| Potato residue is one of the most undesired waste materials during starch production from potato which mainly consists of starch, cellulose, hemicellulose and pectin. It would be mildewed, produce toxic substances and cause serious environmental pollution for soil, water and air if they are disposed of inadequately.Activated carbon(AC) is the most widely used adsorbent for removal of pollutants in water. However, commercial AC is relatively expensive and hampered its widely application in wastewater treatment. Therefore, to seek low cost adsorbents is still an attractive goal. Dyes are widely used in industries involving paper, plastics, textiles,cosmetics, etc. In particular, the acid dyes of the monoazo and anthraquinone classes are used in the dyeing of wool, silk, acrylic and nylon, at the same time, a large number of industrial wastewater is discharged. In addition, dyes are usually found to coexist with heavy metal ions in wastewater. Presence of these dyes and metals at elevated levels in wastewater is potentially toxic to the environment due to their detrimental effects to humans and other living organisms. Therefore, the removal of dyes and heavy metal ions from wastewater is currently one of the more urgent environmental concerns we are facing.This study was conducted to prepare a low cost and highly efficient AC(PRAC)from potato residue. The influence of the activation parameters such as carbonization temperatures and the impregnation ratios were investigated. The PRAC was essentially mesoporous under the optimized conditions. The BET surface area, total pore volume and mesopore volume were as high as 1357 m2/g, 1.065 cm3/g and 0.982cm3/g, respectively. The properties of the carbon samples that were prepared under oxygen-limited conditions and N2-atmosphere conditions were compared. The PRAC was used to adsorb methylene blue(qe = 540 mg/g), and the results showed that the prepared PRAC is an effective adsorbent for the removal of the organic dye. The experimental results indicated that the use of potato residue as a precursor material for the preparation of AC was feasible.In order to explore the adsorption of PRAC, the adsorption of methylene blue(MB) and acid blue 80(AB80) onto PRAC were carried out in this work. Theadsorption kinetics of pseudo-first order and pseudo-second order were used for the kinetic studies. The experimental equilibrium data were analyzed using the isotherms of Langmuir, Freundlich, Redlich-Peterson, Toth and Sips. The thermodynamic parameters were calculated, and showed that the adsorption of these two kinds of dyes were thermodynamically spontaneous nature and endothermic nature. The PRAC is a fast and effective adsorbent for removing cationic dye from aqueous solutions.In order to further study the PRAC in practical application of sewage treatment,the adsorption behavior of AB80 and two heavy metal ions(Cu2+/ Ni2+) onto PRAC was investigated. And a novel synergic adsorption process of acid blue 80 dye(AB80)and heavy metal ions(Cu2+ or Ni2+) on PRAC was founded. The results indicated that the maximum adsorption capacity of PRAC for AB80 and Cu2+were 294.7 mg/g and45.0 mg/g in the AB80-Cu2+ system, respectively. In the mono-component system, the values were 173.0 mg/g and 26.8 mg/g, respectively. Compared with mono-component system, the AB80 and Cu2+showed good synergistic effect on PRAC. The similarly result was revealed in the AB80-Ni2+ system. For a binary system, the adsorption isotherm of AB80 and heavy metal ions followed the non-modified Sips model, and the adsorption kinetic models followed the pseudo-second order kinetic model. The effect of pH also was discussed, and showed significant role in the binary-component system adsorption. The selectivity in synergic adsorption was discussed. FE-SEM/EDX and XPS were used to characterize PRAC with and without adsorbed dye and heavy metal ions, possible mechanisms of AB80 and heavy metal ions synergic adsorption process were proposed. |
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