A review on demineralization, activation, and potential applications of the solid fraction obtained from the pyrolyzed waste tires

Abstract

The abundant disposal of waste tires which are usually abandoned in landfills and left untreated, has raised global concerns. In mitigating this major issue, pyrolysis is a promising thermochemical process that converts waste tires into three main products that could be further valorized to be applied in various applications. Raw recovered carbon black (rCB), the solid carbonaceous matrix, is one of the products obtained from the pyrolysis of waste tires. This raw rCB is further processed, milled and pelletized to produce rCB. rCB is seen as a potential material as an alternative substitute for virgin carbon black, vCB. However, the poor quality of rCB limits its utilization of rCB, which calls for the need for treatment and modification. Systematic analysis of demineralization and activation of rCB is urgently needed for economic and commercial feasibility. Thus, this review analyzed the effect of demineralization and activation on the properties of rCB. Parameters such as concentration, and the type of acid and base used during demineralization were examined. The comparison of different activating agents and other parameters, such as temperature and impregnation ratio during physical and chemical activation was discussed in detail. Based on the presented data, the optimal conditions (i.e., temperature, duration, and impregnation ratio) are important to avoid unnecessary production costs (i.e., excessive chemicals used, or energy wasted). This review also aims to provide a selection of suitable demineralization and activation methods for generating a multifunctional carbon material with the desired properties. Hence, the development of carbon-based materials derived from waste tires which can partially or completely replace vCB, offers economic viability, versatility, sustainability, and safeguarding towards the environment and human health.