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Life cycle assessment (LCA) was carried out by SimaPro 7.3 to study the environmental impact of a lab-scale batch subcritical water decomposition operation for a kilogram of Perfluorooctane sulfonic acid (PFOS) waste treatment in this study, a proven process for the decomposition of PFOS pollutants with high concentration. This LCA focuses on not only the main environmental factors from emissions of toxic pollutants, but also the influence from technical characteristics of the iron-induced subcritical water technology including energy and substances consumption during the subcritical water decomposition treatment process. The IMPACT 2002+ environmental model was used to evaluate the 15 midpoint and 4 end-point environmental damages. It was found that the energy consumption to sustain the high temperature (350 A degrees C) and high pressure (23 MPa) in the subcritical water process contributes 99.8 % of the damages. The total negative impact of the SCWD process for 1 kg of PFOS waste treatment to human health, ecological quality, climate change and resources amounts to 1.11 x 10(-3), 8.43 x 10(-5), 9.76 x 10(-4), 9.05 x 10(-4) Pt, respectively. And the improvement of energy efficiency and catalytic effectiveness are two important factors to reduce the environmental impact from the SCWD process for the treatment of PFOS waste.

Waste printed circuit boards (WPCBs) contain high amount of brominated flame retardants and heavy metals which may bring a series of environmental and health problems. In the present study, an effective and benign process using sub- and supercritical water (sub/SCW) to simultaneously degrade brominated epoxy resin and recover metals from WPCBs was developed. Experiments were performed in a batch-type reactor with temperatures ranging from 200 to 400 °C, water adding amounts from 10 to 40 ml and holding times from 30 to 240 min. The results showed that brominated epoxy resins (BERs) could be quickly and efficiently decomposed under sub/SCW condition. The debromination rate was 97.8% by controlling the temperature, water adding amount and holding time at 400 °C, 40 ml and 120 min, respectively. Most of the bromine was changed into HBr and around 97.7% was enriched in water. Meanwhile, bromine-free oil was obtained of which the main compositions were phenol (58.5%) and 4-(1-methylethyl)-phenol (21.7%). After the sub/SCW treatments, the glass fibers and copper foils in the residue can be easily liberated and recovered respectively. The copper recovery rate reached 98.11% in the purities of 96.74% (grain size >2.0 mm) and 92.74% (0.147–2.0 mm). This study provides an efficient and green approach for WPCBs recycling.

The current study was carried out to develop an environmental benign process for direct recovery of palladium (Pd) and silver (Ag) from waste printed circuit boards (PCBs) powder. The process ingeniously combined supercritical water oxidation (SCWO) and supercritical carbon dioxide (Sc-CO2) extraction techniques. SCWO treatment could effectively enrich Pd and Ag by degrading non-metallic component, and a precious metal concentrate (PMC) could be obtained, in which the enrichment factors of Pd and Ag reached 5.3 and 4.8, respectively. In the second stage, more than 93.7% Pd and 96.4% Ag could be extracted from PMC by Sc-CO2 modified with acetone and KI-I2 under optimum conditions. Mechanism study indicated that Pd and Ag extraction by Sc-CO2 was a complicated physiochemical process, involving oxidation, complexation, anion exchange, mass transfer and migration approaches. Accordingly, this study established a benign and effective process for selective recovery of dispersal precious metals from waste materials.

This work investigated various supercritical water oxidation (SCWO) systems, i.e. SCWO1 (only water), SCWO2 (water + H 2 O 2 ) and SCWO3 (water + H 2 O 2 /NaOH), for waste printed circuit boards (PCBs) detoxification and recycling. Response surface methodology (RSM) was applied to optimize the operating conditions of the optimal SCWO3 systems. The optimal reaction conditions for debromination were found to be the NaOH of 0.21 g, the H 2 O 2 volume of 9.04 mL, the time of 39.7 min, maximum debromination efficiency of 95.14%. Variance analysis indicated that the factors influencing debromination efficiency was in the sequence of NaOH > H 2 O 2 > time. Mechanism studies indicated that the dissociated ions from NaOH in supercritical water promoted the debromination of brominated epoxy resins (BERs) through an elimination reaction and nucleophilic substitution. HO 2 , produced by H 2 O 2 could induce the oxidation of phenol ring to open (intermediates of BERs), which were thoroughly degraded to form hydrocarbons, CO 2 , H 2 O and NaBr. In addition, the alkali-silica reaction between OH − and SiO 2 induced the phase transformation of glass fibers, which were simultaneously converted into anorthite and albite. Waste PCBs in H 2 O 2 /NaOH improved SCWO system were fully degraded into useful products and simultaneously transformed into functional materials. These findings are helpful for efficient recycling of waste PCBs.

In this work, an effective and environmentally friendly process for the recovery of cobalt (Co) and lithium (Li) from spent lithium-ion batteries (LIBs) and simultaneously detoxification of polyvinyl chloride (PVC) in subcritical water was developed. Lithium cobalt oxide (LiCoO2) power from spent LIBs and PVC were co-treated by subcritical water oxidation, in which PVC served as a hydrochloric acid source to promote metal leaching. The dechlorination of PVC and metal leaching was achieved simultaneously under subcritical water oxidation. More than 95% Co and nearly 98% Li were recovered under the optimum conditions: temperature 350°C, PVC/LiCoO2 ratio 3:1, time 30min, and a solid/liquid ratio 16:1 (g/L), respectively. Moreover, PVC was completely dechlorinated at temperatures above 350°C without any release of toxic chlorinated organic compounds. Assessment on economical and environmental impacts revealed that the PVC and LiCoO2 subcritical co-treatment process had significant technical, economic and environmental benefits over the traditional hydrometallurgy and pyrometallurgy processes. This innovative co-treatment process is efficient, environmentally friendly and adequate for Co and Li recovery from spent LIBs and simultaneous dechlorination of PVC in subcritical water.

In this study, a novel two-stage process, i.e. first stage for hydrogen species generation at 150 °C and second stage for PCB dechlorination at 330 °C, was developed for efficient PCB degradation in subcritical water with nanoscale Ni/Fe particles. The obtained results showed that over 92% of PCBs was completely converted into 1-alkyl-benzenes during this process. The addition of hydrogen donors could greatly enhance PCB dechlorination in descending order: oxalic acid ≈ HAc > NaH 2 PO 4 ≈ KH 2 PO 4 . The anion introduced along with H + played the crucial role in overall dechlorination process due to the undesired reaction between anion and reactive nanoscale Ni/Fe. Oxalic acid was quite effective for the generation of hydrogen species by supply more available H + without undesired side reaction. In contrast, phosphate could react with Ni/Fe rapidly to form complex precipitates on particle surface and thereby block the reactive sites of particle following suspension of dechlorination. In addition, low 150 °C at first stage as compared to 330 °C at second stage favored the dissolution and adsorption of hydrogen on Ni surface for catalyzing to form more reactive hydrogen species used for rapid dechlorination.

Chemical activation is a widespread method for activated carbon (AC) preparation, but the removal and recycle of activator from the carbon product are generally a nuisance process. In this study, an environmental benign process, called modified vacuum pyrolysis (MVP) process, was developed for AC production and simultaneous recovery of the activator. The process included two steps: (1) carbonization and activation stage in a vacuum condition; (2) zinc recovery stage in a special temperature and pressure range. In the MVP process, over 99.99 % of the zinc used for activation was recovered in the form of zinc chloride and metallic zinc. The resultant ACs with basic and hydrophobic surface properties displayed higher adsorption capacity for phenol than that of carbons obtained by traditional pyrolysis method. The main merit of the MVP process was that there was no wastewater generation during the whole procedure. Consequently, the experimental data obtained in the present study provided scientific basis for zinc chloride recovery by vacuum pyrolysis during ACs production process.

Waste printed circuit boards (WPCBs) contain high amount of brominated flame retardants that may bring a series of environmental and health problems. In the present study, an effective and environmental-friendly process using sub-and supercritical water (sub/SCW) to simultaneously degrade brominated epoxy resin and recover metals from WPCBs was developed. The results showed that brominated epoxy resins (BERs) can be quickly decomposed under SCW condition. Most of the bromine was changed into HBr and enriched in water. Meanwhile, bromine-free oil was obtained of which the main compositions were phenol and 4-(1-methylethyl)-phenol. This study provides an efficient and green approach for WPCBs recycling. (C) 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China.

To evaluate the potential preventive effect of probiotics on ventilator-associated pneumonia (VAP). This was an open-label, randomized, controlled multicenter trial involving 235 critically ill adult patients who were expected to receive mechanical ventilation for ≥48 h. The patients were randomized to receive (1) a probiotics capsule containing live Bacillus subtilis and Enterococcus faecalis (Medilac-S) 0.5 g three times daily through a nasogastric feeding tube plus standard preventive strategies or (2) standard preventive strategies alone, for a maximum of 14 days. The development of VAP was evaluated daily, and throat swabs and gastric aspirate were cultured at baseline and once or twice weekly thereafter. The incidence of microbiologically confirmed VAP in the probiotics group was significantly lower than that in the control patients (36.4 vs. 50.4 %, respectively; P = 0.031). The mean time to develop VAP was significantly longer in the probiotics group than in the control group (10.4 vs. 7.5 days, respectively; P = 0.022). The proportion of patients with acquisition of gastric colonization of potentially pathogenic microorganisms (PPMOs) was lower in the probiotics group (24 %) than the control group (44 %) (P = 0.004). However, the proportion of patients with eradication PPMO colonization on both sites of the oropharynx and stomach were not significantly different between the two groups. The administration of probiotics did not result in any improvement in the incidence of clinically suspected VAP, antimicrobial consumption, duration of mechanical ventilation, mortality and length of hospital stay. Therapy with the probiotic bacteria B. Subtilis and E. faecalis are an effective and safe means for preventing VAP and the acquisition of PPMO colonization in the stomach.

Fly ash from hazardous waste incinerators (HWIs) was characterized by higher concentration of volatile heavy metals when compared with the ash from municipal solid waste incinerators. Inspite of its high leaching potential of toxic metals and high risk of heavy metal release in landfills, few studies are currently implemented for the detoxification of HWI fly ash. The feasibility of vacuum-aided heat treatment (VAHT) for high toxic HWI fly ash was investigated to fulfil the requirements of environmental sound management of HWI fly ash. Also, the behavior of major toxic heavy metals Ba, Cd, Cr, Cu, Pb, and Zn during the treatment and their leaching properties after VAHT were studied in detail. Laboratory scale study showed that VAHT could effectively eliminate 100% of the Cd, 93.1% of the Pb, and 81.0% of the Zn under conditions of 900 degrees C, 10 Pa, and 4 h. F-test showed that pressure is the significant factor for the removal of Cd and Pb, whereas temperature is a remarkable factor for Sn and Zn. Sequential chemical extraction analysis shows that VAHT can largely remove the heavy metals that are exchangeable, bound to carbonate, and bound to Fe-Mn oxides, correspondingly decreasing the environmental leaching toxicity of heavy metals from HWI fly ash.

The present study was carried out to better understand the reactivity of nanoscale Ni/Fe particles towards the dechlorination of polychlorinated biphenyls (PCBs) contained in waste capacitor oil and the corresponding dechlorination mechanism in subcritical water. Batch experiments showed that nanoscale Ni/Fe particles could more quickly and effectively dechlorinate PCBs stepwise as compared to nanoscale zerovalent iron (n-ZVI) and nano-Ni 0 . The dechlorination products were much more centralized in the presence of Ni/Fe than other particles, and biphenyl, cyclohexyl-benzene and 1-alkyl-benzenes were the main products which can be used as raw chemicals. Moreover, catalytic hydrogenation by virtue of introduction of Ni 0 as catalyst can not only result in rapid dechlorination but also avoid formation of toxic chlorinated hydrocarbons. The reactivity of nanoscale Ni/Fe can retain in subcritical water for rapid catalytic hydrodechlorination. This process poses the prospect of recovery of valuable chemicals in the course of disposal of hazardous PCB-containing capacitor oil or transformer oil.

The feasibility of hydrothermal char (HTC), a byproduct from biomass hydrothermal liquefaction for bio-oil production, as raw material for preparation of porous carbons was investigated in the present study. The resultant HTC-derived porous carbons were characterized and utilized as adsorbents for copper (II) and phenol removal from aqueous solution. Compared with porous carbons using pyrolytic char as precursor, the HTC-derived porous carbons exhibited unique textural features, e.g., narrow pore size distribution, high surface area and large pore size. In addition, FT-IR analysis confirmed that substantial amount of ketene groups existed on the surface of the HTC-derived porous carbons. As the adsorbents, the copper (II) adsorption onto HTC-derived carbons was strongly affected by the pH value of the solution in comparison with phenol adsorption. The carbons derived from pinewood and rice husk HTC exhibited high adsorption capacity of 83.88 and 39.30 mg/g for phenol and 25.18 and 22.62 mg/g for copper (II), respectively. The adsorption data for copper (II) and phenol onto the carbon adsorbents could be well described by Langmuir and Freundlich models. In comparison with pinewood sawdust HTC-derived carbon, the adsorption onto rice husk HTC-derived carbon preferentially followed Freundlich model due to the presence of silica on the surface.

A novel process for crystalline silicotitanate (CST) synthesis was developed using waste cathode ray tube (CRT) panel glass as silicon source. The key trait of the process was to extract most of the silicon out of the glass for CST preparation, but leave Ba and Sr in the residue which had the potential to be employed as raw material for metallic Ba and Sr metallurgy. In the synthesis process, waste CRT panel glass was firstly treated by supercritical water (SCW)-NaOH solution for Si extraction, then sol-gel and hydrothermal treatments were used for CST preparation. 80% of Si in the glass could be extracted into the solution, while Sr and Ba were enriched in the residue in the form of Sr(2)SiO(4) and Ba(2)Si(3)O(8), respectively. Sr and Ba contents in the residue were 2-3 times higher than those in the raw glass. SEM, XRD and TEM results indicated that CST was successfully synthesized. Ion exchanging experiments showed that the batch distribution coefficient of the synthesized CST to Cs(+) was up to 1.2 x 10(4) mL/g at pH 0.26. (C) 2010 Elsevier B.V. All rights reserved.

A novel process for the preparation of Fe3O4-loaded activated carbon (MY) was developed using waste biomass. The key point of the synthetic strategy was that the carbonization, activation and Fe3O4 loading were accomplished simultaneously. The low-cost composite was characterized and used as an adsorbent for arsenate removal from water. The results showed that the Fe3O4 particles were uniformly deposited on the surface of the composite. The composite exhibited high surface area of 349 m2/g, pore volume of 0.20 cm3/g and iron of 39 wt.% for arsenate adsorption. As an adsorbent, higher temperature favored the adsorption capacity and the adsorption process was well fitted by pseudo-second-order model. The composite showed an excellent adsorption capability for arsenate with a maximum adsorption capacity of 204.2 mg/g at pH 8.0 and the adsorption process followed the Freundlich isotherm model well. In addition, the composite exhibited a saturation magnetization of 47.67 emu/g, which allowed it to be easily recovered by an external magnetic field after the adsorption process.

Heterogeneous photo-Fenton process using an amorphous FeOOH as catalyst was studied to degrade Methyl Orange (MO) dye in aqueous solution. The amorphous FeOOH was prepared by dissolution and precipitation using a high iron-containing fly ash as raw material. The ash not only provided iron source but also acted as a supporter of amorphous FeOOH. Coating the fly ash particles with the amorphous FeOOH significantly enhanced the removal of MO, and 2.5 g of catalyst was sufficient to degrade 50 mg MO from 1 l of aqueous solution at pH 7.0 after 80 min. Oxidant concentration, solution pH, UV/dark/sunlight and recycling of the catalyst were investigated in order to evaluate the photo-Fenton effects. Moreover, variations of particle size before and after preparation, separation of solid–liquid and stability of the amorphous FeOOH in the catalyst were studied. It was testified that the amorphous FeOOH on the surface of fly ash was stable and the Fenton catalyst was easily separated from the aqueous system.

Two types of pinewood chars, hydrothermal char (H300) and pyrolytic char (P700) from biomass-toenergy conversion were characterized and used as adsorbent for the copper removal from aqueous solution. The result showed that the pinewood underwent a deeper carbonization during pyrolysis process and more activated sites available and stable carbon-oxygen complex existed after hydrothermal treatment. Comparing with raw pinewood, hydrothermal treatment increased 95% total oxygen-containing groups ( carboxylic, lactone and phenolic group) while 56% oxygen-containing groups decreased after pyrolysis process. SEM analysis indicated that both hydrothermal and pyrolytic processes developed rough surface with new cavities on the chars, and the BET surface area were 21 and 29 m(2)/g for H300 and P700, respectively. Although H300 had lower surface area, its adsorption capacity for copper was much higher than P700 since ion-exchange reaction was the predominant removal mechanism by H300, while physical adsorption dominated by P700. The adsorption data could be well described by Langmuir isotherm model for copper onto both H300 and P700. (C) 2009 Elsevier Ltd. All rights reserved.

It is difficult for separation and reutilization of Cu in waste printed circuit boards (PCBs) due to the heterogeneous mix of polymer materials, multiple kinds of metals and glass fiber. In this study, waste PCBs were pretreated by supercritical water oxidation (SCWO), then introduced into an electrokinetic (EK) system with nano-TiO2 suspension as catholyte. In the EK process, Cu could be leached and reduced separately from the complicated multi-metal system in cathode compartment, and Cu2O could be formed in nano-size on TiO2 surface. The properties of the composite catalysts Cu2O/TiO2 were examined and their photocatalytic efficiencies were determined for methylene blue (MB) degradation. The results indicated that the catalytic effect increased with increasing EK preparation time but decreased afterwards. The most effective catalyst (4.53 wt.% Cu2O/TiO2), whose degradation ability was found to be much higher in comparison with commercial P25, was prepared by 6 h EK treatment. It was found that the loading of Cu2O on TiO2 surface could greatly enhance the photocatalytic effect of the catalyst. It is believed that the EK technology is effective and green for direct preparation of high value-added Cu nanocomposite materials from waste PCBs or other Cu-rich wastes. (C) 2009 Elsevier B.V. All rights reserved.

In this work, medical waste (MW) incinerator fly ashes from different types of incinerators were subjected to supercritical water (SCW) and SCW + H 2 O 2 (SCWH) treatments. Sequential extraction experiments showed that, after SCW treatment, heavy metals in exchangeable and carbonate forms in the ashes could be transferred into other relatively stable forms, e.g., Ba and Cr into residual fraction, Cu and Pb into organic matter fraction. SCWH treatment could stabilize heavy metals in Fe–Mn oxides and residual fractions. However, the behavior of As was quite different from heavy metals, which could be leached out from residue fraction after SCW and SWCH treatments. The leached As tended to absorb onto Fe–Mn oxides and organic matters under near neutral environment, but it could react with Ca 2+ at lower pH, increasing the mobility of this element. Therefore, it is necessary to neutralize acidic ash to near neutral condition before subjecting it to SCW and SCWH treatments so as to effectively stabilize hazardous elements in the ash. Consequently, it is believed that SCWH treatment is an effective alternative for hazardous elements detoxification in MW fly ash.

A novel adsorbent for arsenic (V) removal from wastewater was developed through simple chemical processes using a special iron-abundant fly ash. In the synthesis process. the inherent iron in the fly ash was rearranged and loaded on the surface of the fly ash by dissolution and precipitation processes. The adsorbent (HIOFAA) was characterized by XRD, FT-IR, SEM, LPS and BET surface area. The results showed that porous amorphous FeOOH was loaded on the surface of HIOFAA successfully. The BET surface area of HIOFAA was 22 times of those of the original fly ash, and furthermore. the mean particle size of HIOFAA increased 3 times compared to the raw fly ash, thus effectively accelerated the solid/liquid separation after the adsorptive treatment. The adsorption isotherm data could be well described by Langmuir isotherm model, and the adsorption capacity for arsenic removal was 19.46mg g(-1). Accordingly, it is believed that the adsorbent developed in this study is effective for arsenic polluted wastewater treatment (C) 2009 Elsevier B.V. All rights reserved.

The printed circuit boards (PCBs) contains large number of heavy metal such as Cd, Cr, As, Ni, Zn and Mn. In this study, the use of electrokinetic (EK) treatment with different assisting agents has been investigated to recover the heavy metals from waste PCBs, and the effectiveness of different assisting agents (HNO(3), HCl, citric acid) was evaluated. The PCBs were first pre-treated by supercritical water oxidation (SCWO) process, then subjected to EK process. The heavy metal speciation, migration and recovery efficiency in the presence of different assisting agents during EK process were discussed. The mass loss of Cd, Cr, As and Zn during the SCWO process was negligible, but approximately 52% of Ni and 56% of Mn were lost in such a process. Experimental results showed that different assisting agents have significant effect on the behavior and recovery efficiency of different heavy metals. HCl was highly efficient for the recovery of Cd in waste PCBs due to the low pH and the stable complexation of Cl(-). Citric acid was highly efficient for the recovery of Cr, Zn and Mn. HNO(3) was low efficient for recovery of most heavy metals except for Ni. (C) 2009 Elsevier B.V. All rights reserved.

Incineration of medical waste (MW) is an important alternative way for disposal of this type of hazardous waste, especially in China because of the outbreak of severe acute respiratory syndromes (SARs) in 2003. Thus, far, fly ash has received much attention but less attention has been paid to bottom ash. In this study, bottom ash samples were collected from a typical MW incinerator, and typical pollutants including heavy metals and polycyclic aromatic hydrocarbons (PAHs) in the ash were examined. X-ray fluorescence spectroscopy results indicated that CaO, SiO(2) and Al(2)O(3) were the main components of the bottom ash. Inductively coupled plasma-optical emission spectroscopy showed that the ash contained large amounts of heavy metals, including Zn, Ti, Ba, Cu, Pb, Mn, Cr, Ni and Sn. Most of the heavy metals (e.g., Ba, Cr, Ni, and Sn) presented in the residual fraction; whereas Mn, Pb and Zn presented in Fe-Mn oxides fraction, and Cu in organic-matter fraction. Toxicity characteristic leaching procedure tests indicated that the leached amounts of heavy metals were well below the limits. The sum of 16 US EPA priority PAHs (Sigma PAHs) varied from 10.30 to 38.14 mg kg(-1), and the total amounts of carcinogenic PAHs ranged between 4.09 and 16.95 mg kg(-1), exceeding the limits regulated by several countries. This research provides basic information for the evaluation of the environmental risk of MW incinerator bottom ash.

Silver (Ag) nanoparticles were obtained when Ag microparticles were exposed to an electron beam in a transmission electron microscope (TEM). Results from TEM characterization indicated that the morphologies of the prepared Ag nanoparticles were quasi-circular, and the sizes were mainly in the range of 5–60 nm. The effect of irradiation time (t) on size and distribution of Ag nanoparticles was investigated. It was found that the sizes of Ag nanoparticles increased with the increase of t. The bigger Ag nanoparticles were near the Ag microparticle and the smaller ones were far from it. In addition, these Ag nanoparticles were monodisperse. This approach offered a new route for preparing Ag nanoparticles under electron beam irradiation, and the forming process of Ag nanoparticles was explained by the nucleation-growth mechanism.

An effective and benign process for copper and lead recovery from waste printed circuit boards (PCBs) was developed. In the process, the PCBs was pre-treated in supercritical water, then subjected to electrokinetic (EK) process. Experimental results showed that supercritical water oxidation (SCWO) process was strong enough to decompose the organic compounds of PCBs, and XRD spectra indicated that copper and lead were oxidized into CuO, Cu(2)O and beta-PbO(2) in the process. The optimum SCWO treatment conditions were 60 min, 713 K, 30 MPa, and EK treatment time, constant current density were 11 h, 20 mA cm(-2) respectively. The recovery percentages of copper and lead under optimum SCWO + EK treatment conditions were around 84.2% and 89.4%, respectively. In the optimized EK treatment, 74% of Cu was recovered as a deposit on the cathode with a purity of 97.6%, while Pb was recovered as concentrated solutions in either anode (23.1%) or cathode (66.3%) compartments but little was deposited on the electrodes. It is believed that the process is effective and practical for Cu and Pb recovery from waste electric and electronic equipments. (C) 2008 Elsevier B.V. All rights reserved.

A novel process for the treatment of hazardous waste Cathode Ray Tube (CRT) glass, based on self-propagating reaction, was proposed. In the process, various types of CRT glass powders were blended with suitable amount of ferric oxide and magnesium, and the mixtures could generate self-propagating reaction once locally ignited by a thermal source. Generally, the self-propagating reaction could be well maintained when the CRT glass content in the mixture was no more than 60 wt.%, and the combustion wave velocity and maximum combustion temperature decreased along with the increase in glass amount. XPS experiments showed that heavy elements in the final products became more stable and were solidified during the process. Leaching tests demonstrated that heavy metals in the final products fulfilled the environmental regulations of USEPA. It is supposed that the detoxified products have the potential of being used as construction materials.

Silver (Ag) nanoparticles were prepared using Ag microparticles as precursors in supercritical water (SCW). The effect of reaction time on preparing Ag nanoparticles was investigated. The obtained products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The results indicated that, with the increase of reaction time, Ag microparticles prepared by calcination method with the sizes > 2 μm remained after SCW treatment because of their high crystallinity, but those with the sizes

Waste ashes from three types of hospital waste (HW) incinerators, built in SARS (Severe Acute Respiratory Syndrome) period and currently running in China, were collected and polycyclic aromatic hydrocarbons (PAH) properties in the ashes were investigated. The mean summation PAH levels in the waste ashes varied widely from 4.16 mg kg(-1) to 198.92 mg kg(-1), and the mean amounts of carcinogenic PAHs ranged from 0.74 to 96.77 mg kg(-1), exceeding the limits regulated by several countries. Among the three types of incinerators, two medium-scale incinerators generated relatively high levels of PAHs (mean summation PAH 22.50 and 198.92 mg kg(-1)) compared to small-scale and large-scale incinerators (mean summation PAH 4.16 and 16.43 mg kg(-1)). Bottom ashes were dominated by low molecular weight PAHs (LM-PAH; containing two- to three-ringed PAHs) and medium molecular weight PAHs (MM-PAH; containing four-ringed PAHs), while fly ashes were abundant in MM-PAH and high molecular weight PAHs (HM-PAH, containing five- to six-ringed PAHs). Statistical analysis indicated that there was a positive relationship (R2=0.88) between organic matter and total PAHs thus it has the potential to be used as an indicator for PAHs in HW ashes. Moreover, it was found that PAHs in the ashes correlated highly with some metallic elements either positively (e.g. Fe, Ti, Mg) or negatively (Ca), indicating that these elements might promote or prevent PAH formation during HW combustion. Although bottom ash resulted from HW incinerators has not been classified as hazardous material, the results of this study indicated that this type of waste ash contained high levels of PAHs thus need special treatment before landfill.

Photocatalytic oxidation of arsenite and simultaneous removal of the generated arsenate from aqueous solution were investigated. The whole process was performed using an adsorbent developed by loading iron oxide and TiO2 on municipal solid waste melted slag. The loading was carried out through chemical reactions and high-temperature process. In the removal process, arsenite was first oxidized to arsenate, and then was removed by adsorption. The oxidation of arsenite was rapid, but the adsorption of the generated arsenate was slow. A concentration of 100 mg l(-1) arsenite could be entirely oxidized to arsenate within 3 h in the presence of the adsorbent and under UV-light irradiation, but the equilibrium adsorption of the generated arsenate needed 10 h. Arsenite could also be oxidized to arsenate only by UV-light, but the reaction rate was approximately 1/3 of that of the photocatalyzed reaction. Both acidic and alkaline conditions were favorable for the oxidation reaction, and the optimum pH value for the oxidation and adsorption was proposed to be around 3. To oxidize and remove original 20 mg l(-1) or 50 mg l(-1) arsenite from aqueous solution, the necessary adsorbent amount was 2 g l(-1) or 5 g l(-1), respectively. Furthermore, the surface properties of the adsorbent were examined and the oxidation mechanism of arsenite was discussed. It is believed that the adsorbent developed in this study is efficient, cost-effective and environment-friendly for application in arsenic-contaminated wastewater treatment.

This work examined the extraction properties of metallic elements from municipal incinerator fly ash under hydrothermal conditions. The ash was firstly pre-washed by distilled water, then subjected to hydrothermal treatments. The pre-washing process was effective for Na, K, Ca extraction with extraction percentages of 67%, 76% and 48%, respectively. The optimum contact time was 30 min for the pre-washing process. Five types of acids were tested for the extraction experiments and hydrochloric acid was found to be most effective for metal extraction from the ash. Compared to room condition, hydrothermal treatment accelerated the dissolution of the ash, thus promoted the reaction of acid with hazardous metals such as Cr, Cd, Pb, and furthermore, the consumption speed of acid was slowed down under hydrothermal condition. The acid simultaneously reacted with all the metal in the ash under hydrothermal condition but preferentially reacted with Ca at room condition. The optimum hydrothermal treatment temperature, time and liquid/solid ratio were 150 °C, 5 h and 10:1 (ml:g), respectively.

An effective adsorbent for arsenic removal from aqueous system was synthesized by loading iron(III) oxide on municipal solid waste incinerator melted slag. The loading was accomplished via chemical processes and thermal coating technique. The key point of the technique was the simultaneous generation of amorphous FeOOH sol and silica sol in-situ and eventually led to the formation of Fe-Si surface complexes which combined the iron oxide with the melted slag tightly. The surface morphology of the iron oxide-loaded slag was examined and the loading mechanisms were discussed in detail. The adsorbent was effective for both arsenate and arsenite removal and its removal capabilities for As(V) and As(III) were 2.5 and 3 times of those of FeOOH, respectively. Both affinity adsorption and chemical reactions contributed to arsenic removal. The effects of solution pH, contact time, arsenic concentration and adsorbent dosage on arsenic removal were examined and the optimum removal conditions were established. Furthermore, leaching of hazardous elements such as Cr(VI), As, Se, Cd and Pb from the adsorbent at a pH range of 2.5-12.5 was below the regulation values. Accordingly, it is believed that the iron oxide-loaded slag developed in this study is environmentally acceptable and industrially applicable for wastewater treatment.

Various types of activated carbons were developed from organic sewage sludge (SS) using H(2)SO(4), H(3)PO(4) and ZnCl(2) as chemical activation reagents, and the removal of Hg(II) from aqueous solution by these carbons was effectively demonstrated. The quality of the activated carbons was dramatically improved owing to chemical activation. ZnCl(2) activated carbon had the highest capability for Hg(II) adsorption, followed by H(3)PO(4) and H(2)SO(4) activated carbons. The adsorption was greatly affected by Hg(II) concentration, solution pH and carbon dosage, and followed Lagergren first order rate equation and Freundlich isotherm model. Desorption results indicated that around 60% to 80% of the adsorbed Hg(II) could be recovered from the carbons to 0.1 M HNO(3) solution by sonication treatment. Accordingly, it is believed that the activated carbons developed in this study are effective and practical for utilization in industrial wastewater treatment for mercury removal.

A novel functional material, Zeolite loaded ceramsite, was successfully developed from construction and demolition waste (CD (2) alkaline hydrothermal reaction for the synthesis of zeolite on ceramsite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to define the crystal structure and observe the morphology of the composite. Analysis results showed that multiplex porous structure was formed on the ceramsite due to the crystallization of the zeolites, which can largely improve the functional properties of the ceramsite, such as specific surface area, ion exchange capacity, adsorption capacity etc.

An activated carbon was developed from municipal sewage sludge (SS) using ZnCl2 as chemical activation reagent. Combined with TiO2, the carbon was tested for photocatalytic removal and recovery of ionic mercury [Hg(II)] in the form of metallic mercury [Hg(0)] from water. Hg(II) was first photoreduced to Hg(0) which was followed by adsorption on the SS carbon and TiO2 surfaces, then was recovered on a silver trap by means of heating. Combination of the SS carbon with TiO2 and under ultraviolet irradiation could doubled the adsorption capacity of mercury on the SS carbon, and the removal rate was increased to 151 g/kg compared to 87 g/kg for SS carbon only. The optimum amount of TiO2 for the photocatalytic reaction was 5–20% of the weight of SS carbon for photoreducing 10–80 mg/L of Hg(II) solutions. The optimum illumination time was 20 min and longer illumination could not enhance the photochemical reaction. Hg(II) removal from the solution increased with the increase of pH value, and reached a plateau value at the pH range of 5–12, and furthermore, the removal increased linearly with the increase of Hg(II) concentration. Introduction of methanol into the adsorption system could greatly enhance mercury adsorption capacity of the SS carbon, and the optimum methanol addition amount was found to be 5%, which doubled the adsorption capacity. The adsorption isotherm of mercury onto the SS carbon was found to follow Freundlich isotherm model perfectly. The recovery percentage of Hg(0) from water was around 40–65%. Accordingly, it is believed that the method developed in this study is effective and practical in industrial wastewater treatment for Hg(II) disposal.

This study was carried out to prepare low-cost adsorbents from different types of waste ashes and post-consumer PET for use in industrial wastewater treatment. PET was melted and blended with ashes. The mixture was then carbonized to form different types of adsorbents. Heavy metal leaching from the adsorbents was greatly reduced compared to leaching from the bulk ashes. The BET surface area of the adsorbents ranged from 115 to 485 m2/g. The acidic sites on the adsorbents varied from 0.84 to 1.56 meq./g, higher than that of the PET carbon. The adsorption of methylene blue (MB) or heavy metals on the adsorbents was not in accordance with their surface areas because acidic sites reaction, affinity adsorption and cation exchange all contribute to the adsorption of the adsorbents. The isotherm for MB adsorption on the adsorbents can be well described by the Langmuir or Freundlich equation but heavy metal adsorption cannot. It is believed that the adsorbents produced in this manner can be used in wastewater treatments for discoloration and heavy metal removal.

The present study was carried out to examine the contents of 18 minor and trace metals in five typical municipal waste ashes in Japan. In the waste ashes, Li, Ga, Rb, Y, Zr had relatively higher concentrations, approximately 5–300 mg kg−1, the remaining metal concentrations were generally approximately 0.05–20 mg kg−1. A comparison of the metal concentrations in the waste ashes and in Japanese agricultural soils indicated that the ratios for Ga, Mo, Ag, Sb, W, Bi between sewage sludge ash (SSA) and the soils were approximately 10–100 and for the remaining metals approximately 0.2–2; the ratios between food scrap ash (FSA), animal waste ash (AWA), horticulture waste ash (HWA) and incinerator bottom ash (IBA) and the soils were approximately 0.2–5. Furthermore, an overall evaluation on the waste ashes was also carried out using factor analysis with the addition of the other 21 elements examined in a companion paper. In the waste ashes, the major nutrient elements and heavy metals were mainly described by four factors: factors 1 and 2 explained the main information of the minor and trace metals while factors 3 and 4 explained that of the major nutrient elements. Factor 2 in the score plots could be used to evaluate the potential risk of the waste ashes to agricultural soils. Of the five types of waste ashes, SSA and IBA were abundant with minor and trace metals; AWA was relatively abundant with major nutrient elements especially for K; FSA was relatively abundant with major nutrient elements except for K, while HWA was not abundant with either of them.

This study was carried out to develop a cost-effective and practicable sorbent for application in abrupt perfluorooctane sulphonate (PFOS) pollution accidents. The main merit of this work was that a waste material, namely construction and demolition (C&D) waste, was employed as a raw base material for the sorbent synthesis. The waste material underwent alkaline fusion-hydrothermal synthesis and a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) modification process to form a CTAB-modified sorbent (CMCDSS). Experimental results showed that PFOS concentrations and solution pH had significant effect on the PFOS sorption on construction and demolition waste synthesized sorbent (CDSS) and CMCDSS (using 0.2CMCDSS as representative). PFOS could be effectively and rapidly adsorbed on CMCDSS, and sorption equilibrium was achieved within 2.5 h. The sorption amounts of PFOS on CMCDSSs enhanced along with the increase in CTAB loading amounts. Moreover, the CMCDSS can be applied effectively under acidic condition at pH 2-6 and various removal mechanisms were clarified at different sorption conditions. Accordingly, this work developed a novel and applicable material for dealing with abrupt environmental PFOS contamination accidents.

Incineration is one of the most important methods of municipal waste disposal. During incineration, various reactions of composition and decomposition may occur; the physical and chemical properties of municipal wastes may change to a great extent. In the present study, 15 samples, including food scraps (FS), animal wastes (AW) and sewage sludges (SS) were collected from various places in Japan, incineration treatments at 500 degrees C, 850 degrees C and 1000 degrees C were conducted in laboratory, and pH, EC, P content, various P forms, anions and soluble metals were determined. The results indicated that average pH increased by 1.09, 1.84, 2.27 and EC decreased by 4.6, 4.6, 5.6 ds m(-1) at 500 degrees C, 850 degrees C, 1000 degrees C, respectively, pH increased in the sequence of AMSSFS, and the decrease rate of EC was in the order of FSSSAM. Compared with no treatment (NT), water-soluble P decreased greatly at all three temperatures; available P increased at 500 degrees C, but decreased to the original level at 850 degrees C and 1000 degrees C; the amount of Ca-P, Fe-P and Al-P decreased and residual insoluble P increased greatly at 850 degrees C and 1000 degrees C; no significant change of total P was found at all three temperatures. However, water-soluble HPO4(2-) and Cl- decreased greatly, the decrease ratio of Cl- was in the sequence of SSFSAM at 500 degrees C, and FSSSAM at 850 degrees C and 1000 degrees C; no significant difference was found for HPO4(2-) among all three treatment temperatures; water-soluble SO4(2-) decreased at 1000 degrees C, but there was no significant change at 500 degrees C and 850 degrees C. Moreover, water-soluble Na, Mg, K, Ti, Mn, Fe, Ga, Cd, Zn, Ba, Pb, Sr, W and 0.1 M HNO3 soluble Al, K, Cr, Mn, Fe, Zn, Sr, Ba, Pb, Be, Ga, Rb, Cd, Sn, Sb, Ta, Tl, Bi, Na, Co, Ni, Sc, Cs decreased, but water-soluble Ca, Cr, Co, Ni and 0.1 M HNO3 soluble Cu, Ca, V, Mo, W, Th, U, Hf increased at 500 degrees C, 850 degrees C or 1000 degrees C.

A benign and effective process for cuprous chloride synthesis and simultaneously recovery of Ag and Pd from waste printed circuit boards (PCBs) was developed in the present study. The main merit of the process is that neither corrosive acid nor strong oxidant was used. The PCBs were firstly pretreated by thermal shock process to obtain metallic particles (MPs), then cuprous chloride was synthesized by reacting MPs with cupric sulfate in the presence of sodium chloride. The optimum V-NaCl/m(CuSO4) (mL/g) ratio, [Cu][Cu2+] mole ratio, treatment time and operation temperature were 6, 0.95, 30 min and 60 degrees C, respectively. Approximately 98.5% of Cu could be recovered from the PCBs through two synthesis circles. During the synthesis process, Ag and Pd could be simultaneously recovered by forming a stable chloride complex since Cu2+ played the role of oxidant in the system. The recovery percentages of Ag and Pd were 93.9% and 95.3%, respectively. Accordingly, it is believed that the process developed in the current study is benign and practical for copper and precious metal (Ag, Pd) recovery from waste PCBs. (C) 2013 Elsevier B.V. All rights reserved.

Waste printed circuit boards (PCBs) contain a large number of metals such as Cu, Sn, Pb, Cd, Cr, Zn, and Mn. In this work, an efficient and environmentally friendly process for metals recovery from waste PCBs by supercritical water (SCW) pre-treatment combined with acid leaching was developed. In the proposed process, waste PCBs were pre-treated by SCW, then the separated solid phase product with concentrated metals was subjected to an acid leaching process for metals recovery. The effect of SCW pre-treatment on the recovery of different metals from waste PCBs was investigated. Two methods of SCW pre-treatment were studied: supercritical water oxidation (SCWO) and supercritical water depolymerization (SCWD). Experimental results indicated that SCWO and SCWD pre-treatment had significant effect on the recovery of different metals. SCWO pre-treatment was highly efficient for enhancing the recovery of Cu and Pb, and the recovery efficiency increased significantly with increasing pre-treatment temperature. The recovery efficiency of Cu and Pb for SCWO pre-treatment at 420°C was 99.8% and 80%, respectively, whereas most of the Sn and Cr were immobilized in the residue. The recovery of all studied metals was enhanced by SCWD pre-treatment and increased along with pre-treatment temperature. Up to 90% of Sn, Zn, Cr, Cd, and Mn could be recovered for SCWD pre-treatment at 440°C.

Brominated flame retardants (BFRs) in electrical and electronic (E&E) waste plastic are toxic, bioaccumulative and recalcitrant. In the present study, tetrabromobisphenol A (TBBPA) contained in this type of plastic was tentatively subjected to solvothermal treatment so as to obtain bromine-free plastic. Methanol, ethanol and isopropanol were examined as solvents for solvothermal treatment and it was found that methanol was the optimal solvent for TBBPA removal. The optimum temperature, time and liquid to solid ratio for solvothermal treatment to remove TBBPA were 90 degrees C, 2 h and 15:1, respectively. After the treatment with various alcohol solvents, it was found that TBBPA was finally transferred into the solvents and bromine in the extract was debrominated catalyzed by metallic copper. Bisphenol A and cuprous bromide were the main products after debromination. The morphology and FTIR properties of the plastic were generally unchanged after the solvothermal treatment indicating that the structure of the plastic maintained after the process. This work provides a clean and applicable process for BFRs-containing plastic disposal. (C) 2012 Elsevier B.V. All rights reserved.

The degradation process of brominated flame retardant (BFR) and BFR-containing waste computer housing plastic in various supercritical fluids (water, methanol, isopropanol and acetone) was investigated. The results showed that the debromination and degradation efficiencies, final products were greatly affected by the solvent type. Among the four tested solvents, isopropanol was the most suitable solvent for the recovery of oil from BFR-containing plastic for its (1) excellent debromination effectiveness (debromination efficiency 95.7%), (2) high oil production (60.0%) and (3) mild temperature and pressure requirements. However, in this case, the removed bromine mostly existed in the oil. Introduction of KOH into the sc-isopropanol could capture almost all the inorganic bromine from the oil thus bromine-free oil could be obtained. Furthermore, KOH could enhance the depolymerization of the plastic. The obtained oil mainly consisted of single- and duplicate-ringed aromatic compounds in a carbon range of C9-C17, which had alkyl substituents or aliphatic bridges, such as butyl-benzene, (3-methylbutyl)-benzene, 1,1′-(1,3-propanediyl)bis benzene. Phenol, alkyl phenols and esters were the major oxygen-containing compounds in the oil. This study provides an efficient approach for debromination and simultaneous recovering valuable chemicals from BFR-containing plastic in e-waste.

Spent lithium-ion secondary battery (LIB) is one important kind of waste electric and electronic equipment (WEEE). At present, technologies available for spent LIBs recycling include chemical deposition, solvent extraction, Etoile-Rebatt process, electrodeposition, floatation and ion-exchanging. In this paper, a novel vacuum-aided pyro-metallurgical process for recovery metallic Co directly from waste LIBs was presented. The experiment results showed that 1) the decomposition and reduction rates of LiCoO2 increased with the increase of experiment temperature; and 2) metallic Co can be recovered successfully when the experiment temperature was higher than 700 C and the system pressure was maintained at 10 Pa. XRD and SEM results obtained at different temperatures showed that, in this paper, LiCoO2 was first reduced to CoO at a lower temperature and then it was reduced to metallic Co as the increase of temperature. This vacuum-aided pyrometallurgical process might be a promising one for spent LIBs recycling.

Waste cathode ray-tube (CRT) funnel glass is classified as hazardous waste since it contains high amount of lead. In the present study, a novel process for lead nanopowder synthesis from this type of glass was developed by combining vacuum carbon–thermal reduction and inert-gas consolidation procedures. The key trait of the process was to evaporate lead out of the glass to obtain harmless glass powder and synchronously produce lead nanoparticles. In the synthesis process, lead oxide in the funnel glass was firstly reduced to elemental lead, and evaporated rapidly in vacuum circumstance, then quenched and formed nano-size particles on the surface of the cooling device. Experimental results showed that temperature, pressure and argon gas flow rate were the major parameters controlling lead evaporation ratio and the morphology of lead nanoparticles. The maximum lead evaporation ratio was 96.8% and particles of 4–34 nm were successfully obtained by controlling the temperature, holding time, process pressure, argon gas flow rate at 1000 °C, 2–4 h, 500–2000 Pa, 50–200 ml/min, respectively. Toxicity characteristic leaching procedure (TCLP) results showed that lead leaching from the residue glass met the USEPA threshold. Accordingly, this study developed a practical and environmental-friendly process for detoxification and reclamation of waste lead-containing glass.

An interface-adaptive finite-element iteration scheme is designed to solve for the free interface of an inviscid steady-state density current. The method is also applied to free-surface flows over finite obstacles, but convergent solutions are obtained only for the supercritical flows. The success and failure of the method are discussed in association with the flow properties.

The recovery of valuable materials from waste printed circuit boards (PCBs) is quite difficult due to the heterogeneous mix of polymer materials, multiple kinds of metals and glass fiber. A feasibility study was conducted using supercritical methanol (SCM) to simultaneously recover polymers and metals from waste PCBs. The study focused on the characteristics of both oils and solid products obtained from the SCM-treated waste PCBs. The operation conditions were temperature range of 300-420 degrees C, treatment time between 30 and 120 min and solid-to-liquid ratio (S/L) of 1:10-1:30 (g/mL) so as to understand the products and depolymerization mechanisms of waste PCBs in SCM. GC-MS results revealed that the oils mainly contained phenol and its methylated derivatives, and the methylated derivatives increased with the increase of reaction temperature. The methylated reaction occurred mainly above 400 degrees C. The liquid products also contained a significant number of phosphated fire retardant additives such as triphenyl phosphate, which decreased significantly with the increase of reaction temperature. The solid product mainly consisted of Cu, Fe, Sn, Pb and Zn, as well as lower concentrations of precious metals such as Ag and Au.

The low-cost composite, nano-zerovalent iron (NZVI) contained in porous carbon (PC), was prepared using pinewood sawdust and ferric chloride as starting materials. The key point of this strategy was that the production of PC and the formation of NZVI were accomplished simultaneously through a simple process. The composite PC/NZVI was characterized by XRD, BET and the adsorption and simultaneous dechlorination of PCBs were efficiently demonstrated. The results showed the pinewood sawdust was activated by ferric chloride and the surface area and the pore volume of obtained composite were 423 m(2)/g and 0.23 cm(3)/g, respectively. The produced NZVI, around 27 nm in diameter, catalyzed the formation of substantial mesopores in the composite. PC/NZVI exhibited an efficient dechlorination of PCBs at room temperature, and the dechlorinated-products could be completely adsorbed onto the composite. Accordingly, it is believed that PC/NZVI developed in the present study is practically applicable for PCBs-contaminated water purification.

Hydrothermal conversion of biomass into biofuel could produce a special type of biochar as byproduct. This biochar is quite different from biochar derived from high temperature pyrolysis. In the present study, two biochars, prepared from hydrothermal liquefaction of pinewood (P300) and rice husk (R300), were characterized and investigated for lead removal from aqueous solution. The results indicated that the biochars contained a large amount of oxygen-containing groups on the surface, which were quite effective for lead removal with capacities of 4.25 and 2.40 mg/g for P300 and R300, respectively. The adsorption equilibrium was achieved around 5 h, Higher temperature favored the removal capacity implying that the adsorption was an endothermic process. The adsorption data at optimum solution pH 5 could be well described by Langmuir model and the adsorption process was well fitted by pseudo-second-order model. Moreover, it was found that the adsorption was mainly controlled by film diffusion. Thermodynamics analysis suggested that lead adsorption onto the biochars was physical endothermic process. (C) 2009 Elsevier B.V. All rights reserved