Search

Abstract Immobilization has been regarded as one of the most effective technology to eliminate heavy metals contamination. However, the stability of immobilization products and the leakage of immobilized heavy metals impeded its further application. In order to depict the stability of chelating complexes C 10 H 20 MnN 2 S 4 , C 10 H 20 CuN 2 S 4 and C 10 H 20 ZnN 2 S 4 , DSC-TG analysis, DFT calculation and leakage tests were carried out to reveal the stabilities and the potential leakage risks of immobilized heavy metals when sodium diethyl dithiocarbamate was used as soil amendments. The results indicated that the stability of these three chelating complexes was ranked in the order of C 10 H 20 CuN 2 S 4 > C 10 H 20 ZnN 2 S 4 > C 10 H 20 MnN 2 S 4. Such precipitations as C 10 H 20 MnN 2 S 4 , C 10 H 20 CuN 2 S 4 and C 10 H 20 ZnN 2 S 4 were stable under the neutral and alkaline environment. Meanwhile, leakage of immobilized heavy metals decreased with the increasing leaching pH, whereas time and temperature had no significant impact on the leakage of immobilized heavy metals. And the maximum leakage of immobilized heavy metals was lower than the limited concentration. Graphical abstract Image 103056 Highlights • DDTCNa was used to immobilize heavy metal ions (Mn, Cu and Zn). • Stability of chelating complexes decreased in the order of C 10 H 20 CuN 2 S 4 > C 10 H 20 ZnN 2 S 4 > C 10 H 20 MnN 2 S 4. • The maximum leakage concentration of heavy metal ions was lower than the limited standard concertation. [ABSTRACT FROM AUTHOR]

Diffusive gradients in thin films (DGT) have been tested in CO2-rich, metal-bearing fluids from springs in the Campo de Calatrava region in Central Spain, to assess their applicability as a monitoring tool in onshore CO2 storage projects. These films are capable of adsorbing metals and recording changes in their concentration in water, sediments, and soils. Considering that CO2 dissolution promotes metal solubilization and transport, the use of these films could be valuable as a monitoring tool of early leakage. A number of DGT have been deployed in selected springs with constant metal concentration. The studied waters show high concentrations of Fe, as high as 1 × 104 μg·L−1, Ni, Co, Zn, Cu, and Mn. Comparing re-calculated metal concentration in DGT with metal water concentration, two different metal behaviors are observed: (i) metals with sorption consistent with the metal concentration (i.e. plotting close to the 1:1 line in a [Me]DGT: [Me]water plot), and (ii) metals with non−linear sorption, with some data showing metal enrichment in DGT compared with the concentration in water. Metals in the first group include Fe, Mn, Co, Ni, and U, and metals in the second group are Zn, Pb, Cr, Cu, and Al. From this research, it is concluded that the metals in the first group can be used to monitor potential leakage by using DGT, providing effective leakage detection even considering low variations of concentrations, episodic metal release, and reducing costs compared with conventional, periodic water sampling. [ABSTRACT FROM AUTHOR]

Abstract: The recovery of H2SO4 from waste anodic aluminum oxidation solution using diffusion dialysis process was investigated by a series of batch, dynamic and pilot-scale tests. Experimental results from batch tests indicated that to some extent agitation could reduce concentration polarization phenomenon and CuSO4 could enhance proton permeability throughout the DF120 anion exchange membrane. Dynamic experimental results showed that both acid recovery and H+ concentration in recovered acid decreased with flow rate increase when the flow rate ratio of water to feed was kept at 1.0, and the optimal flow rate range of 3.0×10−4 m3/h to 5.0×10−4 m3/h (corresponding to the membrane flux of 9.4×10−5 m3/hm2 to 1.56×10−4 m3/hm2) was obtained. Although acid recovery efficiency could be improved by increasing the flow rate ratio, the recovered acid concentration decreased and metal leakage increased. And it is confirmed that the optimal flow rate ratio of water to feed should be controlled at 1.0–1.2. Pilot-scale tests performed very well when using the wastewater from a real anodic aluminum oxidation plant. H2SO4 recovery, recovered acid concentration and Al3+ leakage in steady-state condition were 85.25%, 4.08mol/L and 4.98%, respectively, suggesting that diffusion dialysis is a cost-effective technique for acid recovery from waste anodic aluminum oxidation solution. [Copyright &y& Elsevier]

Electric field (EF) variables and electrode material are fundamental factors in ohmic heating (OH) processing. In this study, stainless steel, titanium and graphite were used as electrodes in conventional and OH (at 50 Hz and 20 kHz) treatments of whey protein isolate solutions at pH 3 and pH 7. The treated solutions were characterized in terms of UV absorbance, changes in intrinsic fluorescence, binding of a conformational probe and secondary structure (evaluated by circular dichroism). Differentiated structural features were induced by the different treatment conditions and were more evident at pH 7 and OH at 50 Hz. The metal leakage (quantified with ICP-MS) from the electrodes revealed to influence the equilibrium of early stages of protein aggregation, with stainless steel demonstrating to be the most electro-active material followed by titanium and finally graphite (that did not release metal). These findings highlight that structural properties of whey proteins may not only be influenced by the EF action but also by the leakage of metals from the electrodes. OH is a recognized emerging processing technology and has a recognized potential to control and enhance protein functionality due its ability to influence protein structural features. Both electrode stability and protein structural changes are related with the EF operational parameters such as voltage, current or frequency. These parameters are decisive in the occurrence and extension of electrochemical phenomena and in the EF action mechanisms over protein structure. The confirmation of EF non-thermal effects at high and low frequencies (independently of the electrochemical phenomena) dissipated previous doubts regarding its effectiveness to modulate protein functionality. The understanding of the electrode material stability and influence of different electric parameters on the product's functionality, stability and safety are fundamental to design OH devices and to the establishment of operational protocols. The stability and material release from the electrodes is a fundamental factor during OH processing, imposing serious implications in equipment costs, maintenance, as well as in product quality and safety. This study highlights the influence of different electrode materials during OH at different electrical frequencies and its impacts on protein structural aspects. • Electric frequency and electrochemical reactions were evaluated during OH. • Metal release was quantified in OH and conventional heating. • EF-related effects were verified on OH treated samples. • Protein structure was affected by EF action during OH. • Protein aggregation was influenced by the metal released from the electrodes. [ABSTRACT FROM AUTHOR]