Synergistic effect of Thiourea and HCl on Palladium (II) recovery: An investigation on Chemical structures and thermodynamic stability via DFT

This work duly investigates the recovery of Pd (II) chlorocomplexes from industrial wastewater. Chemical structures and thermodynamic stabilities of the complex formed are evaluated via density functional theory (DFT). By applying synergistic solutions of thiourea mixed with hydrochloric acid (HCl), the stripping reaction of Pd (II) in the loaded Aliquat 336 occurs and Pd (II) chlorocomplexes coordinated thiourea ligands are formed, thus 80.19% of Pd (II) chlorocomplexes can be recovered. The aim of this study is to gain a better understanding of the stripping mechanisms and the structure of the complexes formed via the synergistic system. Such an understanding is still limited since little research has been conducted in this field. Owing to their molecular geometry, ligand coordination and donor groups play a vital role in the reactivity of palladium (II) complex. Quantum models have been developed to evaluate the chemical structure and thermodynamics stability of ((NH₂)₂CS·PdCl₂) namely: (i) DFT with B3LYP/6-31g(d,p) and MP2/6-31g(d,p) basis set, (ii) MP2 with cc-pVTZ basis set and (iii) CCSD(T)/cc-pVTZ. Results demonstrate that the highest geometric stability exhibited is the structure of Pd-S bonding with 180° Cl-Pd-Cl. The distance (r) and angle (a) of the selected geometrical parameters for (NH₂)₂CS·PdCl₂ complex are reported. Additionally, FTIR and UV–vis spectroscopies have been conducted to analyze the sampling solutions. Further, the calculated vibrational frequencies and experimental spectroscopic results show good agreement with the optimized geometry.     

Spent Grain from Malt Whisky: Assessment of the Phenolic Compounds

In order to extract antioxidant phenolic compounds from spent grain (SG) two extraction methods were studied: the ultrasound-assisted method (US) and the Ultra-Turrax method (high stirring rate) (UT). Liquid to solid ratios, solvent concentration, time, and temperature/stirring rate were optimized. Spent grain extracts were analyzed for their total phenol content (TPC) (0.62 to 1.76 mg GAE/g SG DW for Ultra-Turrax pretreatment, and 0.57 to 2.11 mg GAE/g SG DW for ultrasound-assisted pretreatment), total flavonoid content (TFC) (0.6 to 1.67 mg QE/g SG DW for UT, and 0.5 to 1.63 mg QE/g SG DW for US), and antioxidant activity was measured using 2,2-diphenyl-2-picrylhydrazyl (DPPH) free radical (25.88% to 79.58% for UT, and 27.49% to 78.30% for UT). TPC was greater at a high stirring rate and high exposure time up to a certain extent for the Ultra-Turrax method, and at a high temperature for the ultrasound-assisted method. P-coumaric acid (20.4 ± 1.72 mg/100 SG DW for UT, and 14.0 ± 1.14 mg/100 SG DW for US) accounted for the majority of the phenolic found compounds, followed by rosmarinic (6.5 ± 0.96 mg/100 SG DW for UT, and 4.0 ± 0.76 mg/100 SG DW for US), chlorogenic (5.4 ± 1.1 mg/100 SG DW for UT, and non-detectable for US), and vanillic acids (3.1 ± 0.8 mg/100 SG DW for UT, and 10.0 ± 1.03 mg/100 SG DW for US) were found in lower quantities. Protocatechuic (0.7 ± 0.05 mg/100 SG DW for UT, and non-detectable for US), 4-hydroxy benzoic (1.1 ± 0.06 mg/100 SG DW for UT, and non-detectable for US), and caffeic acids (0.7 ± 0.03 mg/100 SG DW for UT, and non-detectable for US) were present in very small amounts. Ultrasound-assisted and Ultra-Turrax pretreatments were demonstrated to be efficient methods to recover these value-added compounds.     

Theoretical study on the degradation mechanism of methamidophos and chloramine phosphorus with OH radicals

Theoretical investigation on the gas‐phase degradation reaction mechanism of methamidophos (MAP) and chloramine phosphorus (CHP) with OH radicals is performed. The equilibrium geometries and the harmonic vibration frequencies of the stationary points are obtained at M06‐2x/6‐31+G(d,p) level, and the higher‐level energetic information is further refined at M06‐2x/6–311++G(3df,2p) level. The rate constants for the 14 reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling correction over the temperature range 200–2000 K. The three‐parameter expressions of k₁(T) = 1.53 × 10^?19T^2.74exp(?1005.12/T), k₂(T) = 1.36 × 10^?20T^3.02exp(?1259.56/T) are given. The total rate constants of all reaction channels of MAP with OH radicals are in good agreement with the available experimental data. Our results indicate that the H‐abstraction reactions on methyl are the major channels for the reaction of MAP and CHP with OH radicals. © 2015 Wiley Periodicals, Inc.     

Dependency of dynamic interlaminar shear strength of composites on test technique used

Studies are presented on dependency of dynamic interlaminar shear (ILS) strength on the experimental technique used for a typical plain weave E-glass/epoxy composite. Dynamic ILS strength was determined based on two experimental techniques, namely torsional split Hopkinson bar (TSHB) apparatus using thin walled tubular specimens and compressive split Hopkinson pressure bar (SHPB) apparatus using single lap specimens. The results obtained from these techniques are compared. In general, it is observed that dynamic ILS strength for composites obtained by TSHB testing using thin walled tubular specimens is lower than the dynamic ILS strength obtained using single lap specimens in compressive SHPB. The issues involved in TSHB testing of thin walled tubular specimens made of composites are discussed and the reasons for reduced dynamic ILS strength using thin walled tubular specimens are highlighted. Finite element analysis (FEA) of thin walled tubular specimens made of composite and resin subjected to quasi-static torsional loading is presented. Using FEA results, the reasons for lower ILS strength of composite thin walled tubular specimens are substantiated.     

Synergistic effect of maleimido phenyl urea derivatives mixed with some commercial stabilizers on the efficiency of thermal stabilization of PVC

Four novel antimicrobial maleimido phenyl urea stabilizers 1–4 were synthesized from N-[4-(chlorocarbonyl) phenyl] maleimide with phenyl urea and its derivatives (p-methyl, o-chloro and p-carboxy). The effect of mixing maleimido phenyl urea stabilizer 2 with each of the reference stabilizers, dibasic lead carbonate (DBLC), cadmium-barium-zinc stearate (Cd-Ba-Zn stearate) or n-octyltin mercaptide (n-OTM), on the stabilization efficiency in thermal degradation of rigid PVC at 180 °C in air, has been investigated. Mixing was effected in the range of 0–100 wt% of stabilizer 2 relative to each of the reference stabilizers. The stabilizing efficiency was evaluated by measuring the length of the thermal stability period (Ts), the period during which no detectable amount of hydrogen chloride gas could be observed, and also from the rate of dehydrochlorination as measured by continuous potentiometric determination, and by the extent of discoloration of the degraded polymer samples. The results show a true synergistic effect from the combination of stabilizer 2 with any of the reference stabilizers. Mixing of the stabilizers improves the Ts values, decreases the rate of dehydrochlorination and lowers the extent of discoloration of the polymer. The maximum synergism was attained when stabilizer 2 is mixed with either of the three reference stabilizers in equivalent weight ratio (50%/50%). The observed synergism may be attributed to the different mechanisms by which the investigated and the reference stabilizers work.     

Missing value imputation strategies for metabolomics data

The origin of missing values can be caused by different reasons and depending on these origins missing values should be considered differently and dealt with in different ways. In this research, four methods of imputation have been compared with respect to revealing their effects on the normality and variance of data, on statistical significance and on the approximation of a suitable threshold to accept missing data as truly missing. Additionally, the effects of different strategies for controlling familywise error rate or false discovery and how they work with the different strategies for missing value imputation have been evaluated. Missing values were found to affect normality and variance of data and k‐means nearest neighbour imputation was the best method tested for restoring this. Bonferroni correction was the best method for maximizing true positives and minimizing false positives and it was observed that as low as 40% missing data could be truly missing. The range between 40 and 70% missing values was defined as a “gray area” and therefore a strategy has been proposed that provides a balance between the optimal imputation strategy that was k‐means nearest neighbor and the best approximation of positioning real zeros.     

The free retraction of natural rubber: A momentum-based model

The free retraction of vulcanised strips of natural rubber released from simple uniaxial deformation is studied using high speed cinematography in the context of a simple momentum theory. Good agreement between the theory and experiment is observed when vulcanisates are released from stresses below 1 MPa, which corresponds to tensile strains rates below 1 × 10³ s⁻¹. Above this critical stress and corresponding strain rate value, an increasing dispersion is observed in the form of slowing down of the characteristic retraction pulse, and also by a relaxation of strain ahead of the pulse front (a dispersion of the pulse). Holding samples at high strains for an extended period of time prior to releasing results in a further, significant retardation of the retraction pulse velocity. These effects are related to the increasing non-linearity of high strain rate retraction stress–strain behaviour. Energy balance arguments show that the dispersion of the retraction pulse is a prerequisite for pulse propagation, and that its magnitude underpins the deviation from the momentum model outlined in this paper.     

环烷酸对油水界面膜流变性质的影响研究

研究了环烷酸对油水界面膜界面张力、弹性模量、损耗模量以及界面膜破裂速率常数的影响,同时对环烷酸与沥青质之间的相互作用进行了测定。结果表明,环烷酸使得原油油水界面张力下降;弹性模量随着环烷酸加量以及振荡频率的增加都分别逐渐增大,并且最终都趋于平衡;在任何振荡频率值时,损耗模量都随着环烷酸加量先增大后减小;当环烷酸加量增加时,界面膜破裂速率常数降低。环烷酸与沥青质之间存在相互作用,随着环烷酸加量的增加,其对沥青质界面膜弹性模量的影响与对原油界面膜弹性模量的影响相似,表明环烷酸主要是通过与沥青质相互作用而促进乳状液稳定性的。     

气基磁化焙烧回收包头稀土尾矿中铁的研究

试验采用磁化焙烧-磁选的方法来回收包头稀土尾矿中的Fe。考察了还原球团的粒径、焙烧温度、还原气体的成分、还原气气体流量、焙烧时间对于磁化焙烧回收Fe的影响。在焙烧温度为580℃,CO与CO2的浓度比为40∶60,还原气体气流量为1.2 L·min-1,焙烧时间为60 min的条件下对球团进行磁化焙烧,并将焙烧后的球团进行磨矿,使得-200目的物料占物料总重量的95%。将磨矿后的物料置于磁场强度为233 k A·m-1的磁选管中进行磁选,可以得到品位为60%左右的铁精矿,其铁回收率达到70%左右。