Adsorption of contaminants onto a char obtained by pyrolysis of used tyres and rubber wastes: a possible low-cost alternative in the groundwater remediation technologies

Soil and groundwater contaminations by mixture of compounds seems to be very diffused. The watchword in the decision of the remediation technology for each scenario is to select the most sustainable option, among the possible alternatives (Jia et al., 2017). Conventional strategies for DNAPLs, VOCs compounds or heavy metals removal provides the use of sorbent materials, but what makes the adsorption technology feasible is the high performance at low concentration revealed in the aquifer and the low cost of the material. Carbonaceous materials are the most used sorbent for this kind of application and Activated Carbon (AC) is usually the sorbent with the highest performances achieved. In recent years the scientific community has focused on the search of new low-cost materials such as biochars obtained from thermal conversion of agricultural wastes and biomass, or the carbon black from waste tyres pyrolysis. The disposal of waste tyres represents a serious problem indeed, hence the pyrolysis of pneumatic tyres and rubbers is advantageous due to their high calorific value and because of the products generated: the oil can be used as fuel, the gases for heating, while the solid waste is studied for gasification, combustion and for activated carbon preparation. In this study we are investigating a carbon black obtained in a pyrolysis plant working in Krasnodar (RU): the feedstock for pyrolysis is composed by used tyres of cars and various waste products of rubber goods, like hoses, high-pressure hoses, drive belts of agricultural machinery and conveyor belts; the temperature setting is 350°C. The char is characterized by preliminary chemical composition analysis, SEM and X-ray analysis, meso-, micro-pores and surface area (BET) analysis. Secondly adsorption tests are realized on the raw material: contaminated solutions with Toluene, Trichloroethylene and Lead (Pb2+) were put in contact with different amount of material, therefore kinetic and equilibrium tests in batch reactors are performed. Experimental data of isotherm curves are fitted with Langmuir and Freundlich model and compared with commercial activated carbon and biochars performances. Results are interesting considering that the material is used without preceding modification or activation, but further investigations are needed. A fixed-bed reactor in a plexiglass column filled with sand and reactive material is ongoing in order to draw the breakthrough curve and evaluate the material’s performance in continuous conditions.