Degradation of bisphenol A through transition metals activating persulfate process.

In this study, the process of transition metals (Fe2+, Fe0, Ni2O3) activating persulfate was attempted to degrade aqueous bisphonel A (BPA). Compared with thermal activation mode, significant degradation can be achieved at normal atmospheric temperature in transition metal activation mode. BPA removal in the transition metal-PS system can be divided into rapid phase (0-5 min) and slow phase (5-60 min). In rapid phase, 87.71% and 90.60% removal efficiencies were obtained in the Fe2+-PS and Ni2O3-PS systems, and the contaminant was almost completely oxidized after 60 min. There are many similarities between the Fe2+-PS and Fe0-PS systems, in particular the optimal removal efficiencies were achieved at n0(Fe2+):n0(PS) = 1:2 and n0(Fe0):n0(PS) = 1:2 rather than with maximum metal dosage. The Ni2O3 dosage had positive correlation with BPA removal rate while the degradation efficiency of the Fe2+-PS system could be promoted by keeping n0(sodium citrate):n0(Fe2+) below 1:1. Intermediate products of the Fe2+-PS system were analyzed by LC-MS and were predominantly phenol, p-hydroxyacetophenone, benzoquinone and propanedioic acid, therefore a possible oxidation degradation pathway was speculated.

Dithiocarbamate-modified starch derivatives with high heavy metal adsorption performance.

In this work, three types of dithiocarbamate (DTC)-modified starch derivatives including DTC starch (DTCS), DTC enzymolysis starch (DTCES) and DTC mesoporous starch (DTCMS) were developed, which showed the significant heavy metal adsorption performance. The adsorption ability of these three DTC modified starch derivatives followed the sequences: DTCMS>DTCES>DTCS. In single metal aqueous solutions, the uptake amount of heavy metal ions onto the modified starches obeyed the orders: Cu(II)>Ni(II)>Cr(VI)>Zn(II)>Pb(II). The adsorption mechanism was proved by the chelating between DTC groups and heavy metal ions through the pH effect measurements. A monolayer adsorption of Langmuir isotherm model for the adsorption of Cu(II) onto DTCMS was well fitted rather than the multilayer adsorption of Freundlich isotherm model. The adsorption kinetics of Cu(II) onto starch derivatives was found to be fit well with the pseudo-second-order model. Additionally, in the presence of EDTA, the adsorption ability and uptake amount of heavy metal ions onto these three DTC modified starch derivatives is identical with the results obtained in the absence of EDTA.

Synthesis and adsorption performance of dithiocarbamate-modified glycidyl methacrylate starch.

The design of chelating polymers with fast complexation of the metal ions is particularly interest. In this work, the dithiocarbamate-modified glycidyl methacrylate starch was synthesized and characterized by FT-IR, (13)C NMR and XRD spectra. Its sorption performance for heavy metals fixation was studied. It was found that the removal process of metal ions involved a fast increase stage followed by a slower stage. There was a higher match between the pseudo-second-order equation and the experimental data. The sorption rate constants were related to the substitution rates of hydrated metal ions in aqueous solutions, showing typical chemisorption. The Langmuir isotherm gave satisfying fits to equilibrium data of metals adsorption. And the capacities followed the sequence Cu(2+)>Cd(2+)>Co(2+)>Zn(2+)>Ni(2+)>Mn(2+), which could be well demonstrated with chelating interaction caused by sulfur atoms. Such understanding provides new insights as how to synthesize and use the dithiocarbamate-based polysaccharides.

Application of dithiocarbamate-modified starch for dyes removal from aqueous solutions.

The present study shows that the dithiocarbamate-modified starch (DTCS) is a commercially promising sorbent for the removal of anionic dyes from aqueous solutions. It is more effective than activated carbon for this purpose. At the appropriate solution pH of 4, kinetic studies indicate that the sorption of the dyes tends to follow pseudo-first-order equation. The sorption equilibrium is best described by the Langmuir-Freundlich isotherm model at 298 K. The capacities for individual dyes follow the sequence acid orange 7 > acid orange 10 > acid red 18 > acid black 1 > acid green 25, which is consistent with the inverse order of molecular size. The negative enthalpy change for the adsorption process confirms the exothermic nature of adsorption, and a free energy change confirms the spontaneity of the process. The FT-IR spectra and thermogravimetric analyses verify the sorption based on starch-NH(2)(+)CSSH⋯(-)O(3)S-dye electrostatic attraction. The DTCS can be regenerated from the dye loaded DTCS in a weak basic solution containing sodium sulfate.

Behaviors and mechanism of acid dyes sorption onto diethylenetriamine-modified native and enzymatic hydrolysis starch.

In this paper, different starches were modified by diethylenetriamine. The native starch reacted with diethylenetriamine giving CAS, whereas the enzymatic hydrolysis starch was modified by diethylenetriamine producing CAES. Adsorption capacities of CAES for four acid dyes, namely, Acid orange 7 (AO7), Acid orange 10 (AO10), Acid green 25 (AG25) and Acid red 18 (AR18) have been determined to be 2.521, 1.242, 1.798 and 1.570 mmol g(-1), respectively. In all cases, CAES has exhibited higher sorption ability than CAS, and the increment for these dyes took the sequence of AO7 (0.944 mmol g(-1))>AO10 (0.592 mmol g(-1))>AR18 (0.411 mmol g(-1))>AG25 (0.047 mmol g(-1)). Sorption kinetics and isotherms analysis showed that these sorption processes were better fitted to pseudo-second-order equation and Langmuir equation. Chemical sorption mechanisms were confirmed by studying the effects of pH, ionic strength and hydrogen bonding. Thermodynamic parameters of these dyes onto CAES and CAS were also observed and it indicated that these sorption processes were exothermic and spontaneous in nature.

Equilibrium and molecular mechanism of anionic dyes adsorption onto copper(II) complex of dithiocarbamate-modified starch.

The assembly of dyes molecules on metal-polymer complexes is of interest due to their potential applications in photovoltaic cell, separation, and wastewater treatment. In the present work, the interaction of anionic dyes (acid orange 7, acid orange 10, acid green 25, and acid red 18) with the copper(II) complex of dithiocarbamate-modified starch (DTCSCu) was investigated. The sorption studies showed that the interaction mechanism was based on chelating adsorption. The equilibrium data fitted well with Langmuir-Freundlich isotherm, and the capacities followed the order AO7 > AG25 > AR18 > AO10. It was affected by the structure of the dye. The sulfonate groups located on benzene rings favored efficient adsorption. Despite the difference in capacity, the molar n(dye):n(Cu) ratios for acid orange 10, acid red 18, and acid green 25 were approximately 1:2 when the maximum capacities for the dyes were achieved at the optimal pH of 4. It suggested that one dye molecule bound to one dinuclear copper center on DTCSCu. The molar n(dye):n(Cu) ratio for the smallest dye, acid orange 7 (AO7), approached 1:1, demonstrating two AO7 molecules binding to two copper ions of the dinuclear core. The dyes adsorption related to the dinuclear copper core available on the polymer was further verified by electron spin resonance studies. Such interaction resulted in the formation of a ternary dye-metal-polymer complex. The ternary complexes were more stable than DTCSCu, which favored the adsorptions.

Ethylenediamine modified starch as biosorbent for acid dyes.

This work investigated the sorption performance of the ethylenediamine modified starch (CAS) for the removal of acid dyes from aqueous solutions. The influence of pH on adsorption of acid orange 10 (AO10), acid green 25 (AG25) and amido black 10B (AB10B) was evaluated. The sorption kinetics, equilibrium uptake and desorption of the loaded dyes in sodium sulfate solution were studied. It was found that the interaction mechanism was based on electrostatic attraction and hydrogen bonding. The adsorption of AG25 and AB10B followed pseudo-second-order model, whereas AO10 followed both pseudo-first-order and pseudo-second-order models. The best isotherm was Langmuir equation and the capacities followed the sequence AB10B>AG25>AO10. The different behaviors of individual dyes adsorption on CAS were largely dependent on the number of hydrophilic functional groups, which had strong tendency to form hydrogen bonds with the biosorbent. Dye release in sodium sulfate solutions was determined by the salt concentration and nature of dyes.

[Spectra study of a sodion triethylenetetramine-bisdithiocarbamate and its complexes with heavy metal ions].

A sodion triethylenetetramine-bisdithiocarbamate (DTC-TETA) and its complexes with heavy metal ions were investigated by FTIR, UV, FAAS and elemental analysis, respectively. The FTIR spectrum of DTC-TETA showed strong absorption peaks at 1 461-1 388 cm(-1) and 1 174-996 cm(-1) which were attributed to partly double bonds of C-N and C-S, respectively. The UV spectrum of DTC-TETA had two absorption peaks at 265 and 290 nm, assigned to pi-pi* transition of N...C...S radical and nonbonding electron n-pi* transition of S...C...S radical to conjugated system, respectively. The elemental analysis results demonstrated that the mol ratio of C, H, N and S in DTC-TETA was about 2 : 4 : 1 : 1. As for UV spectrum of its complexes with Cu(II), Cd(II), Zn(II) and Ni(II), there were four new absorption peaks at 321, 310, 311 and 325 nm, respectively. Coupled to flow-injection, FAAS determination showed that the complexation performance of Cu2+, Cd2+, Ni2+ and Zn2+ complexes of DTC-TETA was better than that of sodium diethyldithiocarbamate (DDTC).

[Spectra characteristics of an aminated glucose and its complex with Cu(II)].

Characteristics of an aminated glucose and its complex with Cu (II) were investigated by FTIR, 1H-NMR and UV spectroscopy, respectively. Compared with glucose, the FTIR spectrum of an aminated glucose showed a moderate peak at 1 629-1 608 cm(-1) which was attributed to deltaNH vibration, suggesting that glucose reacted with ethylenediamine. The 1H-NMR spectrum of an aminated glucose demonstrated the signal of the C1 hydroxy proton and one of the amino proton at 4. 82-4. 79 ppm, illustrating that the amino of ethylenediamine was substituted for the hydroxy group of C1. As for UV spectra, an aminated glucose did not show absorbance in the ultraviolet region while its complex with Cu(II) had obvious absorption peak at about 236 nm. The complex ratio of the aminated glucose to Cu(II) was about 1 to 1 and the stability constant of its Cu(II) complex was 6.8 x 10(7) L x mol(-1).

Aniline degradation by electrocatalytic oxidation.

The degradation of aniline solution in alkaline medium of pH 11.0 by electrocatalytic oxidation has been studied using an electrochemical reactor containing a SnO(2)-Sb(2)O(3)-PtO anode and a Ti cathode, both of 54 cm(2) area. Hydroxyl radicals (HO(z.rad;)) are produced at the anode, being tested with the trace catcher salicylic acid and phenol by spectrophotometery and high performance liquid chromatography. Intermediates dianiline, 4-anilino phenol and azobenzol were detected by gas chromatography-mass spectrometry. The existence of HO(z.rad;) produced in the aniline degradation was assayed with scavenger tertiary butanol. The results showed that electrocatalytic oxidation is an effective process for the degradation of aniline. A general reaction pathway that accounts for aniline degradation to CO(2) involving those intermediates is proposed.