Valorization of biomass waste to engineered activated biochar by microwave pyrolysis: Progress, challenges, and future directions

Recent advances in applications of activated carbon from biowaste for wastewater treatment: a short review.

Removal of methylene blue from aqueous solution by modified bamboo hydrochar.

In this study, using coconut fibers as raw material, activated carbon fibers were prepared via carbonization and KOH activation processes. The morphology, composition, specific surface area, pore structure and thermal stability of the resulting activated carbon fibers were systematically characterized. It was found that the activation process increases the specific surface area of carbon fibers to a greater extent via formation of a large number of micropores (0.7–1.8 nm) and a certain amount of slit-shaped mesopores (2–9 nm). The specific surface area and the pore volume of the activated carbon fibers reach 1556 m2 g−1 and 0.72 cm3 g−1, respectively. The activation process can also decompose the tar deposits formed after the carbonization process by pyrolysis, making the surface of the activated carbon fibers smoother. To study the adsorption properties of the as-prepared activated carbon fibers, the adsorption capacities and adsorption kinetics of various organic dyes including methylene blue, Congo red and neutral red were investigated. The adsorption capacities of the dyes increased with the increasing initial dye concentrations, and varied greatly with the pH value of the system. In methylene blue and neutral red systems, the adsorption capacities reach the maximum at pH 9, and in the Congo red system, it reaches the maximum at pH 3. The adsorption capacities of the activated carbon fibers in methylene blue, Congo red and neutral red systems reached equilibrium at 150, 120, and 120 min, and the maximum adsorption capacities were 21.3, 22.1, and 20.7 mg g−1, respectively. The kinetics of the adsorption process was investigated using three models including pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The results indicated that the dynamic adsorption processes of coconut-based activated carbon fibers to methylene blue, Congo red and neutral red were all in accordance with the second-order kinetic model, and the equations are as follows: t/Qt = 0.1028 + t/21.3220, t/Qt = 0.1128 + t/21.5982 and t/Qt = 0.0210 + t/20.6612.

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Coconut-based activated carbon fibers for efficient adsorption of various organic dyes

From pollutant to solution of wastewater pollution: Synthesis of activated carbon from textile sludge for dye adsorption

The preparation of activated carbon fiber (ACF) with cotton as raw precursor via microwave assisted H3PO4 activation was explored in the present study. The influence of microwave power, activation time and acid concentration on the properties of activated carbon fiber was investigated. The ACF with maximum surface area and total pore volume of 1370 m2/g and 0.98 cm3 was prepared at microwave input power of 640 W, activation time of 10 min and H3PO4 concentration of 50% (Wt.). The ACF was tested with methylene blue (MB) dye adsorption and the equilibrium adsorption capacity was 476 mg/g, with the adsorption isotherm following the Langmuir isotherm model. The adsorption kinetic followed the pseudo-second-order kinetic model, while the adsorption mechanism was well described by the film diffusion model. The experimental results indicated the potential of cotton as good precursor for the preparation of ACF with promising adsorption capacity by microwave heating.

Xinyi Liu

Papers

Synthesis of activated carbon fibers from cotton by microwave induced H3PO4 activation