Abstract

Reducing sewage sludge (SS) waste has been a substantial challenge in urban areas. Utilization of SS with organic-rich residue as a renewable resource for conversion to value-added products is an alternative solution. It can manage the continuously increasing SS generation while is an appealing pathway for energy sustainability and environmental protection. In this respect, pyrolysis is a promising technology for the thermochemical valorization of SS to useful products, including char, bio-oil and bio-gas with different applications. Accordingly, in the present research, the thermal behaviors, kinetics and thermodynamics of SS and low-density polyethylene (LDPE) during co-pyrolysis were studied through thermogravimetric analysis. Discrepancies between theoretical and experimental weight loss curves as a measurement of the extent of synergic effect proved the existence of chemical interactions during the process. Meanwhile, kinetic and thermodynamic parameters provided vital information on the degradation behavior of the reactants. Furthermore, this work focused on extending the application of activated char (AC) derived from pyrolysis of SS. In this context, a fixed bed pyrolysis reactor system was designed and implemented. Firstly, the produced AC was used as an alternative catalyst to HZSM5 in catalytic pyrolysis of SS. As a result, both catalysts promoted SS pyrolysis reaction rate by abridging the average activation energy. Interestingly, the catalysts effectively reduced the harmful evolved gaseous generated during the process (eg., CH4, CO2, HCN, NO2, SO2 and CH3SH). Moreover, the bio-oil composition analysis showed a major upgrade in terms of oxygen-nitrogen-containing compounds removal. Upgraded bio-oil was dominated by C4-C9 hydrocarbons (72%) at higher catalyst loadings. Also, generation of value-added chemicals such as light aromatic hydrocarbons was enriched in the catalytic process. Secondly, the application of sludge-based AC, as a sorbent, for the recovery of oil spills on surface waters was invested. The inherent Fe-minerals in SS texture were converted to magnetic Fe3O4 particles during the pyrolysis reaction allowing the exhausted sorbent to be recovered with a magnetic field. Concurrently, superhydrophobic property was created by modification of AC with myristic acid, resulting in a water contact angle of 152.2°. Feasibility studies proved the potential use of sludge-based sorbent for oil spill response operations.