Dechelation of Cd-EDTA complex and recovery of EDTA from simulated soil-washing solution with sodium sulfide.

Washing water containing poorly degradable heavy metal-EDTA complexes is produced by ethylenediaminetetraacetic acid (EDTA) washing of heavy metal-contaminated soil. A series of batch experiments were performed to explore the dechelation of heavy metal-EDTA complexes and the recovery of EDTA from simulated soil-washing solution using sulfide precipitation with Na2S. The results showed that the effect of Na2S dosage on the dechelation of Cd-EDTA solution was greater than that of other factors (reaction temperature, time, and pH) and excess EDTA suppressed cadmium removal. Additionally, the Cd removal efficiency reached 99.99 ±â€¯0.001%, and the residual amount of Cd-EDTA was below the detection limit of ion chromatography (IC) measurements under the following optimal conditions: an initial Cd-EDTA solution pH of 6, a sodium sulfide-to-Cd-EDTA ratio of 2:1, a reaction temperature of 25 °C, and a contact time of 20 min. Furthermore, the results of analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES), Fourier transform infrared (FT-IR) spectroscopy, and ion chromatography (IC) confirmed that the dechelation process could be completed in less than 20 min and that EDTA was completely recovered as trisodium EDTA (HNa3EDTA). The mechanism for the dechelation of Cd-EDTA and recovery of EDTA using sulfide precipitation with Na2S was also proposed. The recovered EDTA with acidification had the same ability to extract heavy metals from soil with fresh EDTA. This study may facilitate the recycling of soil-washing wastewater and reduce the cost of extracting heavy metals from soil using EDTA.

Effects of carrier on the transport and DDT removal performance of nano-zerovalent iron in packed sands.

The delivery of nano-zerovalent iron (nZVI) as a remediation agent to targeted areas in soil was studied using different carriers. Among water, surfactant solution, and surfactant foam, the nZVI transport and carrying abilities followed the order of surfactant foam > surfactant solution > water. The nZVI migration was also facilitated by increased soil particle size and high surfactant concentration. Batch experiments probed the remediation of dichlorodiphenyltrichloroethane (DDT)-contaminated sand under different conditions. Compared to surfactant solution, the use of foam as a carrier achieved much higher DDT removal efficiencies for both coarse (foam/solution: 99/69%) and fine (foam/solution: 60/26%) sands. Additionally, the DDT removal efficiency was strongly influenced by surfactant concentration: foams generated using 1 and 5 g L-1 sodium lauryl ether sulfate (SLES) solutions reached the respective efficiencies of 44% and 75% under identical experimental conditions. However, the nature of the surfactant did not significantly affect the total removal efficiency of DDT. Solubilization, increased sweep efficiency, and reduction by nZVI were identified as factors affecting the DDT removal efficiency, and all three of them were involved when foam-nZVI was used as the flushing fluid.

The principle and effect of transfer agent for the removal of PCE during in situ chemical oxidation.

Viscosity remedial technology, which uses a water-soluble polymer mixed with remedial fluids, has been introduced in recent years to improve the removal efficacy of perchloroethylene/tetrachloroethylene (PCE) by improving oxidant coverage (i.e. sweep efficiency). Xanthan gum and hydrolysed polyacrylamide (HPAM) are relatively stable with time and temperature and possess salt and oxidation resistance, indicating that they may be good flooding agents (the former is better than the latter in this work). In this work, we quantified the polymer directly improved oxidation of PCE during transport by using a two-dimensional flow tank. Using a low pore volume (≤3.0), the removal rate of the PCE increased with the polymer concentration before stabilizing at approximately 93.00 and 88.30% for xanthan and HPAM, respectively. In this work, over 80% of PCE was removed via less than 3.0 PV of the SDS solution, whereas complete removal (100%) was achieved with less than 3.0 PV of SDS foam. Furthermore, the new experimental discoveries demonstrate that xanthan is better than HPAM and SDS foam is a better remediation agent than the SDS solution for removing PCE. Graphical abstract (Reaction device, A - inlet device (pump 1#), B - 2D tank, C - outflow device (pump 2#), D - data recording and processing device, E - microscopic expression, E (a) - KMnO4 flushing, E (b) - polymer solution flushing).

Design, synthesis, and evaluation of 7H-thiazolo-[3,2-b]-1,2,4-triazin-7-one derivatives as dual binding site acetylcholinesterase inhibitors.

New dual binding site acetylcholinesterase (AChE) inhibitors have been designed and synthesized as a new drug candidate for the treatment of Alzheimer's disease (AD) through the binding to both catalytic and peripheral sites of the enzyme. Therefore, a series of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives 6a-j were synthesized and investigated for their ability to inhibit the activity of human AChE (hAChE) in comparison with huperzine-A. All the compounds were found to inhibit AChE activity, especially compounds 6c and 6i with the inhibition value of 76.10% and 77.82%, respectively. The molecular docking study indicated that they were nicely accommodated by AChE. The molecular docking study revealed that 6c and 6i possessed a more optimal binding conformation than 6a and can perfectly fit into the active and peripheral site of hAChE, and consequently exhibited highly improved inhibitor potency to hAChE.

Synthesis and biological evaluation of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives as dual binding site acetylcholinesterase inhibitors.

A series of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives 7a-i were synthesized and evaluated as novel acetylcholinesterase (AChE) inhibitors. All target compounds were evaluated in vitro for the inhibitory activities against AChE via Ellman colorimetric assay. Compound 7c showed an excellent (89.82%) inhibitory activity. The molecular docking studies revealed that 7c, 7d and 7g, with the lateral chain in the para position of the phenyl ring, possessed an optimal docking pose and can perfectly fit into the catalytic active site (CAS) and peripheral anionic site (PAS), simultaneously, and, consequently, exhibited higher inhibitory potency than 7b that bears the same lateral chain as 7g, but in the ortho position of the phenyl ring.

Ultrasound-mediated synthesis of N,N-bis(phenacyl)aniline under solvent-free conditions.

ABSTRACT: An efficient method for the synthesis of N,N-bis(phenacyl)anilines was developed via smooth condensation of anilines with α-bromoacetophenones in the presence of sodium carbonate as acid acceptor and polyethylene glycol 400 (PEG 400) as catalyst at room temperature under solvent-free conditions by using 350 W ultrasound irradiation. In addition to experimental simplicity, the main advantages of the procedure are mild conditions, short reaction times (30-45 min), and high yields (73-83 %).