Treatment of textile wastewater by electrocoagulation using Al and Fe electrodes
Advancing the chemical engineering fundamentals
Electrochemical Engineering - II (T2-14b)
Keywords: Water treatment, Electrocoagulation, Textile industry, Heavy metals, sacrificial anodes
Textile wastewater is characterised by high levels of COD, suspended solids, heavy metals, dyestuffs and high turbidity. In particular, in their composition, the presence of heavy metals renders the use of biological treatment – the most commonly used technique – inappropriate for textile wastewaters.
Water treatment by electrocoagulation process uses metals sacrificial anodes: dissolved metal species destabilise and aggregates particles; in addition, they contribute to precipitate and adsorb dissolved contaminants. At the cathode, the evolved hydrogen bubbles entrap the large dispersed entities and ensure their flotation. The complexed particles are then removed by mechanical operation. Electrocoagulation has been considered for the treatment of a number of wastewaters, produced in various industrial branches: machining, chemical industry, productions of pharmaceutical substances, textile workshops, tannery, domestic wastes, agriculture sewages…In particular, electrocoagulation has been shown to be efficient for decolourisation of textile wastewaters, even though it is not certain that decolourisation means perfect treatment. In addition, the efficiency of the technique for the removal of heavy metals e.g. hexavalent chromium - has been little investigated.
The present paper deals with the treatment of textile wastewaters by electrocoagulation using either Al or Fe anodes inserted in an electrochemical cell –for production of the coagulant – installed in a flow rig operated batchwise. The treatment efficiency was followed by measurement of COD, turbidity, pH, heavy metal and dyestuff concentrations, depending on time, the current density and the initial concentration of the wastes and pH. Emphasis has also been put on the effect of the anode nature, for both the current efficiency of metal dissolution, and the rate of anode ageing in the process. The inhibition of the anode in long-term runs was also observed and compared, in view to designing pilot plant installations
The data obtained have been interpreted using a previously developed model for contaminant-metal hydroxide complexation and the values of the physicochemical parameters are discussed depending on the nature of the contaminant: dyestuff, dispersed matter and heavy metals. Also, the possible disposal of the solids recovered was also examined.
Presented Wednesday 19, 11:00 to 11:20, in session Electrochemical Engineering -II (T2-14b).
