The effect of the molecular structure of dyes Eriochrome Black T and Bromophenol Blue on their adsorption on the surface of activated carbon manufactured from locally available biosorbent has been studied. Batch experiments were performed to investigate factors that may affect the adsorption process. The effect of stirring rate was investigated in the range 0–240 rpm, with an initial concentration of 4–100 mg/l and a stirring time of 0–400 min. The mechanism and rate of adsorption were investigated for both dyes using pseudo‐first‐order, pseudo‐second‐order, intraparticle diffusion, and liquid film diffusion models. The monolayer adsorption capacities for Eriochrome Black T and Bromophenol Blue were found to be 36.5 and 39.68 mg/g respectively. The difference in dye uptake was attributed to the presence of the electron‐withdrawing bromine group in Bromophenol Blue. Results showed that the Langmuir isotherm best fitted the adsorption of the two dyes on the prepared activated carbon. The pseudo‐second‐order model best fitted the experimental data, and liquid film diffusion and intraparticle diffusion were the controlling adsorption mechanisms.

Date pits were used as a low-cost adsorbent to study the effective removal of copper (II) ions in an aqueous solution on the basis of adsorption kinetics and isotherm equations. Before and after the adsorption process, the date pits were characterized by electron scanning microscope (ESM) as well as Infrared spectroscopy (IR). The effects of the pH, zero point of charge, the adsorbent mass, and the adsorbent particle size on the adsorption of copper (II) were also studied. Equilibrium data were analyzed using different isotherms models. The adsorption kinetics data were evaluated by the pseudo-first-order, second-order kinetic, Elovich and intraparticle diffusion models. Adsorption isotherm analysis data fitted well to the Freundlich model with a maximum adsorption capacity of 3.27 mg/g. The kinetic experimental data correlated well with the pseudo-second-order kinetic model, which indicated that chemisorption processes could be responsible for adsorption. The results demonstrated that date pits have potential to be employed as an effective adsorbent for the removal of copper (II) from aqueous solutions. The copper-loaded adsorbent was investigated for further usage as an adsorbent for the removal of methylene blue from colored water. The adsorption of methylene blue increased 3-15% depending on the mass of adsorbent used.

Hexavalent chromium Cr(VI), a constituent of wastewater from many industries, is regulated by the Environmental Protection Agency (EPA) as one of the priority pollutants. Adsorption is an important technique that can be used for Cr(VI) removal from wastewater. The challenge in adsorption techniques is to find a cheap, widely available adsorbent that has a high adsorption capacity to Cr(VI). Dates stones (DS) and palm fiber (PF) are two agricultural wastes that are produced from palm trees. These adsorbent materials were tested in batch systems to investigate the different factors that may affect the adsorption process, e.g. adsorbent dose, initial adsorbate concentration, pH of aqueous solution and agitation time. Equilibrium models tested include Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. Freundlich adsorption isotherm was found to best fit the experimental data. The maximum adsorption capacities obtained for DS and PF were 16 and 6 mg/g, respectively. Kinetic studies indicated that the adsorption of Cr(VI) on both DS and PF was fast in the first stage of the adsorption process. The equilibrium was reached in less than 2 h for both adsorption systems. The adsorption process was found to be second order with both adsorbent and adsorbate concentration to affect the adsorption process. Film diffusion and intraparticle diffusion models were found to simultaneously influence the adsorption. The adsorption process was found to be favorable and of physical nature.

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