Adsorption of hexavalent chromium from aqueous solutions by wheat bran

Nanosilica particles modified by Schiff base ligands 3-methoxy salicylaldimine propyl triethoxysilane (MNS 1 ), 5-bromo salicylaldimine propyl triethoxysilane (MNS 2 ) and 3-hydroxy salicylaldimine propyl triethoxysilane (MNS 3 ) were prepared, and their potential for separation of copper, lead, zinc, cadmium, cobalt and nickel ions from aqueous solutions was examined. The effect of parameters influencing adsorption efficiency including aqueous-phase pH, amount of adsorbent, stirring time and initial concentration of the metal ions was assessed and discussed. Although MNS 1 and MNS 3 removed lead ions efficiently, all adsorbents showed strong selectivity toward copper ions. It was shown that, under some circumstances, MNS 3 decreased the amount of other ions, particularly cobalt, in the aqueous phase. The adsorbents were also applied for removal of copper and lead ions from real samples. Possible quantitative desorption of the metal ions loaded onto the adsorbents suggests their multiple uses in adsorption-desorption process. Investigation of temperature dependency of the process led to determination of the DH°, DS°and DG°values. This investigation indicates that the adsorption of copper ions onto the all studied adsorbents and lead ions onto MNS 1 and MNS 3 is endothermic. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were tested to describe the equilibrium data. Pseudo-first-order, pseudo-secondorder, Elovich and intra-particle diffusion equations were applied to study the kinetics of copper and lead adsorption onto the modified nanoparticles. This investigation indicates that the process for all adsorbents follows pseudosecond-order kinetics and suggests a chemisorption mechanism for the adsorption processes by the studied adsorbents.

Section: Kinetics Of Adsorptionmentioning

confidence: 99%

Adsorption efficiency, thermodynamics and kinetics of Schiff base-modified nanoparticles for removal of heavy metals

Moftakhar

Yaftian

Ghorbanloo

2016

“…The slope and intercept of the plot of log (q e -q t ) versus t are used to determine the pseudo-firstorder rate constant K ads and q e , respectively. Pseudo-second-order rate equation (Nameni et al 2008) can be expressed in the following form:…”

Section: Resultsmentioning

confidence: 99%

“…[1), which suggests the favorability of multilayered sorption process (Nameni et al 2008). The value of K F was found to be 26.17 L g -1 , which indicated that resin has a high adsorption capacity for Cr(VI) solution.…”

Section: Effect Of Initial Metal Concentration On Removalmentioning

confidence: 99%

Removal of hazardous hexavalent chromium from aqueous solution using divinylbenzene copolymer resin

Bajpai

Dey

Jha

et al. 2012

This paper presents the removal of hazardous hexavalent chromium from liquid waste streams using divinylbenzene copolymer resin Amberlite IRA 96. Important sorption parameters such as contact time, pH, resin dosage and initial metal concentration were studied at 30°C. The kinetic study was conducted using pseudo-first and pseudo-second-order kinetics at 30°C. The sorption process was found to be pH dependent. Maximum removal was obtained at pH 2 under optimized conditions. The sorption process was rapid and 99 % of the removal was achieved in first 30 min. The equilibrium data were fitted to both Langmuir and Freundlich models. The better regression coefficient (R 2 ) in Freundlich model suggests the multilayer sorption process. The value of Gibbs free energy for sorption process was found to be -12.394 kJmol -1 . The negative value indicated the spontaneity of the sorption process. Scanning electron microscope and energy dispersive X-ray spectroscopy studies were conducted to find the role of surface morphology during sorption process. The Fourier transform infrared study was conducted to identify the functional groups responsible for interaction between the resin and chromium. Desorption and regeneration studies were also carried out.

“…On the other hand, their structure, phase composition, chemical stability, water insolubility and mechanical strength render them suitable for preparing valuable materials for different uses. Agricultural wastes can be applied as biosorbents, directly or after activation (Sumathi et al 2005;Dias et al 2007;Ioannidou and Zabaniotou 2007;Nameni et al 2008;Garcia-Reyes et al 2009;Gupta et al 2012;Vassileva et al 2013;Yuvaraja et al 2014). The advantages of biosorbents are biodegradability and good adsorption properties due to their morphology and surface functional groups (Ngah and Hanafiah 2008;Ali 2010;Ali et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Ag+ ions on hydrolyzed lignocellulosic materials based on willow, paulownia, wheat straw and maize stalks

Vassileva

Radoykova

Detcheva

et al. 2016

In the present work, the adsorption of Ag ? ions on hydrolyzed plant biomass (willow, paulownia, wheat straw and maize stalks) was investigated. Chemical analyses were performed to establish the composition of the obtained materials. Adsorption mechanism, adsorption sites and specific surface areas of these materials were examined by BET analysis, IR spectroscopy, XPS and EPR. The effects of contact time, acidity of initial solutions and Ag ? ion concentrations were followed. Pseudo-firstorder, pseudo-second-order and intra-particle diffusion models were used to analyze kinetic data. In all cases, the adsorption was significantly affected by the pH value. Different types of adsorption isotherms of Ag ? ions (either Langmuir or Freundlich) were registered depending on the adsorbing material. The adsorption mechanism is complex, and the process passes through different stages as clustering of Ag ? ions and formation of elemental Ag. The maximal adsorption capacities varied from 2.05 to 6.07 mg g -1 . The obtained results revealed that the examined waste lignocellulosic materials are promising adsorbents for Ag ? ions.