Removal of Cr(VI) from aqueous solutions by modified walnut shells

Chemical modification of Byrsonima crassifolia with citric acid for the competitive sorption of heavy metals from water

“…Additionally, results also show that the temperature of chemical treatment is a relevant parameter for enhancing the metal uptakes of BC endocarp. Note that the temperature increment of the chemical modification process may increase the possibility of the cross-linking between two cellulosic molecules of BC endocarp (Altun and Pehlivan 2012). In fact, these results suggest that the reaction between citric acid and this biomass is an endothermic process.…”

“…For single metallic solutions, it is clear that the metal-binding properties of treated-biomass samples increase with both the citric acid concentration and the temperature of thermal treatment. During the chemical treatment, the citric acid when heated will dehydrate to yield a reactive anhydride and this anhydride can react with the biomass introducing acidic groups on the surface of BC endocarp (Wing 1996;Marshall et al 1999;Altun and Pehlivan 2012;LeyvaRamos et al 2012). Therefore, the metal uptakes of treated-BC samples are enhanced if a higher citric acid concentration is used.…”

“…In particular, the surface chemistry modification has been recognized as a suitable approach to improving the sorption properties of agroindustrial by-products and wastes for the removal of heavy metals and other priority pollutants from water (Wing 1996;Vaughan et al 2001;Reddad et al 2002;Leyva-Ramos et al 2005;Tan et al 2010;Sajab et al 2011;Altun and Pehlivan 2012;LeyvaRamos et al 2012). Reactions between lignocellulosic biomasses and acids have been used to create alternative materials with satisfactory metal ion binding properties (Vaughan et al 2001).…”

“…Reactions between lignocellulosic biomasses and acids have been used to create alternative materials with satisfactory metal ion binding properties (Vaughan et al 2001). Specifically, the chemical modification using citric acid offers more advantages to react with lignocellulosic materials than other modification agents because it improves the sorption properties and also increases the mechanical strength of the biomass due to the cross-linking (Altun and Pehlivan 2012). In particular, the citric acid may increase the acidic groups on the biomass surface, and, consequently, the capacity of the treated material to bind metallic ions is enhanced because these functional groups play an important role during the removal of these pollutants.…”

Adsorption of C.I. Acid Red 97 dye from aqueous solution onto walnut shell: kinetics, thermodynamics parameters, isotherms

“…Adsorption experiments using walnut shell (WS) as an adsorbent have been reported on other dyes like malachite green (Dahri et al 2014), reactive brilliant red K-2BP (Cao et al 2014) and heavy metals such as Cr(VI) (Altun and Pehlivan 2012). But from the survey of the literature, no information for the adsorption removal of Acid Red 97 (AR97) by WS is available.…”