Date of Award

31-8-2024

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.R.S.Saravanan

Second Advisor

Dr.V.Ponnusami

Keywords

Biochar, Pyrolysis, Waste Valorization, Chemical Activation, Activated Carbon

Abstract

Pyrolysis is a thermochemical conversion method to produce gas and liquid fuels from lignocellulosic biomass. This process involves the thermal decomposition of organic compounds without oxygen. The vapors formed are rapidly condensed to yield a liquid product called bio-oil and a solid product called biochar.

In the present study, Sesame indicum (SI) (herbaceous agro residue) and Prosopis julifora (PJ) (woody biomass weed) were chosen as feedstocks for the pyrolysis process and the respective solid and liquid products were collected and characterized. The proportion of biomass pyrolysis products is significantly influenced by biomass composition and process conditions such as temperature, heating rate, and residence time. The kinetic models for the thermal decomposition of SI and PJ biomass were calculated using the isoconversional models, and energy and exergy analysis was performed.

A comparison between these systems, such as thermal decomposition characteristics and kinetic behavior, could help identify the ideal operating conditions for both energy and environmental applications. Biochar obtained from PJ exhibits a highly porous morphology with a wide range of surface area.

Moreover, the surface chemistry of biochar can be altered by introducing several chemical functional groups using physical and chemical activations. We have investigated the effect of physical and various chemical activations of PJ biochar, which can be exploited for energy and environmental applications. The zinc chloride (ZnCl2) activated biochar was utilized for the adsorptive removal of ciprofloxacin, an emerging contaminant in batch and continuous mode.

Activated carbon prepared using treatment with potassium hydroxide (KOH) from PJ Biochar is utilized for supercapacitor electrodes and has high specific capacitance and excellent performance. On the other hand, SI pyrolysis produced bio-oil with a high amount of water content. The bio-oil aqueous phase (BOAP) obtained from SI pyrolysis showed that it could be a promising candidate for fighting hospital-associated infections (HAIs).

Techno-economic and comparative life cycle assessment shows that the activated PJ biochar is a sustainable alternative to fossil fuel-derived activated carbons. Based on the results obtained from this study, both PJ and SI biomass could be efficiently utilized for both energy and environmental applications, which will be otherwise regarded as waste.

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