Demonstration of the efficiency and robustness of an acid leaching process to remove metals from various CCA-treated wood samples.

In recent years, an efficient and economically attractive leaching process has been developed to remove metals from copper-based treated wood wastes. This study explored the applicability of this leaching process using chromated copper arsenate (CCA) treated wood samples with different initial metal loading and elapsed time between wood preservation treatment and remediation. The sulfuric acid leaching process resulted in the solubilization of more than 87% of the As, 70% of the Cr, and 76% of the Cu from CCA-chips and in the solubilization of more than 96% of the As, 78% of the Cr and 91% of the Cu from CCA-sawdust. The results showed that the performance of this leaching process might be influenced by the initial metal loading of the treated wood wastes and the elapsed time between preservation treatment and remediation. The effluents generated during the leaching steps were treated by precipitation-coagulation to satisfy the regulations for effluent discharge in municipal sewers. Precipitation using ferric chloride and sodium hydroxide was highly efficient, removing more than 99% of the As, Cr, and Cu. It appears that this leaching process can be successfully applied to remove metals from different CCA-treated wood samples and then from the effluents.

Counter-current acid leaching process for copper azole treated wood waste.

This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H2SO4 at 75degrees C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving > or = 94% copper extraction from the wood during the 10 cycles; 80-90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

Semi-passive in-situ pilot scale bioreactor successfully removed sulfate and metals from mine impacted water under subarctic climatic conditions.

Mine drainage contaminated with metals is a major environmental threat since it is a source of water pollution with devastating effects on aquatic ecosystems. Conventional active treatment technologies are prohibitively expensive and so there is increasing demand to develop reliable, cost-effective and sustainable passive or semi-passive treatment. These are promising alternatives since they leverage the metabolism of microorganisms native to the disturbed site at in situ or close to in situ conditions. Since this is a biological approach, it is not clear if semi-passive treatment would be effective in remote locations with extremely cold weather such as at mines in the subarctic. In this study we tested the hypothesis that sulfate-reducing bacteria, which are microorganisms that promote metal precipitation, exist in subarctic mine environments and their activity can be stimulated by adding a readily available carbon source. An experiment was setup at a closed mine in the Yukon Territory, Canada, where leaching of Zn and Cd occurs. To test if semi-passive treatment could precipitate these metals and prevent further leaching from waste rock, molasses as a carbon source was added to anaerobic bioreactors mimicking the belowground in-situ conditions. Microbial community analysis confirmed that sulfate-reducing bacteria became enriched in the bioreactors upon addition of molasses. The population composition remained fairly stable over the 14 month operating period despite temperature shifts from 17 to 5 °C. Sulfate reduction functionality was confirmed by quantification of the gene for dissimilatory sulfite reductase. Metals were removed from underground mine drainage fed into the bioreactors with Zn removal efficiency varying between 20.9% in winter and 89.3% in summer, and Cd removal efficiency between 39% in winter and 90.5% in summer. This study demonstrated that stimulation of native SRB in MIW was possible and that in situ semi-passive treatment can be effective in removing metals despite the cold climate.

Pilot-scale investigation of the robustness and efficiency of a copper-based treated wood wastes recycling process.

The disposal of metal-bearing treated wood wastes is becoming an environmental challenge. An efficient recycling process based on sulfuric acid leaching has been developed to remove metals from copper-based treated wood chips (07.3 kgm(-3)) and more than 94.5% of Cu was removed from ACQ-, CA- and MCQ-treated wood. The treatment of effluents by precipitation-coagulation was highly efficient; allowing removals more than 93% for the As, Cr, and Cu contained in the effluent. The economic analysis included operating costs, indirect costs and revenues related to remediated wood sales. The economic analysis concluded that CCA-treated wood wastes remediation can lead to a benefit of 53.7 US$t(-1) or a cost of 35.5 US$t(-1) and that ACQ-, CA- and MCQ-treated wood wastes recycling led to benefits ranging from 9.3 to 21.2 US$t(-1).

Application of a CCA-treated wood waste decontamination process to other copper-based preservative-treated wood after disposal.

Chromated copper arsenate (CCA)-treated wood was widely used until 2004 for residential and industrial applications. Since 2004, CCA was replaced by alternative copper preservatives such as alkaline copper quaternary (ACQ), copper azole (CA) and micronized copper quaternary (MCQ), for residential applications due to health concerns. Treated wood waste disposal is becoming an issue. Previous studies identified a chemical process for decontaminating CCA-treated wood waste based on sulfuric acid leaching. The potential application of this process to wood treated with the copper-based preservatives (alkaline copper quaternary (ACQ), copper azole (CA) and micronized copper quaternary (MCQ)) is investigated here. Three consecutive leaching steps with 0.1 M sulfuric acid at 75°C for 2 h were successful for all the types of treated wood and achieved more than 98% copper solubilisation. The different acidic leachates produced were successively treated by coagulation using ferric chloride and precipitation (pH=7) using sodium hydroxide. Between 94 and 99% of copper in leachates could be recovered by electrodeposition after 90 min using 2 A electrical current. Thus, the process previously developed for CCA-treated wood waste decontamination could be efficiently applied for CA-, ACQ- or MCQ-treated wood.

Optimization of a chemical leaching process for decontamination of CCA-treated wood.

Increasing volumes of discarded Chromated Copper Arsenate (CCA)-treated wood require the development of new treatment and recycling options to avoid the accumulation of wood wastes in landfill sites, resulting in dispersion of contaminants in the environment. The aim of this study is to design an economic chemical leaching process for the extraction of arsenic, chromium and copper from CCA-treated wood. Choice of chemical reagent, reagent concentration, solid-to-liquid ratio, temperature, reaction time and wood particle size are parameters which have been optimized. Sulphuric acid was found to be the cheapest and most effective reagent. Optimum operation conditions are 75 degrees C with 0.2N H(2)SO(4) and 150 g wood L(-1). Under these conditions, three leaching steps lasting 2h each allowed for 99% extraction of arsenic and copper, and 91% extraction of chromium. Furthermore, arsenic concentration in TCLP leachate is reduced by 86% so the environmental hazard is reduced. Decontamination process cost is estimated to 115US$ per ton of treated wood. These results demonstrate the feasibility of chemical remediation and that sulphuric acid leaching is a promising option for CCA-treated wood waste management.

Selective recovery of Cr and Cu in leachate from chromated copper arsenate treated wood using chelating and acidic ion exchange resins.

The purpose of this study was to selectively remove chromium and copper from CCA-treated wood acid leachates (initial concentrations of 447-651 mg As l(-1), 374-453 mg Cu l(-1) and 335-622 mg Cr l(-1)) using ion exchange resins and precipitation techniques. Batch experiments revealed that the chelating resin Dowex M4195 had a high copper selectivity in the presence of chromium while the Amberlite IR120 resin had a high chromium sorption capacity. Combining M4195 and IR120 resins in four successive columns, made with Plexiglas tube, led to 96% copper extraction and 68% chromium extraction. NH(4)OH (4M) efficiently eluted copper from the chelating resin while H(2)SO(4) (10%v/v) was used for IR120 resin elution. Copper and chromium recovery by elution reached 94% and 81%, respectively. Successive sorption and elution steps using M4195 and IR120 ion exchange resins presented similar metal removal capacities over the five cycles. No resin deterioration was observed but the results suggested arsenic bulk diffusion into the M4195 resin. Successive treatments of CCA-treated wood leachate with M4195 and IR120 allowed for copper and chromium removal while arsenic could be extracted by coagulation treatment with ferric chloride and precipitation with Ca(OH)(2) at pH 5.7. This final process led to 99.9% arsenic removal. The final effluent contained less than 1 mg l(-1) of arsenic, chromium and copper.

Methotrexate as an alternative therapy for chronic calcium pyrophosphate deposition disease: an exploratory analysis.

OBJECTIVE: To evaluate the effectiveness of methotrexate (MTX), which works not only as an immunosuppressant, but also as a potent antiinflammatory agent, as an alternative therapeutic option for patients with severe calcium pyrophosphate deposition disease (CPDD) who fail to respond to standard therapy with nonsteroidal antiinflammatory drugs and/or glucocorticoids. METHODS: We analyzed, in 2 university hospitals in Switzerland, consecutive patients with CPDD that was resistant to classic treatment and were subsequently treated with MTX. Before and after initiation of MTX therapy, we quantified the frequency of pseudogout attacks, pain intensity, the number of swollen and tender joints, and inflammatory biomarkers. Clinical and biologic side effects of MTX and patients satisfaction with MTX treatment were also evaluated. RESULTS: The study included 5 patients treated with low dosages of MTX (5-20 mg/week). The mean followup time with MTX was 50.4 months (range 6-81 months). All patients reported an excellent clinical response, with marked improvement within a mean period of 7.4 weeks. A significant decrease in pain intensity (P < 0.0001), swollen and tender joint counts (P < 0.0001), and frequency of attacks was observed. The biomarkers of inflammation decreased markedly when systematically analyzed (3 patients). No significant side effects were reported. CONCLUSION: This study suggests that MTX could be a valuable therapeutic option for severe CPDD that is refractory to conventional therapy.