Chromium contamination in the Glasgow environment and the potential for remediation
This project investigated the traditional treatment of chromium by oxidation-reduction reaction using Fe (II) and Mn (II). It was found that FE (II) was a potential remediation to stabilise chromium and reduce Cr (VI) to Cr (III), but Mn (II) oxidised Cr (III) to Cr (VI) mobilising it to the leachate. The characteristic of chromium leaching from soil was studied and showed there was fast release followed by a slow release. After a dry period the initial leachate had a high chromium concentration, this points out that the leaching of chromium is a long-term process. Those aspects of fast and slow release and the high chromium concentration at the initial pulse have been a concern for designing a system of fixed bed, low cost material such as (charcoal, coir, peat and wood bark) for adsorbing chromium from the leachate. The adsorption – desorption properties were studied, as both are of equal concern, and the Langmuir equation was applied for the various sorbent materials. Charcoal had a high percentage of Cr (VI) adsorbed, but on the other hand also had a high percentage of Cr (VI) desorbed. When applied to the column leach charcoal could not adsorb Cr (VI) properly. Wood bark had the lowest percentage of chromium released to the solution; therefore it was selected for further studies. The wood bark was studied with different contact times by both batch and flow through systems. The results showed that more chromium was adsorbed with longer contact time. The system using 2500g of wood bard completely retained chromium from a solution of about 100 litres of 30 mg Cr/l with a flow rate of 60 ml/h. The experimental results can be applied to larger scale systems; however, the system needs further development.