Modeling the sorption of toxic metals on chelant‐impregnated adsorbent

Abstract

IntroductionThe removal of toxic heavy metals such as cadmium, zinc, and lead has become an important concern to manufacturing industries with respect to water purification and wastewater treatment. Several physicochemical technologies have been used for this purpose, including adsorption, ion exchange, and Ž . membrane separation processes Clifford et al., 1986 . Adsorption and ion-exchange processes have been found less expensive than membrane processes for most industrial applications. Most resins have higher affinity for alkaline earth Ž . Ž calcium and magnesium and alkali metals sodium and . potassium , and have poor selectivity for heavy metals. Improving resin selectivity by introducing new types of polymers into the matrix is a complex and expensive process. In comparison, an established technology that proves less expensive for the removal of trace metals, particularly radionuclides and Ž . heavy metals, is granular activated carbon GAC adsorption Ž . Motojima et al., 1978Motojima et al., , 1979aClifford et al., 1986 . Although GAC fixed-bed adsorbers are technologically feasible for the removal of heavy metals, they are not widely Correspondence concerning this article should be addressed to M. Pirbazari. used due to their low adsorbent capacity and questionable Ž . regenerability Clifford et al., 1986 . On the other hand, impregnation or immobilization of a selective chelating agent Ž . such as 8-hydroxyquinoline oxine on activated carbon would Ž provide a superior sorbent material for heavy metals Stevens, . 1987 . The nonpolar oxine is well adsorbed on activated car-Ž . bon, and such surface modified activated carbon SMAC would manifest higher adsorption capacity and easy regener-Ž . ability for heavy metals Vogt, 1948;Motojima et al., 1978 . Among various chelating agents, oxine is highly selective for Cd, Zn, Pb and other heavy metals as compared to alkaline earth and alkali metals present in most waters and wastewa-Ž . ters Stevens, 1987;Abollino et al., 1990 . Additionally, oxine is relatively nontoxic as it has been widely used for medicinal Ž . and agricultural applications Phillips, 1956 . Thus, good selectivity for heavy metal ions, easy adsorbent regenerability, and low toxicity of oxine makes oxine-impregnated SMAC a suitable candidate for the removal of heavy metals. A few studies have been conducted on the application of oxine-impregnated activated carbon for the removal of radionuclides such as Co-58, Co-60, Mn-54, and Fe-57 from nuclear wastes Ž . by coworkers 1978, 1979a,b . These re- May 1999 Vol. 45, No. 5 AIChE Journal 1135searchers observed that oxine-impregnated carbon was significantly more effective in the removal of these radioactive metal ions than pure activated carbon. An important aspect in the use of oxine-impregnated SMAC is the consideration of mechanisms pertaining to the sorption of oxine on activated carbon, and subsequent chelation of metal ions on the adsorbent-impregnated oxine. It is important to note that the sorption of oxine on activated carbon can be attrib...

Acid modified jackfruit wood sawdust as biosorbent for the removal of Fe(II) from aqueous solutions

“…Various methods, such as precipitation, ion exchange, membrane processes, adsorption, coagulation, flotation, etc., have been applied for the removal of heavy metals from aqueous solution [4][5][6][7]. Some of those processes are often restricted because of technical or economic constraints [8].…”

Adsorption of Manganese(II) Ions by EDTA-treated Activated Carbons

“…Nitrogen adsorption isotherms (Nova 2200E or Autosorb-1; Quantachrome, Boyton Beach, FL) conducted at -196 o C were used to characterize the physical properties of the GACs, applying the BET equation over the relative pressure range 0.01-0.1 (Lowell et al 2004) to obtain surface areas, and the DFT and BJH equations to ascertain adsorbent pore-size distributions (Tennant and Mazyck 2003). Pore-size distribution replicates indicated differences of no greater than 6% in the pore volume over the range investigated.…”

“…For example, Ravindran et al (1999) found that pre-adsorbing 8-hydroxyquinoline (oxine) onto Calgon F400 -a bituminous coal-based commercially-available activated carbon -increased the capacity of the carbon towards Cd(II), Zn(II) and Pb(II) ions by at least one order of magnitude. These authors advanced the view that the organic portion of the chelating agent sorbed to the activated carbon through π-π interactions, leaving functional groups available to chelate the aqueous metals.…”

“…It follows, therefore, that increasing the number of Brönsted acid groups would enhance adsorption. For this reason, some researchers have attempted to saturate the carbon surface with functional groups by pre-adsorbing certain organic compounds which are known to chelate metals (Lakov et al 1999;Ravindran et al 1999;Monser and Adhoum 2002;Chen et al 2003;Üçer et al 2005).…”

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“…There are many promising techniques in practice to remove heavy metals from water and have already been reported including; precipitation (Esalah et al 2000), flotation (Zouboulis et al 1997), biosorption Ho et al 2001), membrane separation (Canet et al 2002), adsorption on minerals (Buerge-Weirich et al 2002;Ahmed et al 2002;Chamila et al 2015), Zeolites (Pankaj et al 2015) and activated carbon (Khan et al 2015;Ravindran et al 1999). Many researchers also use Bacteria, fungi and algae for removal of heavy metals (Ankur and Chandrajit 2015;Hossein et al 2015).…”