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Adsorption: Journal of the International Adsorption Society (v.12, #2)
Removal and recovery of vanadium(V) by adsorption onto ZnCl2 activated carbon: Kinetics and isotherms by C. Namasivayam; D. Sangeetha (pp. 103-117).
Adsorption of vanadium(V) from aqueous solution onto ZnCl2 activated carbon developed from coconut coir pith was investigated to assess the possible use of this adsorbent. The influence of various parameters such as agitation time, vanadium concentration, adsorbent dose, pH and temperature has been studied. First, second order, Elovich and Bangham’s models were used to study the adsorption kinetics. The adsorption system follows second order and Bangham’s kinetic models. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms have been employed to analyze the adsorption equilibrium data. Equilibrium adsorption data followed all the four isotherms—Langmuir, Freundlich, D-R and Temkin. The Langmuir adsorption capacity (Q 0) was found to be 24.9 mg g− 1 of the adsorbent. The per cent adsorption was maximum in the pH range 4.0–9.0. The pH effect and desorption studies showed that ion exchange mechanism might be involved in the adsorption process. Thermodynamic parameters such as ΔG 0, ΔH 0 and ΔS 0 for the adsorption were evaluated. Effect of competitive anions in the aqueous solution such as PO4 3 −, SO4 2−, ClO4 −, MoO4 2−, SeO3 2−, NO3 − and Cl− was examined. SEM and FTIR were used to study the surface of vanadium(V) loaded ZnCl2 activated carbon. Removal of vanadium(V) from synthetic ground water was also tested. Results show that ZnCl2 activated coir pith carbon is effective for the removal of vanadium(V) from water.
Keywords: Adsorption; Activated carbon; Vanadium(V); Kinetics; Isotherms; pH; Foreign ions
Preparation and characterization of activated carbons from Sterculia alata nutshell by chemical activation with zinc chloride to remove phenol from wastewater by Kaustubha Mohanty; D. Das; M. N. Biswas (pp. 119-132).
Nutshells of Sterculia alata, a forest waste, were used to prepare activated carbons by zinc chloride activation under four different activation atmospheres, to develop carbons with substantial capability, and to adsorb phenol from wastewater. Experiments were carried out at different chemical ratios (activating agent/precursor). Effect of carbonization temperature and time are the important variables, which had significant effect on the pore structure of carbon. Developed activated carbon was characterized by SEM analysis. Pore volume and surface area were estimated by Hg porosimetry and BET surface area analyses. The carbons showed surface area and micropore volumes of around 712 m2/g and 0.542 cm3/g, respectively. The activated carbon developed shows substantial capability to adsorb phenol from wastewater. The kinetic data were fitted to the models of intraparticle diffusion, pseudo-second order, and Lagergren model and followed more closely the pseudo-second-order chemisorption model. The isotherm equilibrium data were well-fitted by the Langmuir and Freundlich models. The maximum uptake of phenol was found at pH 3.5.
Keywords: Wastewater treatment; Activated carbon; Sterculia alata nutshell; Surface area; Chemical activation; Phenol removal
Removal of Mn(II) and Cd(II) from wastewaters by natural and modified clays by S. M. Dal Bosco; R. S. Jimenez; C. Vignado; J. Fontana; B. Geraldo; F. C. A. Figueiredo; D. Mandelli; W. A. Carvalho (pp. 133-146).
The adsorption capacities of commercial and Brazilian natural clays were evaluated to test their applications in wastewater control. We investigated the process of sorption of manganese(II) and cadmium(II) present in synthetic aqueous effluents, by calculating the adsorption isotherms at 298 K using batch experiments. The influence of temperature and pH on the adsorption process was also studied. Adsorption of metals was best described by a Langmuir isotherm, with values of Q 0 parameter, which is related to the sorption capacity, corresponding to 6.3 mg g− 1 for K-10/Cd(II), 4.8 mg g− 1 for K-10/Mn(II), 11.2 mg g− 1 for NT-25/Cd(II) and 6.0 mg g− 1 for NT-25/Mn(II). We observed two distinct adsorption mechanisms that may influence adsorption. At the first 5 min of interaction, a cation exchange mechanism that takes place at exchange sites located on (001) basal planes is predominant. This process is inhibited by low pH values. After this first and fast step, a second sorption mechanism can be related to formation of inner-sphere surface complexes, which is formed at edges of the clay. The rate constants and the initial sorption rates correlate positively with temperature in all studied systems, denoting the predominance of a physisorption process. The addition of complexing agents that are incorporated within the K10 structure, enhance metal uptake by the adsorbent. The results have shown that both Cd(II) and Mn(II) were totally retained from a 50 mg L− 1 solution when K10 grafted with ammonium pyrrolidinedithiocarbamate (APDC) was used as adsorbent.
Keywords: Modified clays; Brazilian clay; Toxic metals; Adsorption isotherm; Wastewater; Heavy metals
Potassium bromate modification of the granular activated carbon and its effect on nickel adsorption by D. Satapathy; G. S. Natarajan (pp. 147-154).
Granular Activated Carbon (GAC), a commercial adsorbent for the removal of heavy metals was treated chemically with potassium bromate for it’s surface modification and it’s adsorption capacity was investigated with nickel ions. There was an increase in the adsorption capacity of the modified carbon by 90–95% in comparison to the raw granular activated carbon towards nickel ion adsorption. Potassium Bromate oxidation treatment was employed for a period of about 30 mins initially followed by 60 mins and the oxidized carbons were adsorbed with nickel ions. Metal sorption characteristics of as received and modified activated carbons were measured in batch experiments. Batch adsorption was successfully modeled by Langmuir Isotherm Model which indicates monolayer adsorption. The adsorption isotherms also fit well to the Freundlich Model. Effects of pH of initial solution, time of oxidation and mode of treatment on the adsorption process were studied. Experimental results showed that metal uptake increased with an increase in pH and oxidation time. The samples were characterized by Scanning Electron Microscope (SEM) studies and surface area analyzer.
Keywords: Granular Activated Carbon (GAC); Nickel; Potassium bromate; Surface treatment; Isotherm; Kinetics; Batch experiments
Chromium adsorption in olive stone activated carbon by Milton Rogério Pereira; Pedro Augusto Arroyo; Maria Angélica Simões Dornellas de Barros; Viviane Monteiro Sanches; Edson Antonio da Silva; Isabel Maria Fonseca; Rafael García Lovera (pp. 155-162).
In this work, Cr(III) adsorption on activated carbon obtained from olive stones in an upflow fixed-bed column at 30∘C was studied. The flow rate influence on the breakthrough curves at a feed concentration of 0.87 meq/L was investigated in an attempt to minimize the diffusional resistances. Breakthrough curves for a flow range of 2–8 mL/min were obtained at 10.5 cm bed height and inlet diameter of 0.9 cm. The mass transfer parameters indicated that the bed minimal resistance was attained at 2 mL/min. Therefore, the data equilibrium was carried out until the bed was saturated at 2 mL/min. The dynamic system generated a favorable isotherm with a maximum chromium uptake of 0.45 meq/g. A column sorption mathematical model was created considering the axial dispersion in the column and the intraparticle diffusion rate-controlling steps. The isotherm was successfully modeled by the Langmuir equation and the mathematical model described the experimental dynamic data adequately for feed concentrations from 0.26 to 3.29 meq/L.
Keywords: Chromium; Activated carbon; Olive stones; Adsorption; Breakthrough