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Purpose The purpose of this paper is to focus on the removal of hexavalent chromium [Cr(VI)] from wastewater by using activated carbon-supported Fe catalysts derived from walnut shell prepared using a wetness impregnation process. The different conditions of preparation such as impregnation rate and calcination conditions (temperature and time) were optimized to determine their effects on the catalyst’s characteristics. Design/methodology/approach The catalyst samples were characterized using thermogravimetric analysis, scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption of Cr(VI) by using using activated carbon supported Fe catalysts derived from walnut shell as an adsorbent and catalyst was investigated under different adsorption conditions. The parameters studied were contact time, adsorbent dose, solution pH and initial concentrations. Findings Results showed that higher adsorption capacity and rapid kinetics were obtained when the activated walnut shell was impregnated with Fe at 5 per cent and calcined under N2 flow at 400°C for 2 h. The adsorption isotherms data were analyzed with Langmuir and Freundlich models. The better fit is obtained with the Langmuir model with a maximum adsorption capacity of 29.67 mg/g for Cr(VI) on Fe5-AWS at pH 2.0. Originality/value A comparison of two kinetic models shows that the adsorption isotherms system is better described by the pseudo-first-order kinetic model.

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In this work, an activated carbon derived from date pits and stems (DPSAC) was prepared by physical activation under N 2 and used as a support of cobalt transition metals, by wetness impregnation at different Co content and different calcination temperatures. The optimal operator conditions were 20 wt% cobalt impregnation ratio and 300°C calcination temperature. The grafted material was characterized by methods: thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform of infrared spectroscopy (FTIR). The activated carbon (DPSAC) and grafted activated carbon (Co/DPSAC) were realized on adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution , it was found that the cobalt-grafted dates pits and stems activated carbon promoted the 2,4-D adsorption kinetics, The Langmuir and Freundlich isotherms models were applied for the adsorption results. The rate of adsorption of 2,4-D onto (DPSAC) and (Co/DPSAC) were estimated and described using a pseudo-second order model.

Using physical activation, modified apple wastes with Al 13 polycation were utilized such a feedstock's for activated carbon production .thence, The characteristics of synthesized materials were: N 2 adsorption/desorption , Scanning electron microscopy, and Fourier-transform infrared analyses. AS a beginning, one studied the effect of Al 13 grafting on textural and chemical surface characteristics of activate,d carbons-Al 13 generated . The increasing Al 13 content has major inffluences on the porous structure of the prepared activated carbon; it causes more structurale and intensifies the surface zone and the pore volume (484 m 2 /g, micropore area of 400 m 2 /g and microporous volume of 0.185 cm 3 /g is the best surface area).ALSO The methyl orange adsorption performance of the received adsorbent was investigated to identify the role of Al 13 , especially its particular structure and high positive charge (+7). Adsorption performance of the grafted activated carbon was significantly enhanced. Raising charges at carbons materials surface by Al 13 grafting improved the methyl orange adsorption kinetics. The adsorption data was relevant to Langmuir, Freundlich and Temkin models. The results indicated that the adsorption data belonging better to the Langmuir isotherm model. The prepared activated carbon-Al 13 founded to be an efficient material for anionic dye removed from wastewater.