Micro- and mesoporous-enriched carbon materials prepared from a mixture of petroleum-derived oily sludge and biomass

An innovative way of producing micro-mesoporous enriched active carbon (AC) materials from mixtures of petroleum industrial waste (oily sludge) and agricultural residue (rice husk) is presented. The quality of the products was evaluated by N2 adsorption–desorption isotherms and methylene blue (MB) adsorption tests. The asphaltene content of the oily sludge significantly affected the AC's specific surface area. The higher asphaltene content led to a higher specific surface area (2575m2/g) than that observed for the mixture with a lower asphaltene content (1849m2/g). Moreover, the ACs derived from mixtures of raw materials exhibited lower microporosity levels than those prepared with only oily sludge or rick husk. This may have been caused by the asphaltenes contained in oily sludge forming a carbon skeleton with the ash from the rice husk wrapped inside, generating more mesopores. The products prepared from the mixture also possessed far more oxygen-containing functional groups than AC produced from oily sludge alone. Meanwhile, the cellulose in the rice husk appeared to increase the amount of oxygen-functional groups in the AC products. The highest MB adsorption capabilities for the two AC samples were 588.24 and 757.58mg/g for AC-S1-3 and AC-S2-3, respectively. The Langmuir model fitted the experimental data better than the Freundlich model, suggesting the process can be described as homogeneous monolayer adsorption. X-ray diffraction and X-ray photoelectron spectroscopy data revealed the amorphous nature of the carbon in the AC products. Overall, mixtures of oily sludge and rice husk offer a promising option for preparing porous AC.