Spent Calgon Filtrasorb activated carbon (SAC) from glycerine deodorization unit was evaluated for the removal of methylene blue (MB). The SAC was used without further modification. The SAC was characterized for BET surface area, pH, pHpzc and FTIR to determine the textural and chemical properties of SAC. The batch adsorption study of MB was carried out under different initial concentrations (5–500 mg/L), pH (2–11) and contact time (0–200 h). The SAC was found to have high BET surface area, pore volume and average pore diameter of 735 m2/g, 0.292 cm3/g and 2.56 nm, respectively. The properties of SAC contributed to high MB adsorption capacity of 283 mg/g. The equilibrium data fitted well with Langmuir model, indicating monolayer adsorption; while the activation energy (Ea) of Dubinin–Radushkevitch (D–R) model is lower than 8 kJ/mol, signifying physisorption. The adsorption kinetics was best illustrated by pseudo-second-order model, while the intraparticle diffusion and Boyd models suggested that film diffusion is the rate-controlling step. These findings showed that Calgon Filtrasorb SAC from glycerine deodorization unit can be potentially reused an adsorbent for the removal of dyes.

The present work is aimed at evaluating the kinetics and dynamic adsorption of methylene blue by CO2- activated carbon gels. The carbon gels were characterized by textural properties, thermal degradation and surface chemistry. The result shows that the carbon gels are highly microporous with surface area of 514 m2/g and 745 m2/g for resorcinol-to-catalyst ratios of 1000 (AC1) and 2000 (AC2), respectively. The kinetics data could be described by pseudo-first-order model, with a longer duration to attain equilibrium due to restricted pore diffusion as concentration increases. Also, AC1 exhibits insignificant kinetics with fluctuating adsorption with time at concentrations of 20 and 25 mg/L. However, AC1 reveals a better performance than AC2 in dynamic adsorption due to concentration gradient for molecules diffusion to active sites. The applicability of Yoon–Nelson and Thomas models indicates that the dynamic adsorption is controlled by external and internal diffusion.

The aim of this work was to evaluate the dielectric properties of impregnated and activated palm kernel shells (PKSs) samples using two activating agents, potassium carbonate (K2CO3) and sodium hydroxide (NaOH), at three impregnation ratios. The materials were characterized by moisture content, carbon content, ash content, thermal profile and functional groups. The dielectric properties were examined using an open-ended coaxial probe method at various microwave frequencies (1–6 GHz) and temperatures (25, 35, and 45°C). The results show that the dielectric properties varied with frequency, temperature, moisture content, carbon content and mass ratio of the ionic solids. PKSK1.75 (PKS impregnated with K2CO3 at a mass ratio of 1.75) and PKSN1.5 (PKS impregnated with NaOH at a mass ratio of 1.5) exhibited a high loss tangent (tan δ) indicating the effectiveness of these materials to be heated by microwaves. K2CO3 and NaOH can act as a microwave absorber to enhance the efficiency of microwave heating for low loss PKSs. Materials with a high moisture content exhibit a high loss tangent but low penetration depth. The interplay of multiple operating frequencies is suggested to promote better microwave heating by considering the changes in the materials characteristics.