**Abstract**

The development of better and efficient methods of consuming less and/or wasting little resource materials is becoming more important. In this study, pyrolytic waste tyre carbon black residue and commercial grade activated carbon were characterized and evaluated against adsorption of mercury vapor. The performance of the raw carbon black residue and the activated carbon against mercury vapor generated in the laboratory was determined using a designed reactor system. The adsorption of Hg+ was investigated at temperatures ranging from 200 to 280°C for 6 hours. Batch experiments were conducted for the different carbon residue samples and characterization analysis were done before and after adsorption using the spectroscopic, microscopic, and structural techniques to elucidate the structural arrangements and properties of the carbonaceous materials. Spectroscopic analysis of these carbonaceous residues showed a C=C stretching vibration attributed to the lignocellulose aromatic ring at 1657–2000 cm−1. Comparatively, it was also observed that the Infrared spectrum of raw carbon black exhibits less functional groups as compared to the H2SO4-AC and H2O2-AC carbonaceous residues prepared.

**Keywords:** Tyre waste, pyrolysis, activated carbon, mercury vapor, adsorption

## **1. Introduction**

The continually growing global economies inevitably results in a steady increase of the automobile industry, which unavoidably produces huge amounts of end-oflife waste tyres. It is estimated that about 1.5 billion waste tyres are produced annually worldwide [1]. In South Africa, the majority of these waste tyres are landfilled and do not readily decompose, contributing to both land and air pollution [2]. The carbon black currently produced via pyrolysis has not been put to any significant use as to justify its economic/environmental production from the plant operations. On the hand, mercury (Hg) is a known neurotoxin and can be dangerous once it is released into the environment [3]. It is a toxic heavy metal that bio accumulates in organisms and causes brain and liver damage if digested or inhaled by human beings. The efficiency and sustainability of control and management of mercury vapor release from compact flourescent lamp waste in South Africa, however is not adequately documented and therefore specific studies aimed at developing cheaper and locally available technology to control this are necessary.

The phenomenon of mercury, (Hg vapor) Hg-vapor sorption is well recognized and accepted. However, vapor sorption of many vapors is a well-recognized physical principle. Gaseous materials such as Hg vapor diffuse into a solid host material

because of differences in concentration. This driving force for adsorption continues until equilibrium conditions are established between the vapor phase and the solid phase. The solubility of one material in another is generally governed by the rule "like dissolves like." Mercury vapor exists as a nonpolar molecule that would likely be most soluble in nonpolar substances such as other metals and nonpolar hydrocarbons [4]. At first glance the new energy efficient lighting technology appears to be the better way to reduce energy consumption and protecting the environment. However, the serious mercury management concerns associated with use of CFL lamps needs to be considered and addressed. Depending on the type of lamp, a longitudinal compact fluorescent lamp may contain mercury from greater than 0.1 up to 100 milligrams (mg). Although cleaning and recovery methods have been developed and are implementation stages, efficient levels of the containment of the released mercury vapor during the recycling processes are not clearly known. Therefore there is a need for the development of a cheaper and locally available mercury recovery adsorbent material from waste tyres pyrolytic carbonaceous residues for use at recycling facilities in South Africa. This study therefore seeks to investigate the use of carbon black residue from waste tyre pyrolysis as an adsorption agent for the removal of mercury vapor from fluorescent lamp waste recycling, yet another waste hurdle, the country is grappling on.
