Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of p H and fluoride at different molar ratios of fluoride to Al(R F:Al) on the removal of cadmium(Cd~(2+)) and phosphate by Al coagulation. Fluoride at R F:Al≥ 3:1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R F:Al of 10:1 whereas at lowered R F:Al(i.e., ≤ 6:1), an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at p H 7 and 8 and that of phosphate at p H 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R F:Al. The Al fluoride interactions include the formation of Al–F complexes and the adsorption of fluoride onto Al(OH)_3 precipitates, i.e., the formation of Al(OH)n F m. Al–F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower p H. Al–F complexes at high R F:Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R F:Al shows little effect on Al coagulation behavior towards Cd~(2+)and phosphate, and the spent defluoridation adsorbent,i.e., aluminum(Al) hydro(oxide) with adsorbed fluoride at R F:Al of below 0.1:1, may be reclaimed as a coagulant after being dissolved.     

铜、锌氰配合物在离子交换纤维上的扩散、吸附机理

运用Boyd液膜扩散公式和范山鹰等提出的扩散模型,考察了碱性溶液中铜、锌氰配合物在离子交换纤维上的扩散行为;通过分析吸附前后纤维上官能团的位置变化以及解吸前后纤维上元素含量的变化,研究铜、锌氰配合物在纤维上的吸附机理。实验结果表明,离子交换纤维对铜、锌配合物的吸附在反应初期,以液膜扩散为主控制步骤,反应后期,以空隙扩散为主控制步骤。并运用离子交换纤维在水溶液中具有类似胶体型物质的双电层结构解释了不同控制阶段吸附速率不同的原因,虽然各阶段吸附速率有所不同,但纤维对铜、锌氰配合物的吸附均为离子交换机制。     

Selective metal leaching from technosols based on synthetic root exudate composition

This study focused on metal release from technosols induced by synthetic root exudate (SRE). The effect of SRE composition on metal release was studied using six technosols. This was done by treating the technosols with SRE solutions having varying concentrations of low molecular weight organic acids (LMWOAs), namely oxalic, citric, and malic acids. Consequently, the physico-chemical parameters (pH and electric conductivity), Ca, Mg, Fe, Zn, and Cu release (by atomic absorption spectroscopy, AAS), chemical changes (by Fourier transform infrared, FT-IR), and organic parameters (by fluorescence) were investigated. Metal release showed to be dependent on the SRE composition and technosol characteristics. Citric acid selectively released Ca, Mg, Zn, and Cu from technosols in a concentration-dependent manner; oxalic acid showed a significant role in the release of Mg and Fe. Under relatively high LMWOA concentrations, particulate organo-mineral complexes precipitated. Additionally, technosol weathering was seen by the dissolution of humic substances and ferriallophanes, which in turn caused metal release. However, re-precipitation of these phases showed to re-sorb metals, thus underestimating the role of LMWOAs in metal release. Therefore, the selective metal leaching was highly dependent on the SRE composition and LMWOA concentrations on one hand, and on the mineral, organic, and organo-mineral components of the technosols on the other. The understanding of such processes is crucial for proposing and implementing environmental management strategies to reduce metal leaching or for the beneficial re-usage of metals (e.g., for agromining) from technosols.     

Biodegradable Complex Polymers from Casein and Potato Starch

Potato starch was blended with defatted milk in proportions providing a 4:1, 3:1, 2:1, 1:1, 1,:2, 1:3, and 1:4 starch/casein ratio. Precipitation was achieved by addition of either hydrochloric acid or leaven. Composition of precipitated products was determined based on elemental analysis for nitrogen. Generally, differences between attempted and achieved casein-to-starch proportions did not exceed 10%. Products coprecipitated with hydrochloric acid were slightly richer in casein than products obtained with leaven. Aqueous solubility, water binding capacity, IR spectra, and thermal analysis (thermogravimetry, TG, and differential thermogravimetry, DTG) were recorded for the precipitates. Analyses revealed that the precipitates were not simple physical mixtures of the components. Partial insolubility in 7 M aqueous urea showed that casein and potato starch are chemically bound. Comparison of the spectra and thermograms suggested that complexes of the 1:1 composition were formed constituting a nucleus of the aggregates carrying excessive amounts of either starch or casein.     

Fluorescence studies of dye displacement from DNA by chromium(III) complexes: Evidence for cation induced DNA condensations

The interactions of 10 different chromium(III) complexes with isolated calf thymus DNA have been analysed by studying the electronic and fluoresence spectra of intercalated ethidiumbromide. Triply charged cationic complexes including: [Cr(urea)₆]Cl₃.3H₂O, [Cr(1,10‐phenanthroline)₃](ClO₄)₃.2H₂O, [Cr(2,2'‐bipyridyl)₃] (ClO₄)₃.2H₂O, [Cr(ethylendiamine)₃]Cl₃.3.5H₂O and [Cr(NH₃)₆](NO₃)₃ displaced the dye from DNA. Similar effects were observed in experiments using the non‐intercalating dye bisbenzimidazole ("Hoechst 33258"). However, singly charged cationic, anionic and uncharged chromium(III) complexes such as: cis‐[Cr(1,10‐phenanthroline)₂Cl₂]Cl.2H₂O, cis‐[Cr(2,2'‐bipyridyl)₂Cl₂]Cl.2H₂O, [Cr(glutathione)₂]Na₂, [Cr(cysteine)₂]Na.2H₂O and [Cr(glycine)₃] were unable to displace both ethidiumbromide and bisbenzimidazole from DNA. There was no evidence for the formation of co‐ordinate bonds between chromium(III) and DNA for any of the above complexes. The charge and type of ligand are important in controlling the interaction of chromium(III) with isolated DNA in vitro. Our findings indicate that the outer sphere interaction of a chromium(III) complex with DNA is weak and unlikely to be the mechanism by which chromate causes DNA impairments in vivo and in vitro.     

Removal of pentachlorophenol from contaminated soil by catalytic oxidation with iron(III)-porphyrin complexes and potassium monopersulfate

Pentachlorophenol (PCP) in contaminated soil was removed by treatment with aqueous solutions of iron(III)-porphyrin complexes as catalysts and potassium monopersulfate (KHSO₅) as the oxygen donor. The contaminated soils were artificially prepared by spiking PCP to the kaolin and ando soils. Three types of iron(III)-porphyrin complexes, tetra(?p-sulfophenyl) porphineiron(III) (Fe(III)-TPPS), tetra(N-methyl-4-pyridil)porphineiron(III) (Fe(III)-TMPyP) and heme, were examined, and Fe(III)-TPPS was found to be the most effective for removing PCP. Although the sequential addition of KHSO₅ was examined, in an attempt to improve the efficiency of PCP removal, it was not effective. In a preliminary test of various aqueous solutions, the addition of humic acid (HA), with a lower degree of humification, led to a significant enhancement in PCP removal. When HA was added to the soil system, the percentages of PCP removal were increased by up to 10% compared to the absence of HA. Therefore, the addition of HA to the catalytic system was useful in enhancing PCP removal from contaminated soil.     

Toxic effect of transition metal complexes on Salmonella typhi,Escherichia coli and Serratia marcescens

The present article describes the synthesis, structural features and toxicological studies of the complexes of the type [M(L)(dipy-amine)(H₂O)] or [M(L)(bendan)(H₂O)] where M?=?Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), H₂L?=?salicylidene-o-aminothiophenol, dipy-amine?=di(2-pyridyal)amine, or bendan?=?bis(benzylidene)1,8-diaminonaphthalene. The complexes have been characterized on the basis of elemental analyses, electronic spectra, magnetic measurement and thermogravimetric analyses. The nature of the bonding has been discussed on the basis of infrared spectral data. A thermal study of the complexes has been carried out to ascertain their thermal stability. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated octahedral structure for these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature. The toxic effects of the investigated complexes were tested against three Gram-negative bacteria, Salmonella typhi, Escherichia coli and Serratia marcescens by the “Disc Diffusion Method”. It is observed that the complexes show higher toxic effects as compared to the ligands, metal salts and control (DMSO), but moderate toxic effects as compared to the standard drug (tetracycline) and the results are discussed.     

In vitro fungitoxic activity of some Schiff bases and their oxovanadium(IV) complexes

The oxovanadium(IV) (VO(IV)) complexes, Schiff bases, vanadyl sulphate, standard fungicides (bavistin and emcarb) and control (dimethyl sulphoxide) were tested for their in vitro fungitoxic activity on A. niger, F. oxysporum and A. flavus. The oxovanadium(IV) complexes show higher fungitoxic activity as compared with the free ligands, vanadyl sulphate and control (dimethyl sulphoxide), but moderate fungitoxic activity as compared with the standard fungicides (bavistin and emcarb). Oxovanadium(IV) complexes have been prepared with biologically active Schiff bases viz. the potassium salt of salicylidene-DL-alanine (sal-ala), 2,2′-bipyridylamine (bipym), bis(benzylidene)ethylenediamine (benen), thiophene-o-carboxaldeneaniline (tca), thiophene-o-carboxaldene-p-toluidine (tct), bis(benzylidene)-1,8-diaminonaphthalene (bendan) or bis(acetophenone)ethylenediamine (acphen). They have been characterized on the basis of elemental analysis, thermogravimetric analysis, magnetic measurements, electronic and infrared spectra. An octahedral geometry has been tentatively assigned to all the complexes.     

Sorption and mobility of polyethylene glycol (PEG 4000) in tropical soils

Millions of tons of polyethylene glycols (PEGs) are manufactured worldwide and most of them will reach conventional sewage disposal systems after industrial utilization. This raises environmental concerns, but not much is known about the environmental fate of these polymers. The main goals of this research were to evaluate sorption and mobility of PEG in sandier soils of Brazil. PEG 4000 was applied to the soils either freely in solution or as a simulated bioassay residue. The bioassay was prepared to simulate PEG as it is present in the animal feces. It allowed us to compare PEG mobility for both forms of environment disposal. PEG showed very low sorption (<22% of the applied PEG) and high mobility potential (>43% of the applied amount in the free-PEG and >24% of the applied amount in the bioassay-PEG experiment) in the studied soils. When PEG was applied, simulating its supply to animal diets, about 30% of its applied amount was retained into the bioassay residues and its leaching potential was reduced, whereas the remaining amount (about 70%) was readily available in solution and could be directly released into the environment.