Life savers from waste
By PTA News Bureau
Extracting high-quality activated carbon from waste tyre is a lengthy process, but the techniques developed by Dr Vinod Kumar Gupta, eminent researcher in environmental chemistry and chemical sensors and former Professor of Chemistry, at the Indian Institute of Technology, Roorkee, have proved cost-effective. What is more the eco- friendly process has resulted in producing activated carbon that is suitable for water treatment and in the manufacture of life-saving medicines.
There are two processes that Dr Gupta, a former Vice Chancellor of Dr R ML Avadh University Faizabad in the north Indian state of Uttar Pradesh, have developed to produce activated carbon from waste tyres. One is the rubber tyre activated carbon modification (RTACMC) and the other, the rubber tyre activated carbon (RTAC).
In the RTAC process, the ground tyre granules are cleaned and washed with deionised water, and then dried in an oven at 100˚C for two hours. This dried material is then heated to 500˚C for five hours for carbonization. This is followed by treatment with hydrogen peroxide solution for 24 hours at 60˚C to oxidize adhering organic impurities. The material is again washed with deionised water three times to remove hydrogen peroxide and dried at 110º C for two hours in vacuum oven.
The dried material is activated to 900˚C for two hours in a covered silica crucible by heating in a muffle furnace. The crucible is removed from the furnace and cooled in a desiccator. The material is then treated with hydrochloric acid solution to remove the ash content and then washed with deionised water. This is followed by drying of the material at 100˚C for 24 hours.
The dried product of particle size 150-200 μm is referred to as RTAC and stored in separate vacuum desiccators until required, said Dr Gupta, who was a Visiting Professor (DAAD) at the Technical University of Chemnitz and Freie University of Berlin and KFUPM Chair Professor at King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. He has undertaken many sponsored research and consultancy projects in India and abroad.
Dr Gupta said that in the case of RTACMC, the char is obtained after carbonization in the same way as in the case of RTCA. It is then mixed with potassium hydroxide (KOH) pellets with KOH/char impregnation ratio of 1.5. The impregnation ratio = weight (KOH) (g)/weight (char) (g)
The activation step is performed in a glass reactor placed inside a microwave oven with input power set at 600 W and an irradiation time of 10 minutes to produce RTACMC. This sample is washed with deionised water until the pH of the solution becomes neutral and stored for further characterization and adsorption tests.
Explaining the advantages and disadvantages of both microwave-assisted chemical treatment and physical heating, Dr Gupta said that microwave heating is found to be more cost-effective. “The advantage associated with using microwave heating is that the treatment time and consumption of gases can be considerably reduced, which further results in the reduction of energy consumption as well,” he said.
(Full Text in PTA April-May issue)