Development and optimisation of treatment technologies for environmental pollution control
A number of sustainable and economically viable treatment methodologies have been developed and optimised to combat environmental pollution problems associated with the diversity and scattered nature of industries in Pakistan. The use of both electro-precipitation and electro-oxidation processes are shown to lead to the removal of dyes from textile effluent streams originating from various operations. The use of the electro-precipitation process, however, leads to a secondary disposal problem because sludge produced has to be disposed of safely. The use of an electrooxidation process does not produce sludge but is unable to remove some of the organic impurities from industrial textile effluent. Both processes do, however, result in colour removal from dye effluents with the degradation of dyes during electro-oxidation proceeding through the formation of different intermediate species before mineralization leading to complete mineralization in 30-40 minutes. Ames tests confirm that the treated effluent streams from both electro-precipitation and electro-oxidation processes are non-mutagenic. The electro-Precipitation process with mild steel anodes is also be used for the treatment of leather effluent streams to remove chromium by producing a mixed Cr(III) / Fe(III) hydroxide sludge. The same treatment process was successfully used for the simultaneous removal of dyes and chromium from mixed textile/leather effluent streams. The electro-precipitation process developed has been successfully tested on pilot scale at a textile mill in Faisalabad, Pakistan. A number of transition metal supported catalysts were shown to be ineffective in the oxidation of volatile organic compounds. For this reason a method of preparing platinum group metal catalysts on inert supports at low temperatures was developed and used to oxidise toluene, as an indicator of volatile organic compounds. The preferred catalyst support is y-A1203 which can be in the form of spheres or washcoated monoliths. In the case of y-A1203 spheres and the y-A1203 washcoated monolith complete oxidation of toluene was achieved at the relatively low temperatures of 236 and 2680C. A number of novel room temperature ionic liquids (RTILs) were synthesised, characterised and their potential application for selective extraction of copper from industrial wastes is also reported. The solubility studies of different metal oxides in the RTIL, 1-(2-cyanoethyl)-3-methylimidazolium bromide, show that it can be used for the selective extraction of copper from industrial waste samples containing other metal oxides. This RTIL has the ability to selectively dissolve, copper, copper oxide and copper sulfide when the reaction is carried out in the presence of water.