Synthesis of carbon-natural zeolite composites with controlled amount of carbon and evaluation of their adsorption properties
Natural zeolite is well known for the removal of heavy metals and has a wide spread application, but it shows negligible adsorption for organics. The objective of this research was to enhance the adsorption capacity of natural zeolite. A composite of carbon and natural zeolite is synthesised as a prospective adsorbents for organics. The composite was prepared by saturating the natural zeolite with carbon precursor (Furfural alcohol), and then carbonised at 800 oC in inert atmosphere for 6-8 hours. The amount of carbon content of the composite was fixed by controlling the amount of precursor used in the synthesis. Several composites were synthesized having different amount of carbon. The sample were characterised by different techniques such as SEM, TEM, FTIR, FTRAMAN, XRD etc. The composites had carbon content from 0.5 to 3% by weight. The disorganised arrangement of carbon aromatic sheets in the composite provides a partial negative charge on the adsorbent which helps in enhancing the organic adsorption capacity. This indicates that composite having larger amount of carbon will have higher adsorption capacity. Phenol adsorption isotherm indicates the enhanced adsorption of composite as compared to natural zeolite. It also shows that the adsorption increases with increase in the carbon content of the composite. The equilibrium data were tested with Langmuir, Freundlich, Tempkin and Smith model. Langmuir and Tempkin model gave a good fit of the experimental data. The maximum adsorption capacity was found close to 18 mg/g for composite with highest carbon content.