Mesoporous activated carbon from industrial laundry sewage sludge: Adsorption studies of reactive dye Remazol Brilliant Blue R

• Mesoporous activated carbon was produced from industrial laundry sewage sludge (AC).
• Surface area of AC decreased with increase of activation temperature.
• Kinetic, isotherm and thermodynamic studies for Remazol Brilliant Blue R removal were evaluated.
• AC showed maximum monolayer adsorption capacity of 33.5 mg g−1 at 25 °C.
• Spent activated carbon (ACsp) was submitted to thermal regeneration cycles.

Mesoporous activated carbon (AC) was prepared from sewage sludge of industrial laundry by slow pyrolysis followed of physical activation with CO2 and applied to remove reactive dye Remazol Brillant Blue R (RBBR) from aqueous solutions. The effect of activation temperature was investigated. The materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms. The ACs prepared at activation temperatures of 750 °C (AC750), 800 °C (AC800) and 850 °C (AC850) exhibited BET surface areas (SBET) of 159 m2 g−1, 156 m2 g−1 and 65 m2 g−1, respectively, and mesoporous features with average pore diameters ranging from 4.56 to 5.88 nm. The SEM images indicated the formation of cavities on the surfaces of ACs with increasing temperature. The XRD patterns showed the presence of minerals in ACs and sewage sludge such as quartz, muscovite, dolomite and calcite. Inorganic and organic contents were evidenced by TGA, and surface groups by FT-IR. The values of pHPZC indicated basic characteristics for AC750, and acidic for AC800 and AC850. The AC750 was applied in the RBBR adsorption from aqueous solution. Adsorption kinetics and adsorption equilibrium showed that the pseudo-second order and Freundlich models were best fitted to experimental data. The Langmuir monolayer maximum adsorption capacity was 33.47 mg g−1. The thermodynamic parameters indicated the adsorption is a spontaneous process and favored at higher temperatures (endothermic reaction). The thermal regeneration of spent AC750 showed it can be reused on adsorption processes.

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