EXAFS and XANES Studies of Retention of Copper and Lead by a Lignocellulosic Biomaterial

Liu

et al. 2006

Planta

The uptake and bioavailability of lead (Pb) in soil-plant systems remain poorly understood. This study indicates that acetic and malic acids enhance the uptake of Pb by wheat (Triticum aestivum L.) roots under hydroponic conditions. The net concentration-dependent uptake influx of Pb in the presence and absence of organic acids was characterized by Michaelis-Menten type nonsaturating kinetic curves that could be resolved into linear and saturable components. Fitted maximum uptake rates (V max ) of the Michaelis-Menton saturable component in the presence of acetic and malic acids were, respectively, 2.45 and 1.63 times those of the control, while the Michaelis-Menten K m values of 5.5, 3.7 and 2.2 lM, respectively, remained unchanged. Enhanced Pb uptake by organic acids was partially mediated by Ca 2+ and K + channels, and also depended upon the physiological function of the plasma membrane P-type ATPase. Uptake may have been further enhanced by an effectively thinner unstirred layer of Pb adjacent to the roots, leading to more rapid diffusion towards roots. X-ray absorption spectroscopic studies provided evidence that the coordination environment of Pb in wheat roots was similar to that of Pb(CH 3 COO) 2 Á3H 2 O in that one Pb atom was coordinated to four oxygen atoms via the carboxylate group.

Section: Discussionsupporting

confidence: 84%

Organic acids enhance the uptake of lead by wheat roots

Wang

Liu

et al. 2006

Planta

“…6a, the fitting of this peak leads to 1.8 oxygen atoms at 2.37 Å for peat and 1.8 oxygen atoms at 2.39 Å for soil (Table 4). This result is similar to lead sorption studies reported by Dupont et al (2002) and Rouff et al (2004). As expected, the coordination number is particularly low because of high structural disorder of Pb coordination shell.…”

Section: X-ray Absorption Measurementssupporting

confidence: 91%

Effect of lead on the sorption of 2,4,6-trichlorophenol on soil and peat

Pei

Environmental Pollution

Liu

et al. 2007

Lead diminished the sorption of 2,4,6-trichlorophenol onto soil and peat. AbstractThe effect of lead on the sorption of 2,4,6-trichlorophenol (2,4,6-TCP) on soil and peat was investigated using a batch equilibration method. Lead markedly diminished the sorption of 2,4,6-TCP, and 2,4,6-TCP had little effect on lead sorption. Peat was a more effective adsorbent for 2,4,6-TCP than soil. The desorption hysteresis of 2,4,6-TCP verified the presence of high-energy sorption sites. Mechanisms of lead suppression effect on the 2,4,6-TCP sorption included the following: Firstly, lead accelerated the aggregation of colloids, the aggregates covered the surface in part and shrunk the pore sizes of the adsorbents, hence decreased the sorption of 2,4,6-TCP. Secondly, X-ray absorption and Fourier transform infrared spectroscopy study suggested that lead competed with 2,4,6-TCP for carboxylic, phenolic and Si-OH groups of organic matter and clay minerals. Such competition was partly responsible for the overall suppression effect of lead on the sorption of 2,4,6-TCP.

“…The fitting of this peak leads to 1.8 oxygen atoms at 2.38Å for Pb 2+ -MWCNTs-O(7.58%) and 1.8 oxygen atoms at 2.37Å for Pb 2+ -MWCNTs-O(2.66%). These results are similar to that of Dupont et al [43]. The coordination number was particularly low as expected because of the highly structural disorder of Pb coordination shells.…”

Section: Xas Analysissupporting

confidence: 92%

Adsorption of diuron and dichlobenil on multiwalled carbon nanotubes as affected by lead

Chen

Journal of Hazardous Materials

Pei

et al. 2011

a b s t r a c tThe effect of lead on the adsorption of diuron and dichlobenil on multiwalled carbon nanotubes (MWCNTs) was investigated to explore the possible application of MWCNTs for removal of both herbicides from contaminated water. The adsorption of diuron and dichlobenil on MWCNTs at pH 6 was nonlinear and fit the Polanyi-Manes model well. The adsorption of diuron and dichlobenil was closely correlated with specific surface areas and micropore volumes of MWCNTs. An increase in oxygen content of MWCNTs with same diameters and similar surface areas decreased the adsorption of diuron and dichlobenil, while increased the adsorption of lead. Micro-Fourier transform infrared spectroscopic study indicated that hydrogen bonding is a main mechanism responsible for the adsorption of diuron or dichlobenil onto MWCNTs-O. Oxygen containing groups, mainly carboxylic groups, significantly increased the adsorption of lead through the formations of outer-sphere and inner-sphere complexes, which are verified by X-ray absorption spectroscopic measurements. Oxygen containing groups and the presence of lead diminished the adsorption of diuron and dichlobenil. The suppression mechanisms of lead were ascribed to hydration and complexation of lead with carboxylic groups, which may occupy part of surface of MWCNTs-O. The large hydration shell of lead cations may intrude or shield hydrophobic and hydrophilic sites, resulting in a decreased adsorption of diuron and dichlobenil at the lead-complexed moieties.