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Lead II chloride solutions containing 10, 100 and 1 000 ppm Pb were decontaminated with chemically treated bark. The percentage of Pb cations removed from solution was found to depend on pH and initial concentration: about 99% of the initial Pb content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1 000 ppm respectively. The maximum retention capacity of the treated bark was about 83 mg Pb/g modified bark. Infra-red spectroscopy of loaded bark suggested that the Pb reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the release of two H+ ions when a Pb cation is removed by the bark seems to indicate ion exchange with hydrogen from the hydroxyl groups., Lead II chloride solutions containing 10, 100 and 1 000 ppm Pb were decontaminated with chemically treated bark. The percentage of Pb cations removed from solution was found to depend on pH and initial concentration: about 99% of the initial Pb content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1 000 ppm respectively. The maximum retention capacity of the treated bark was about 83 mg Pb/g modified bark. Infra-red spectroscopy of loaded bark suggested that the Pb reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the release of two H+ ions when a Pb cation is removed by the bark seems to indicate ion exchange with hydrogen from the hydroxyl groups.

The efficiency of modified bark in removing Cd cations from effluents after conventional neutralisation and precipitation was tested. About 99.9% of Cd was removed from synthetic solutions containing 10 ppm, 99% from solutions with 100 ppm and 96% from solutions with 1 000 ppm. Pilot plant trials using an industrial effluent containing about 0.5 ppm led to almost complete elimination., The efficiency of modified bark in removing Cd cations from effluents after conventional neutralisation and precipitation was tested. About 99.9% of Cd was removed from synthetic solutions containing 10 ppm, 99% from solutions with 100 ppm and 96% from solutions with 1 000 ppm. Pilot plant trials using an industrial effluent containing about 0.5 ppm led to almost complete elimination.

Chemically treated bark of pedunculate oak, Scots pine, European beech and European spruce was used to decontaminate copper acetate, chloride, nitrate and sulphate containing 10, 100 and 1 000 ppm Cu. The percentage of metal removed varied from 40% to 99%, depending on pH and initial concentration, and to some extent on the salt used. The maximum retention capacity of the treated bark varied from 31 to 43 mg Cu/g dry bark. Loaded bark was analysed by SEM and IR spectroscopy: Cu was uniformly distributed with no observed segregation, and appeared to be bound to the acidic sites of the bark. No anions were detected by either technique., Chemically treated bark of pedunculate oak, Scots pine, European beech and European spruce was used to decontaminate copper acetate, chloride, nitrate and sulphate containing 10, 100 and 1 000 ppm Cu. The percentage of metal removed varied from 40% to 99%, depending on pH and initial concentration, and to some extent on the salt used. The maximum retention capacity of the treated bark varied from 31 to 43 mg Cu/g dry bark. Loaded bark was analysed by SEM and IR spectroscopy: Cu was uniformly distributed with no observed segregation, and appeared to be bound to the acidic sites of the bark. No anions were detected by either technique.

Laboratory studies have been undertaken of the use of agricultural and food processing by-products to decontaminate synthetic solutions, urban water and industrial effluents. The separation of pollutants depended on the type of organic substrate used, initial concentration and nature of pollutants and pH. It was found possible to recover 20-99% of pollutants present in solution in less than 30 mins. The retention capacity of organic substrates varied from 0.12 to 4.36 mole/kg of dry substrate. The interaction between the organic substrate and the metal ions was mainly controlled by an ion exchange mechanism. The processes could be used before or after conventional effluent treatment technology. In some cases, incineration or pyrolysis of the saturated substrate generated residues rich enough to be recycled in secondary metal production units. The energy consumption of the proposed process is about 0.3 kWh/m3. Capital and operating costs are low as the process flowsheet is simple., Laboratory studies have been undertaken of the use of agricultural and food processing by-products to decontaminate synthetic solutions, urban water and industrial effluents. The separation of pollutants depended on the type of organic substrate used, initial concentration and nature of pollutants and pH. It was found possible to recover 20-99% of pollutants present in solution in less than 30 mins. The retention capacity of organic substrates varied from 0.12 to 4.36 mole/kg of dry substrate. The interaction between the organic substrate and the metal ions was mainly controlled by an ion exchange mechanism. The processes could be used before or after conventional effluent treatment technology. In some cases, incineration or pyrolysis of the saturated substrate generated residues rich enough to be recycled in secondary metal production units. The energy consumption of the proposed process is about 0.3 kWh/m3. Capital and operating costs are low as the process flowsheet is simple.

Laboratory scale studies have been carried out of the decontamination of synthetic K2Cr2O7 solutions containing 10-1 000 ppm hexavalent chromium using chemically treated barks. A 2% pulp density in an agitated flask at optimum pH for two hours resulted in 95% chromium removal. Column percolation trials established the maximum retention times of the treated bark. Oak and pine bark had saturation rates of 110 and 215 mg Cr/g bark, respectively and incineration of the metal charged barks produced recyclable ashes containing 36 and 54% of Cr metal. Semi-pilot plant scale studies were carried out on Cr6+ removal from industrial effluents containing up to 1 800 ppm and about 90% of the Cr6+ was eliminated., Laboratory scale studies have been carried out of the decontamination of synthetic K2Cr2O7 solutions containing 10-1 000 ppm hexavalent chromium using chemically treated barks. A 2% pulp density in an agitated flask at optimum pH for two hours resulted in 95% chromium removal. Column percolation trials established the maximum retention times of the treated bark. Oak and pine bark had saturation rates of 110 and 215 mg Cr/g bark, respectively and incineration of the metal charged barks produced recyclable ashes containing 36 and 54% of Cr metal. Semi-pilot plant scale studies were carried out on Cr6+ removal from industrial effluents containing up to 1 800 ppm and about 90% of the Cr6+ was eliminated.

Preliminary results are presented of a low cost process dedicated to the decontamination of industrial effluents by chemically treated barks. Studies using solutions containing hexavalent chromium showed that the metal removal percentage depends on pH, initial concentrations and the tree species. More than 95% of Cr6+ contained in a 10, 100 or 1 000 ppm solution can be recovered at pH 3.80. The ashes obtained by the incineration of the saturated bark contain up to 50% of chromium metal which can be recycled by traditional metallurgical processes. Pilot plant trials were successful in eliminating about 90% of Cr6+ from industrial effluents containing about 5 000 ppm., Preliminary results are presented of a low cost process dedicated to the decontamination of industrial effluents by chemically treated barks. Studies using solutions containing hexavalent chromium showed that the metal removal percentage depends on pH, initial concentrations and the tree species. More than 95% of Cr6+ contained in a 10, 100 or 1 000 ppm solution can be recovered at pH 3.80. The ashes obtained by the incineration of the saturated bark contain up to 50% of chromium metal which can be recycled by traditional metallurgical processes. Pilot plant trials were successful in eliminating about 90% of Cr6+ from industrial effluents containing about 5 000 ppm.