Adsorption of microcystins by carbon nanotubes

Abstract

The production of cyanobacterial toxins microcystins (MCs) by cyanobacterial bloom which may promote the growth of tumor in human liver is a growing environmental problem worldwide. In this paper, the adsorption of MC-RR and LR, which were extracted from cyanobacterial cells in Dianchi Lake in China, by carbon nanotubes (CNTs), wood-based activated carbon (ACs) and clays were investigated. Compared with ACs and clay materials of sepiolite, kaolinite and talc tested, CNTs were found to have a strong ability in the adsorption of MCs. At the concentrations of 21.5 mg l À1 MC-RR and 9.6 mg l À1 MC-LR in 50 mmol phosphate buffer solution (pH 7.0), the adsorption amounts of MCs by CNTs with the range of outside diameter from 2 to 10 nm were 14.8 and 5.9 mg g À1 , which were about four times higher than those by other adsorbents tested. It was shown that with the decrease of CNTs outside diameters from 60 to 2 nm, the adsorption amount of MCs was apparently increased, however the size of CNTs particles formed in solution declined. This result implies that the size of CNTs tube pore that is fit for the molecular dimension of MCs plays a dominant role. Furthermore the specific surface area of CNTs was also found to be a factor in the adsorption of MCs. The results suggested that the selection of suitable size of CNTs as a kind of adsorbent is very important in the efficient eliminating MCs from drinking water in future.

Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes

“…It has been reported that CNTs functionalized with hydrophilic -OH and -COOH groups exhibited superior sorption for low molecular weight and polar compounds [18]. It has been also proposed that functionalized MWCNTs may provide an optimized approach for removal of target specific micropollutants [40]. However, our results revealed that the introduction of oxygencontaining functional groups decreased the adsorption capacity of MWCNTs for atrazine.…”

Evaluation of carbon nanotubes as a solid-phase extraction adsorbent for the extraction of cephalosporins antibiotics, sulfonamides and phenolic compounds from aqueous solution

“…The structure of CNTs resembles one (single-walled carbon nanotubes, SWCNTs) or more graphite sheets (multiwalled carbon nanotubes, MWCNTs) rolled up into a cylinder that consists of hexagon-rich sp 2 carbon at the wall and a few pentagons at the caps, getting more sp 3 -like as tube diameters become smaller (<0.7 nm) [11]. Because of the larger specific area and hydrophobic characteristic of the surface, CNTs have been regarded as a new kind of sorbent and have been studied for the removal of dioxin [12], trihalomethanes [13], microcystins [14], 1,2-dichlorobenzene [15], nicotine and tar [16]. They also showed satisfactory analytical potential as effective solid-phase extraction adsorbents for cyanazine [17], chlorotoluron [18], bisphenol A, 4-n-nonylphenol, 4-tert-octylphenol [19], chlorophenols [20], and several phthalate esters [21], non-steroidal anti-inflammatory drugs [22], and polybrominated diphenyl ethers [23].…”

Microcystin-LR biodegradation by Sphingopyxis sp. USTB-05

“…Aerobic biodegradation has been considered to be the main attenuation mechanism for MCs, and this process was reported to occur in diverse ecosystems, such as rivers [12], sand filters [11], reservoirs [20,21], coastal lagoons [22], lakes [17,23,24], and sewage effluent [25]. Bacterial strains of Sphingpoyxis sp.…”

“…The stable cyclic structure of MCs has presented many challenges to traditional water treatment technologies [16] where conventional processes, such as adsorption [17], ozone oxidation [18], photo-degradation [14], and electrochemical oxidation [19], have limited effect on their removal [11]. Aerobic biodegradation has been considered to be the main attenuation mechanism for MCs, and this process was reported to occur in diverse ecosystems, such as rivers [12], sand filters [11], reservoirs [20,21], coastal lagoons [22], lakes [17,23,24], and sewage effluent [25].…”