Tailoring activated carbon by surface chemical modification with O, S, and N containing molecules

Abstract

In this work the surface of activated carbon was chemically modified in order to introduce O, S and N containing groups. The activated carbon surface was selectively oxidized with concentrated HNO 3 under controlled conditions. Characterization by thermogravimetric analyses, infrared spectroscopy and NaOH titration suggested the formation of mainly -COOH and small amounts of -OH groups, with concentration of approximately 4.10 21 groups/g of carbon. These -COOH functionalized carbons showed high adsorption capacity for metal cations in aqueous solution in the following order: Pb ]. These -COOH surf groups can be reacted with SOCl 2 to produce a surface acylchloride group, -COCl. This surface -COCl group proved to be a very reactive and versatile intermediate for the grafting of different S and N containing molecules onto the carbon surface, such as 1,2-ethaneditiol (EDT-, HSCH 2 CH 2 SH) 1,7-dimercapto-4-thioheptane (DMTH-HSCH 2 CH 2 CH 2 SCH 2 CH 2 CH 2 SH) or 1,2-ethylenediamine (EDA-NH 2 CH 2 CH 2 NH 2 ) and triethyltetraamine, TEA (H 2 NCH 2 CH 2 NHCH 2 CH 2 NHCH 2 CH 2 NH 2 ). The characterization of these materials was carried out by TG, IR and TPDMS (Temperature Programmed Decomposition Mass Spectrometry) experiments suggesting the formation of thioesther and amide surface groups, i.e. -COSR and -CONHR, with yields of approximately 50 and 75% for the reaction with DME and EDA, respectively. Preliminary adsorption experiments showed that these materials can efficiently remove metals such as Pb +2 , Cu +2 and Ni +2 from aqueous medium.

Surface Modification of Commercial Activated Carbon (CAG) for the Adsorption of Benzene and Toluene

“…In CA-2, the lowerin specific surface area is due to partial or complete blockage of oxygen in the complex pore wall [29] [30]. Similar results were reported [31] [32]. Table 2 shows the results obtained for the determination of surface groups using the Boehm method.…”

Adsorption of mercury (II) from liquid solutions using modified activated carbons

“…The situation is further complicated because the type of species preferentially adsorbed and the extent of adsorption may depend on the state of ionization of the surface which, in turn, is dependent on the solution pH 24 . If the pH of an effluent cannot be modified (for example, when great volumes of liquid have to be decontamined or when this modification produces an environmental problem), the capture of a contaminant can be enhanced by surface modification of the adsorbent by means of suitable treatments [25][26][27][28][29] . In other cases it is possible to change the pH of the solution in order to improve the adsorption.…”

Implementation of carbon nanomodification for sorption materials

“…A promising route for developing effective sorbents is their modification with carbon nanomaterials, in particular, carbon nanotubes (CNTs). The most common sorbents are activated carbon (AC) and zeolites, the modification of which substantially increases their adsorption activity [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

“…As a result of the modification, the surface reactivity, chemical, physical and structural properties of the AC change [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”