Bagasse fly ash (BFA) is one of the important wastes generated in the sugar industry; it has been studied as a prospective low-cost adsorbent in the removal of congo red (CR) from aqueous solutions. Chemical treatment with H2O2 was applied in order to modify the adsorbability of the raw BFA. Batch studies were performed to evaluate the influence of various experimental parameters such as dye solution pH, contact time, adsorbent dose, and temperature. Both the adsorbents were characterized by Fourier-transform infrared spectrometer, energy-dispersive X-ray spectrophotometer and nitrogen adsorption at 77 K. Equilibrium isotherms for the adsorption of CR were analyzed by Langmuir, Freundlich and Temkin models using non-linear regression technique. Intraparticle diffusion seems to control the CR removal process. The obtained experimental data can be well described by Langmuir and also followed second order kinetic models. The calculated thermodynamic parameters indicate the feasibility of the adsorption process for the studied adsorbents. The results indicate that BFA can be efficiently used for the treatment of waste water containing dyes.

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The texturalparameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77K. The chemistryof the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygengroups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303K. Two processeswere investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at variousinitial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH<2.5, sorption decreases because of the protoncompetition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH>2.5 is due to proton insufficiencyand to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factorin determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.