Hongxiao Tang

Surface reaction of Bacillus cereus biomass and its biosorption for lead and copper ions

In this study, the surface chemical functional groups of Bacillus cereus biomass were identified by Fourier transform infrared (FTIR) analytical technique. It had been shown that the B. cereus cells mainly contained carboxyl, hydroxyl, phosphate, amino and amide functional groups. The potentiometric titration was conducted to explain the surface acid-base properties of aqueous B. cereus biomass. The computer program FITEQL 4.0 was used to perform the model calculations. The optimization results indicated that three sites-three pKas model, which assumed the cell surface to have three distinct types of surface organic functional groups based on the IR analysis results, simulated the experimental results very well. Moreover, batch adsorption experiments were performed to investigate biosorption behavior of Cu(II) and Pb(II) ions onto the biomass. Obviously, the adsorption equilibrium data for the two ions were reasonably described by typical Langmuir isotherm.

The electrochemical production of highly effective polyaluminum chloride

This paper presents a new electrolytic method for the synthesis of PAC (polyaluminum chloride). The ECR (electrochemical reactor) used aluminum sheets as anode and AlCl3 aqueous solution as electrolyte. This method adopted low voltage and high electric current intensity during electrolysis. Some factors of the electrochemistry and the chemistry of the aqueous solution, affecting the formation of the most effective species of PAC, were also studied. The liquid product of PAC, in which the most effective species, Alb (The polymeric Al component estimated by the ferron method), was above 70% by weight of the total aluminum with a basicity, B (OH/Al molar ratios) = 2.4, was successfully generated. The results measured by the ferron method and Al-27 NMR method showed that the Alb or Al-13 content of the E-PAC (PAC prepared by electrolysis) were obviously higher than that of the general PAC and other coagulants

Synthesis and characterization of poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibre

The poly(acrylaminophosphonic-carboxyl-hydrazide) chelating ion exchange fibre was prepared by the amination and phosphorization reaction of the hydrazine-modified polyacrylonitrile fibre. The structure of the chelating fibre and the same fibre saturated by Cu(II) and Ag(I) ions was investigated by IR spectrometer in detail. In addition, the crystalline and surface characteristics of the chelating fibre were determined by X-ray diffraction and SEM. The higher binding capacities of the fibrous sorbent for Cu(II), Pb(II), Zn(II), Co(II), Ni(II), Hg(II), Cd(II), Mn(II), Cr(III) and Ag(I) and the effect of pH value on adsorption of the chelating fibre for Cu(II) and Hg(II) ions were examined.

Oxidative decolorization of direct light red F3B dye at natural manganese mineral surface

In this paper, the characteristics of natural manganese mineral collected from Guangxi Province. China, including crystalline properties, elemental composition, organic substrates content (0.17%) and BET surface area (29.8 m(2)/g), were determined. By X-ray powder diffraction and fluorescence spectrograph analysis, it is shown that manganese oxide in the natural mineral exists in the crystal structure of alpha-Mn(2)O(3) and the contents of manganese (II) and manganese (IV) oxides are 4.6 and 42.6%, respectively. The solubility experiments show that manganese dissolved in solution can be ignored at a higher pH value, but its significant solubility is observed with the decrease of pH value. Moreover. the decolorization properties of direct light red F3B dye on natural manganese mineral surface were studied by batch technique. The effects of pH value, temperature, inert electrolyte, light, particles concentration and size, the presence of calcium and phosphate as well as oxygen on the decolorization efficiency of the dye were investigated in detail. The results show that the decolorization of the dye is strongly dependent on pH value, with lower decolorization percentage at higher pH values, and the higher concentration of inert electrolyte and temperature favor the decolorization reaction of the dye on the particle surface. By Arrhenius Equation. the apparent activation energy is found to be at 71.7 kJ/mol, indicating the surface chemical reaction as a rate-limiting step in the overall interface process. The illumination enhances the surface chemical reaction of the dye on manganese mineral particles. The decolorization rate of the dye compound is increased with the increase of particle concentration and the decrease of size since the available surface sires grow in number. The presence of phosphate greatly inhibits the decolorization reaction by competitive adsorption on the mineral surface with the dye anion, while the addition of calcium promotes the decolorization rate of direct light red F3B dye

Adsorption of atrazine by natural organic matter and surfactant dispersed carbon nanotubes.

The aggregation and dispersion behaviors of carbon nanotubes (CNTs) can regulate the environmental spread and fate of CNTs, as well as the organic pollutants adsorbed onto them. In this study, multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were surface modified with humic acids from different sources and with surfactants of different ionic types. The dispersion stability of surface modified CNTs was observed by UV-Vis spectrophotometry. The effect of humic acid and surfactant dispersion on the adsorption of atrazine by CNTs was investigated by batch equilibrium experiments. Both humic acid and surfactant could effectively disperse MWNTs, but not SWNTs, into stable suspensions under the studied conditions. Surface modified CNTs had a greatly reduced capacity for adsorption of atrazine. The inhibitory effect of peat humic acid was relatively stronger than that of soil humic acid, but the two surfactants had a similar inhibitory effect on atrazine adsorption by the two CNT types. Increases in surfactant concentration resulted in rapid decreases in the adsorption of atrazine by CNTs when the surfactant concentration was less than 0.5 critical micelle concentration.

The application of preliminary sediment quality criteria to metal contamination in the Le An River

An equilibrium partitioning approach was employed to develop preliminary sediment quality criteria (SQC) for heavy metals in surficial sediments of the Le An River, near the large Dexing copper mine. Acid-volatile sulfide and interstitial water criteria toxic units for single and multiple metals were derived in this study. After comparison, the results indicated that, within different sections of the river, violation of corresponding SQC by current concentrations of copper, lead and zinc occurred to varying extents. This situation is probably attributable to the discharges of acidic drainage carrying a large amount of copper originating from Dexing copper mine, and to wastewaters containing high levels of zinc and lead released from numerous small smelters and panning activities along the banks of the river. The acidity of effluents from mining activities, and the excessive concentrations of multiple metals, particularly copper in the sediments, made dominant contributions to the severe degradation of local benthic ecosystems. These conclusions are in accordance with an assessment made using the integrative sediment quality triad. Based on combined evidence from different approaches, therefore, control at the contaminant sources is urgently required.

Removal of Cu(II), Zn(II), Cd(II) and Hg(II) from waste water by poly(acrylaminophosphonic)-type chelating fiber

The distribution coefficients (D) for Cu(II), Cd(II), Zn(II) and Hg(II) ions and adsorption isotherms of Cd(II) and Hg(II) ions on the poly(acrylaminophosphonic)-type chelating fiber were investigated using the batch reactor system. It was found that D values for the tested metal ions were above the magnitude of 10(3) at pH 5.0, and the order of metal ion affinities was: Hg(II) > Cu(II) > Zn(II) > Cd(ll). At low pH value (2.0), D value for Hg(II) ion was higher than that of the other ions, above 103. The adsorption of Hg(II) and Cd(II) ions on the new chelating fiber followed a Langmuir-type adsorption isotherm. The elution of the metal ions from the chelating fiber column using dilute nitric and hydrochloric acid as eluent were examined. The results show that the elution for Cu(II), Cd(II) and Zn(II) ion was complete using appropriate concentration of hydrochloric acid, while the high concentration of dilute nitric acid was necessary for the quantitative desorption of I-Ig(Il) ion. The breakthrough curves for the metal ions were determined, and the efficient removal of the listed metal ions from model or waste water by the newly developed fibrous sorbent was achieved

Transformations of particles, metal elements and natural organic matter in different water treatment processes

Characterizing natural organic matter (NOM), particles and elements in different water treatment processes can give a useful information to optimize water treatment operations. In this article, transformations of particles, metal elements and NOM in a pilot-scale water treatment plant were investigated by laser light granularity system, particle counter, glass-fiber membrane filtration, inductively coupled plasma-optical emission spectroscopy, ultra filtration and resin absorbents fractionation. The results showed that particles, NOM and trihalomethane formation precursors were removed synergistically by sequential treatment of different processes. Pre-ozonation markedly changed the polarity and molecular weight of NOM, and it could be conducive to the following coagulation process through destabilizing particles and colloids; mid-ozonation enhanced the subsequent granular activated carbon (GAC) filtration process by decreasing molecular weight of organic matters. Coagulation-flotation and GAC were more efficient in removing fixed suspended solids and larger particles; while sand-filtration was more efficient in removing volatile suspended solids and smaller particles. Flotation performed better than sedimentation in terms of particle and NOM removal. The type of coagulant could greatly affect the performance of coagulation-flotation. Pre-hydrolyzed composite coagulant (HPAC) was superior to FeCl3 concerning the removals of hydrophobic dissolved organic carbon and volatile suspended solids. The leakages of flocs from sand-filtration and microorganisms from GAC should be mitigated to ensure the reliability of the whole treatment system.

Particle speciation analysis of inorganic polymer flocculants: an examination by photon correlation spectroscopy

Abstract The particle size distribution for two typical kinds of inorganic polymer flocculants is characterized comparatively by using photon correlation spectroscopy (PCS). The experimental results indicate that there exists large difference in particle speciation distribution between PFCl and PACl prepared under similar conditions. The particle size of PFCl samples range in a narrow distribution. Their mean effective hydrodynamic diameters calculated by translational diffusion coefficient are between 5 and 11 nm. For PACl samples at certain basicity, no visible particle species can be determined. At high basicity, both laboratory prepared and commercial products, show a bimodal distribution: one in 2–5 nm and the other ranges in several decades of nm with wide distribution. The latter may be colloidal aluminum hydroxide and also some aggregates of polymers.

Complexations in illite-fulvic acid-Cu2+ systems

As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous ill ...