Adsorption heavy metal ions

In a study of the adsorption of soap and several synthetic surfactants on a variety of textile fibers, it was found that cotton and nylon adsorbed less surfactant than wool under comparable conditions (59). Among the various surfactants, the cationic types were adsorbed to the greatest extent, whereas nonionic types were adsorbed least. The adsorption of nonionic surfactants decreased with increasing length of the polyoxyethylene chain. When soaps were adsorbed, the fatty acid and the aLkaU behaved more or less independently just as they did when adsorbed on carbon. The adsorption of sodium oleate by cotton has been shown independently to result in the deposition of acid soap (a composition intermediate between the free fatty acid and the sodium salt), if no heavy-metal ions are present in the system (60). In hard water, the adsorbate has large proportions of lime soap. 

Spirodela intermedia, L. minor, and P. stratiotes were able to remove Pb(II), Cd(II), Ni(II), Cu(II), and Zn(II), although the two former ions were removed more efficiently. Data fitted the Langmuir model only for Ni and Cd, but the Freundlich isotherm for all metals tested. The adsorption capacity values (K ) showed that Pb was the metal more efficiently removed from water solution (166.49 and 447.95 mg/g for S. intermedia and L. minor, respectively). The adsorption process for the three species studied followed first-order kinetics. The mechanism involved in biosorption resulted in an ion-exchange process between monovalent metals as counterions present in the macrophytes biomass and heavy metal ions and protons taken up from water.112... 

Adsorption of heavy metal ions to the surface of goethite and of natural particles... 

Abstract Recently, the interest on biomaterials and especially in tannins was growing and some attractive results were obtained in the adsorption of some metals by tannin adsorbents. Tannins are widely distributed in nature and have multiple adjacent polyhydroxyphenyl groups in their chemical structure which have extremely high afiSnity for heavy metal ions. This study will describe how tannin can be used as an effective zinc and lead sorbent by the use of tannin resins. Batch method was used in the experiments in which pH profde, adsorption time, adsorbent/liquid ratios, initial concentration of metal ions, adsorbent amount and temperature were investigated to determine binding properties of adsorbent for the Zn(II) and Pb(ll) ions. 

Effect of initial pH on adsorption of Pb + ions were investigated as follows 0.5 g of the resin was weighed and 100 mL of a heavy metal ion solution was added. The pH of each solution was adjusted to desired values. After stirring 5 h the reaction mixture was filtered through membrane filter to remove particulates and analyzed with an AAS. 

Recently, the interest on biomaterials and especially in tannins was growing and some attract results were obtained in the adsorption of some metals by tannin adsorbents [18]. Tannins are widely distributed in nature and have multiple adjacent polyhydroxyphenyl groups in their chemical stracture which have extremely high affinity for heavy metal ions [16, 19]. 

Gao B, An F, Tiu K. Studies on Chelating Adsorption Properties of Novel Composite Material Polyethyleneimine/silica Gel for Heavy-metal Ions. Applied Surface Science 2006 253 1946-1952. 

Considering first adsorption of metal ions or neutral species directly on the snbstrate, there are a nnmber of possible mechanisms for this process. Most simply, there will an equilibrinm between metal species in solution and a solid snr-face leading to dynamic adsorption of the metal. Adsorption of metal ions onto solid snrfaces has been extensively studied, to a large extent becanse of the nse of oxide snrfaces to adsorb heavy metal ions and remove them from solntion (see Ref. 55 for an example and list of other references on this snbject). This adsorption may go even farther with ion exchange between the solntion metal ions and ions in the substrate (again, glass is a good example of where this may occnr). 

Say, R., Emir, S Garipcan, B. et al. (2003a) Novel methacryloylamidophenylalanine functionalized porous chelating beads for adsorption of heavy metal ions. Advances in Polymer Technology, 22(4), 355-64. 

For naphthalene black there is a perfect eluant, composed of equal parts ethanol and 0.5 N sodium hydroxide. The alkaline pH and the ethanol are required to overcome adsorption of protein to paper, but as alkaline solutions of the dye are very unstable, probably due to the presence of traces of heavy metal ions, the addition of 500 mg of Com-plexon (EDTA) per liter is required (D3 Fig. 26). In this condition an alkaline solution of amido black is stable for indefinite periods of time. 

Keywords heavy metal ions MCM-41 MCM-48 mercury adsorption mesoporous organosilicas ordered mesoporous silicas SBA-15... 

Porous materials with chemically modified surfaces have been extensively studied as adsorbents for heavy metal ions from water (see the review by Jal et al.2 and references therein). There is a continuously growing demand for adsorbents which are non-swelling, thermally and hydrothermally stable, exhibit large adsorption capacity, fast kinetics and high affinity towards heavy metal ions. Discovery of self-assembled ordered mesoporous silicas (OMSs)3 opened enormous opportunities for the design and synthesis of highly selective and efficient adsorbents for heavy metal ions. 

A. M. Liu, K. Hidajat, S. Kawi, and D. Y. Zhao, A new class of hybrid mesoporous materials with functionalized organic monolayers for selective adsorption of heavy metal ions, Chem. Commun. 1145-1146 (2000). 

INFLUENCE OF THE NATURE OF ACTIVE SURFACE SITES OF HIGHLY DISPERSE OXIDES ON ADSORPTION OF HEAVY METAL IONS... 

A common theme throughout this volume involves the adsorption and interfacial, especially biointerfacial, behaviour of all of the above mentioned nanomaterials. For environmental and human protection, the adsorption of heavy metal ions, toxins, pollutants, drugs, chemical warfare agents, narcotics, etc. is often desirable. A healthy mix of experimental and theoretical approaches to address these problems is described in various contributions. In other cases the application of materials, particularly for biomedical applications, requires a surface rendered inactive to adsorption for long term biocompatibility. Adsorption, surface chemistry, and particle size also plays an important role in the toxicological behaviour of nanoparticles, a cause for concern in the application of nanomaterials. Each one of these issues is addressed in one or more contributions in this volume. 

Solidification with cement generally is accomplished with a Portland cement and other additives. The quantity of cement can be varied according to the amount of moisture in the waste. Heavy metal cations in the waste form insoluble carbonates and hydroxides at the high pH of the mixture. The surface of the hardened mass can be coated with asphalt or other material to reduce leaching of hazardous components. If the waste is mixed with anhydrous cement and water there is the possibility of ions incorporation in the cement structure during the hydrolysis process. Heavy metal ions could bind with the cement by the process of chemisorption, precipitation, surface adsorption,... 

Adsorption at the solution-carbon interface is already widely used on a large scale for water treatment, decolorizing, gold recovery, etc. (Derbyshire et al., 1995). In addition to these well-established applications, considerable interest is now being shown in the potential use of activated carbons for the removal of a wide range of pollutants such as aromatic hydrocarbons, humic acids and heavy metal ions (Costa et al., 1988 Youssef et al., 1996) and for the treatment of radioactive waste (Qadeer and Saleem, 1997). The aims of the applied research are generally to optimize the performance of the available commercial grades of activated carbon, to develop new products and to elucidate the mechanisms of adsorption (Blasinski et al., 1990). 

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