The use of carbon nanotubes and siliconcarbide (unique forms of amorphousmaterials) for the extraction of cr(vi) from a chemical matrix

This chapter focuses mainly on an application of two types of amorphous materials,namely carbon nanotubes and silicon carbide to extract Cr(VI) from industrial waste.However, the properties of these materials are first discussed. The detailed study wasconducted as a function of chemical composition, contact time and other matrix orimpurity effects. Studies were also conducted by embedding the MWCNTs into anotheramorphous material namely silicon carbide nanopowder. These studies included controlexperiments in which the MWCNTs and silicon carbide was used as the sole adsorbent.Synthesized MWCNTs which contained no functional groups showed a higher adsorptioncapacity for Cr(VI) but the maximum percentage uptake was highly dependent on thechemical composition of the industrial effluent. The highest adsorption of Cr(VI) in thestudy was observed when the synthesised MWCNTs were embedded into a siliconcarbide matrix and when these MWCNTs were used as the sole adsorbents. Desorptionexperiments (achieved by using NaOH as the washing agent) were also conducted andshowed that Cr(VI) can be reversibly desorbed (almost 100%) even after six adsorptiondesorptioncycles. Thus, adsorption of Cr(VI) by MWCNTs can be considered as aneffective treatment technology for the remediation of Cr(VI) provided that all chemical interferences are eliminated prior to treatment,