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Dried ground bagasse, impregnated with 50% inorganic acids and carbonized at 500°C, showed the sequence H3PO4 > H2SO4 > HCl > HNO3, with respect to the efficiency of activation. Treatment with phosphoric acid of various concentrations (30–50 wt%) was followed by carbonization at 300–500°C for 3 h. Pore structure parameters were determined from the low‐temperature adsorption of nitrogen, by applying the BET and αs methods. Activated carbons obtained at low temperatures are essentially microporous with a low degree of mesoporosity. At higher temperatures products of higher surface area and total pore volume with developed mesoporosity and low microporosity are formed. An increase in the period of carbonization leads to a small decrease in both surface area and pore volume. Activated carbons with surface areas > 1000 m2 g−1 and mean pore dimensions around 2·0 nm, suitable for various purposes, are thus obtained.

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Activated carbons were prepared from olive oil solid wastes by treatment in different schemes: impregnation with H 3 PO 4 followed by pyrolysis at 300±700°C, by steam pyrolysis at 600± 700°C, or by conventional steam activation at 850°C. Porosity characteristics were determined by analysis of nitrogen adsorption isotherms, and carbons of widely different properties and surface pH values were obtained. Decomposition of H 2 O 2 in dilute unbuffered solution was followed by measuring evolved oxygen volumetrically. First-order kinetics was followed, and the catalytic rate coef®cients were evaluated. The carbons tested showed appreciable activity where evolved oxygen attained %10% of the stoichiometric amount in 1 h. The degree of decomposition showed inverse dependence on surface area, pore volume and mean pore dimensions. The chemical nature of the surface, rather than the porosity characteristics, was the principal factor in enhancing the disproportionation of H 2 O 2 on the activated carbon surface.

The effectiveness of alkali-acid modification in enhancement the adsorption capacity of rice straw (RS) for removing a basic dye was studied. The obtained adsorbents were characterized by slurry pH, pHPZC, iodine number, methylene blue number, FTIR, and SEM analyses. Adsorption of methylene blue (MB) was described by the Langmuir, Freundlich, Tempkin, and Redlich-Peterson isotherm models. Effects of contact time, initial concentration of MB dye, pH of solution, adsorbent dose, salt concentration of NaCl, and desorbing agents on the removal of MB were reported. Kinetic studies were analyzed using the pseudo-first-order, pseudo-second-order, and the intraparticle diffusion models and were found to follow closely the pseudo-second-order model. Equilibrium data were best represented by the Langmuir and Redlich-Peterson isotherms. The adsorption capacities were varied between 32.6 and 131.5 mg/g for untreated and treated RS samples with NaOH-1M citric acid (ARS-1C), respectively. Adsorption behavior of the ARS-1C sample was experimented in a binary mixture containing methylene blue (basic) and reactive blue 19 (acidic) dyes which showed its ability to remove MB higher than RB19. Overall, the results indicate that the alkali-acid treatment proved to be potential modification for producing effective low-cost adsorbents for the removal of the basic dyes from wastewater.