Coagulation performance and floc characteristics of polytitanium tetrachloride and titanium tetrachloride compared with ferric chloride for coal mining wastewater treatment

Publication Type:
Journal Article
Separation and Purification Technology, 2015, 152 pp. 94 - 100
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© 2015 Elsevier B.V. Abstract The production and discharge of large volumes of wastewater during coal mining activities are one of the major environmental issues in Australia. Therefore, it is crucial to develop and optimise effective treatment processes for the safe disposal of coal mining wastewater (CMWW). In this study, we investigated the performance of a recently developed polytitanium tetrachloride (PTC) coagulant and compared with the performance of titanium tetrachloride (TiCl < inf > 4 < /inf > ) and the commonly used ferric chloride (FeCl < inf > 3 < /inf > ) coagulant for the treatment of CMWW from one of the coal mining sites in Australia. The use of Ti-based coagulants is particularly attractive for the CMWW treatment due to the advantage of being able to recycle the sludge to produce functional titanium dioxide (TiO < inf > 2 < /inf > ) photocatalyst; unlike the flocs formed using conventional coagulants, which need to be disposed in landfill sites. The results showed that both PTC and TiCl < inf > 4 < /inf > performed better than FeCl < inf > 3 < /inf > in terms of turbidity, UV < inf > 254 < /inf > and inorganic compounds (e.g. aluminium, copper or zinc) removal, howe ver, PTC performed poorly in terms of dissolved organic carbon removal (i.e. less than 10%). While charge neutralisation and bridging adsorption were the main coagulation mechanisms identified for TiCl < inf > 4 < /inf > treatment < inf > ; < /inf > sweep coagulation and bridging adsorption seemed to play a more important role for both PTC and FeCl < inf > 3 < /inf > treatments. The flocs formed by PTC coagulation achieved the largest floc size of around 900 μm with the highest floc growth rate. Both Ti-based coagulants (i.e., PTC and TiCl < inf > 4 < /inf > ) showed higher strength factor than FeCl < inf > 3 < /inf > , while TiCl < inf > 4 < /inf > coagulant yielded the flocs with the highest recovery factor. This study indicates that Ti-based coagulants are effective and promising coagulants for the treatment of CMWW.
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