from the flexible printed circuit board (PCB) by Acidithiobacillus ferrooxidans, it is necessary to quantitatively measure the bacteria bioleaching copper under extreme acidic condition from flexible PCB. The inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is a very accurate way to analyze metals in solution; this paper investigated the optimal conditions for copper bioleaching by Acidithiobacillus ferrooxidans from flexible PCB through ICP-AES. The conditions included particle size of flexible PCB powder, quantity of flexible PCB powder, initial pH of culture medium, bacteria inoculation, bacteria activation time, and quantity of FeSO4·7H2O. Prior to ICP-AES measurement, culture solution was digested by aqua regia. The experimental results demonstrated that flexible PCB contained one main metal (copper); this was associated with the structure of flexible PCB. The optimization conditions were in 50 mL medium, flexible PCB 10 g/L, particle size of flexible PCB 0.42~0.84 mm, culture medium initial pH 2.5, bacteria inoculation 5%, bacteria activation time 5 d, and quantity of FeSO4·7H2O 30 g/L. Under the optimization condition, the leaching rate of copper was 90.10%, which was 42.4% higher than the blank group. For the ICP-AES determination, it reached a conclusion that the best corresponding wavelength (nm) of copper will be 224.7 (nm).

Lead recovery from scrap cathode ray tube funnel glass by hydrothermal sulphidisation

This research focused on the application of the hydrothermal sulphidisation method to separate lead from scrap cathode ray tube funnel glass. Prior to hydrothermal treatment, the cathode ray tube funnel glass was pretreated by mechanical activation. Under hydrothermal conditions, hydroxyl ions (OH–) were generated through an ion exchange reaction between metal ions in mechanically activated funnel glass and water, to accelerate sulphur disproportionation; no additional alkaline compound was needed. Lead contained in funnel glass was converted to lead sulphide with high efficiency. Temperature had a significant effect on the sulphidisation rate of lead in funnel glass, which increased from 25% to 90% as the temperature increased from 100 °C to 300 °C. A sulphidisation rate of 100% was achieved at a duration of 8 h at 300 °C. This process of mechanical activation and hydrothermal sulphidisation is efficient and promising for the treatment of leaded glass.

Arbuscular mycorrhizal fungi alleviate the heavy metal toxicity on sunflower ( Helianthus annuus L.) plants cultivated on a heavily contaminated field soil at a WEEE-recycling site

An 8-week pot experiment was conducted to investigate the growth and responses of sunflower (Helianthus annuus L.) to arbuscular mycorrhizal (AM) fungal inoculations on a heavily heavy metal (HM)-contaminated (H) soil and a lightly HM-enriched (L) soil, both of which were collected from a waste electrical and electronic equipment (WEEE)-recycling site. Compared with the L soil, the H soil induced significantly larger (P<0.05) concentrations of Cd, Cu, Pb, Cr, Zn and Ni in sunflower (except for root Cr and shoot Ni), which impaired the thylakoid lamellar folds in leaves. The biomasses and P concentrations of shoots and roots, as well as the total P acquisitions per pot were all significantly decreased (P<0.05). Both Funneliformis mosseae (Fm) and F. caledonium (Fc) inoculation significantly increased (P<0.05) root mycorrhizal colonization. For the L soil, AM fungal inoculations had no significant effects on the soil-plant system, except for a decrease of soil pH and increases of soil available P and DTPA-extractable Zn concentrations with the Fm-inoculated treatment. For the H soil, however, AM fungal inoculations significantly increased (P<0.05) the biomasses and P concentrations of shoots and roots, as well as the total P acquisitions per pot, and significantly reduced (P<0.05) the concentrations of HMs in shoots (except for Cu and Pb with Fm- and Fc- inoculated treatments, respectively) and alleviated the toxicity symptoms of HMs in thylakoid structure of leaves. AM fungal inoculations in the H soil also significantly increased (P<0.05) the shoot uptake of HMs (except for Cr), and tended to decrease the total concentrations of HMs in soils. This suggests the potential application of AM fungi for both reducing HM stress and promoting phytoextraction of HM-contaminated soils caused by WEEE recycling.

Improving arsenic mobility concentration from As-polluted soils by the functional strains

Arsenic (As) contamination has become the environment issue of global concern. In China, large area of farmland and the site soil were contaminated by As, which means that suitable remedying methods were urgently needed. Phytoremediation, as one of environment-friendly soil remediation techniques developed in recent years, shows a bright future for the remediation of As contaminated soils. However, phytoremediation efficiency needs to be enhanced further because of low concentration of bio-available As in the soils. A triangle flask culture experiment was carried out to study the effects of functional species, isolated from As-polluted soils, that could improve As mobility from the soil. These species included two bacilli, B1 and B2 (Brevibacillus) and two fungi, F1 (Trichoderma), F2 (Fusarium). They could transform the concentration of As fractionation in the soil sterilized by the method of 60Co-γ ray. Through the experiment, the concentrations of non-specifically-sorbed and specifically-sorbed As fractionation, and pH value of culture solution with inoculated treatment were higher than that with the control. Especially, the concentration of non-specifically-sorbed As fractionation in the treatment-inoculated species was 2 to 6 times higher than that of non-inoculation treatment. Moreover, two bacilli and two fungi could produce IAA, which was conducive to the plant survival when they were jointly used in remedying the As-contaminated soil.

Intercropping with sunflower and inoculation with arbuscular mycorrhizal fungi promotes growth of garlic chive in metal-contaminated soil at a WEEE-recycling site

Heavy metal (HM) pollution in agricultural soils due to the recycling of waste electrical and electronic equipment (WEEE) has become a serious concern, but most farmers cannot afford the economic losses of fallow land during remediation. Thus, it is imperative to produce low-HM crops while remediating the contaminated soils. A 17-week pot experiment was conducted to investigate the growth and HM (Cd, Cu, Pb, Cr, Zn, and Ni) acquisition of garlic chives (Allium tuberosum Rottl. ex Spreng.) intercropped with sunflower (Helianthus annuus L.) and inoculated with (I+M) or without (I-M) the arbuscular mycorrhizal (AM) fungus Funneliformis caledonium on a severely HM-contaminated soil that was collected from a WEEE-recycling site. Compared with the monoculture control, the I-M treatment significantly (P < 0.05) decreased Cd, Cu, Cr, Zn, and Ni concentrations in the shoots of chives through rhizosphere competition and HM (except Cr) transfer from the root to the shoot of chives, and increased the average shoot fresh weight (i.e., yield) of chives by 794% by alleviating HM toxicity. Compared with the I-M treatment, the I+M treatment significantly increased soil phosphatase activity as well as root mycorrhizal colonization of both sunflower and chives. The I+M treatment had no effect on the tissue P concentration of sunflower but elevated the average dry biomass (shoot plus root) and P acquisition level of sunflower by 179% and 121%, respectively. In addition, the I+M treatment significantly increased the P concentration in the root rather than in the shoot of chives and significantly increased the level of P acquisition by chives, increasing the average yield of chives by 229%. Simultaneously, the I+M treatment significantly increased the level of HM (except Cd) acquisition by sunflower, enhancing the rhizosphere competition by sunflower over chives, and further reducing the transfer of all six HMs from root to shoot in the chives, and inducing significant decreases in chive shoot HM concentrations compared with the monoculture control. Furthermore, the I+M treatment decreased the average total concentrations and increased the average DTPA-extractable concentrations of soil HMs. The results demonstrate the multifunctional role of AM fungi in the intercropping system for both vegetable production and phytoremediation on HM-contaminated soils.

Raman Spectroscopy Characterization of Dissolved Polysilicon Byproduct SiCl4 in Ionic Liquids

Silicon tetrachloride (SiCl4) is the main byproducts of the polysilicon industries. The dissolution behaviors of SiCl4 in imidazolium ionic liquid, including [Bmim]OTf, [Bmim]NTf2, [Hmim]NTf2, and [Omim]NTf2, were investigated for recycling Si from SiCl4. Raman spectroscopy was used to understand the combination between the ionic liquid and SiCl4, and the conductivity of ionic liquids in different conditions was determined. The results indicated that [Bmim]NTf2 exhibited a better SiCl4 dissolving capacity compared to [Bmim]OTf, longer alkyl chain lengths in the imidazolium cations of the ionic liquids exhibited a better performance in dissolving SiCl4, and [Bmim]NTf2 : PC = 1 : 2 exhibited the best conductivity. In addition, molecular bondings between C-Cl, Si-O-Si, and C-Si were formed between the ionic liquids and SiCl4.

Recycling of Polysilicon Byproduct SiCl4 Dissolved in Ionic Liquids

AbstractSilicon tetrachloride (SiCl4) is one of the primary by-products products of the polysilicon industries, which must also be handled with care, as it is both toxic and reactive. The dissolution of SiCl4 and electrodeposited of Si in ionic liquids (ILs) was investigated. Six kinds of ILs were examined as the solvents; the cations were 1-Butyl-3-methylimidazolium 1-butyl-3-methylimidazolium ([Bmim]+), 1-Hexyl-3-methylimidazolium ([Hmim]+), 1-Octyl-3-methylimidazolium ([Omim]+), N-butyl-3-methylpyridinium ([B3MePy]+), N-hexyl-3-methylpyridinium ([H3MePy]+), N-octyl-3-methylpyridinium ([O3MePy]+); the anion was bis[(trifluoromethyl)sulfonyl]imide ([NTf2]−). The results indicated that a decrease in the solubility of SiCl4 in ILs followed an increase in temperature. The presence of Si-O bonding between the ionic liquid and SiCl4 enhanced the SiCl4 dissolving capacity of in the ILs with anion of [NTf2]−. Longer alkyl chain lengths in the imidazolium and pyridinium cations of the ILs exhibited a better performance in dissolving SiCl4, due to the presence of C-Cl and C-Si formed between the ILs and SiCl4. Si was electrodeposited on a Ti plate under potential of 2.92V, of which a Si weight of up to 28.43 wt% was observed. The deposition product on the electrode is in the coexistence state of Si and SiOx due to the deposition conditions at ordinary temperature and pressure. Graphical AbstractRecycling of Polysilicon Byproduct SiCl4 by dissolution and electrodeposition in Ionic Liquids

Mechanochemical treatment of Cr(VI) contaminated soil using a sodium sulfide coupled solidification/stabilization process

In this research, mechanochemical reduction was carried out to remediate Cr(VI) contaminated soil, and the reduction effectiveness was evaluated by analyzing the corresponding leachable fraction obtained through the toxicity characteristic leaching procedure (TCLP) proposed by the EPA. The results indicated that mechanochemical reduction can efficiently reduce the Cr(VI) concentration in the leachate. Under a milling time of 2 h, milling speed of 500 rpm, ball-to-powder weight ratio of 14 and Na2S dosage of 5%, the Cr(VI) leaching concentration significantly decreased from 663.98 mg L-1 to 0.84 mg L-1, much lower than the regulatory limit of 5 mg L-1. In addition, the significant decrease in Cr(VI) was mainly due to the reduction of Cr(VI) to Cr(III), as supported by X-ray photoelectron spectroscopy (XPS). The mechanochemical reduction with mechanism proposed in this experiment may involve two major processes: solidification and reduction (stabilization).

Heavy metals in soil at a waste electrical and electronic equipment processing area in China

For the objective of evaluating the contamination degree of heavy metals and analysing its variation trend in soil at a waste electrical and electronic equipment processing area in Shanghai, China, evaluation methods, which include single factor index method, geo-accumulation index method, comprehensive pollution index method, and potential ecological risk index method, were adopted in this study. The results revealed that the soil at a waste electrical and electronic equipment processing area was polluted by arsenic, cadmium, copper, lead, zinc, and chromium. It also demonstrated that the concentrations of heavy metals were increased over time. Exceptionally, the average value of the metalloid (arsenic) was 73.31 mg kg−1 in 2014, while it was 58.31 mg kg−1 in the first half of 2015, and it was 2.93 times and 2.33 times higher than that of the Chinese Environmental Quality Standard for Soil in 2014 and the first half of 2015, respectively. The sequences of the contamination degree of heavy metals in 2014 and the first half of 2015 were cadmium > lead > copper > chromium > zinc and cadmium > lead > chromium > zinc > copper. From the analysis of the potential ecological risk index method, arsenic and cadmium had higher ecological risk than other heavy metals. The integrated ecological risk index of heavy metals (cadmium, copper, lead, zinc, and chromium) and metalloid (arsenic) was 394.10 in 2014, while it was 656.16 in the first half of 2015, thus documenting a strong ecological risk.

The Regulatory Roles of MicroRNA in Effects of 2,2'4,4'-Tetrabromodiphenyl Ether (BDE47) on the Transcriptome of Zebrafish Larvae

The developmental neurotoxicity caused by environmental pollutants has received great concern; however, there were still barely known about the underlying toxic mechanisms, especially the influence of varieties of regulatory factors such as microRNA (miRNA). A representative flame retardant, 2,2′,4,4′-tetrabromodiphenyl ether (BDE47), was found to disrupt zebrafish development in visual perception and bone formation in previous study, thus here we investigated its effects on miRNA expression profiling of 6 days post fertilization (dpf) zebrafish larvae by deep sequencing. To overcome the shortage of zebrafish miRNA annotation, multiple data processing approaches, especially constructed network based on the interactions between miRNAs and enrichment terms, were adopted and helped us acquire several validated zebrafish miRNAs and two novel miRNAs in BDE47-induced effects, and identify corresponding biological processes of the miRNAs. Among them, miR-735 was supposed to play essential roles in larval sensory development according to analysis results. Our study also provided an effective strategy for analyzing biological effects on non-mammalian miRNAs with limited basic information.