Enhancement of acidic dye biosorption capacity on poly(ethylenimine) grafted anaerobic granular sludge.

Developing a novel biosorbent with high capacity is crucial to remove dyes from waters in an efficient way. This study demonstrated that porous anaerobic granular sludge could be grafted with polyethylenimine (PEI), which definitely improved the sorption capacity towards Acid Red 18 (AR18) removal. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) study revealed that the PEI modification introduced a large number of amino groups on the surface of sludge, and the amino groups played an important role in the adsorption of dye molecule. Analysis of sorption data using a Boyd plot confirms the film diffusion was the rate-limiting step. The equilibrium data were well fitted Langmuir model, with a maximum AR18 uptake of 520.52 mg/g. Removal of AR18 decreased with the increasing pH and the maximum color removal was observed at pH 2.0. The sorption energy calculated from Dubinin-Radushkevich isotherm was found to be less than 8 for the biosorption of AR 18, which suggested that the biosorption processes of dye molecule onto modified anaerobic granules could be taken place by physical adsorption. Various thermodynamic parameters, such as ΔG(0), ΔH(0) and ΔS(0), were also calculated, which indicated that the present system was spontaneous and endothermic process.

Aerobic granulation for nitrogen removal via nitrite in a sequencing batch reactor and the emission of nitrous oxide.

In this study, the granulation of nitrifying-denitrifying via nitrite process in a sequencing batch reactor (SBR) as well as N(2)O emission patterns was investigated. After 60 days of operation, 0.8 mm granules were obtained, and partial nitrification was achieved after NH(4)(+)-N was raised to 350 mg/L. Fluorescence In-Situ Hybridization (FISH) analysis indicated that a fairly large proportion of ammonia-oxidizing bacteria (AOB) was close to the surface but nitrite-oxidizing bacteria (NOB) were rarely found. Batch experiments showed that 64.0% of NH(4)(+)-N in influent was transformed into NO(2)(-)-N, which showed the granules had excellent partial nitrification ability. Inhibition of free ammonia (FA) and limited DO diffusion within granules may contribute to the development and stabilization of partial nitrification. This process did not simultaneously lead to increased N(2)O production. N(2)O emissions at the anoxic and aerobic phases were 0.06 and 13.13 mg N(2)O/cycle, respectively.

[Study on phosphorus(P) fixation in the sediment of lake using the clays modified by LaCl3].

14 kinds of clay modified by LaCl3 were prepared and their phosphorus(P) fixation was studied. The effect of pH on adsorption rate of P using kaolin modified by LaCl3 and dissolved concentration of La3+ from them were also discussed. The results showed that the fixation rates of P using clay modified by LaCl3 were improved to 52% - 95% from 3% - 14% using unmodified clay. The maximum adsorption rate of P using kaolin modified by LaCl3 was 94.85% on the pH value of 5. Under the condition of pH range from 4 to 8, the P adsorption rate was higher than 80%. When the pH value was higher than 6.5, the dissolved concentration of La3+ from the modified clay was lower than 0.017 8 mg/L.

[Atomic force microscope analysis of adsorption and flocculation behaviors of polydiallyldimethylammonium salts: influence of counterion].

High molecular weight polydiallyldimethylammonium nitrate (PDADMANO3) and polydiallyldimethylammonium sulfate (PDADMASO4) were prepared from polydiallyldimethylammonium chloride (PDADMAC). The effects of univalent counterions (Cl-, ON3-) and bivalent counterion (SO4(2-) on solution, absorption and flocculation properties of polydiallyldimethylammonium salts (PDADMAX) were investigated by conductivity, reduced viscosity, atomic force microscopy (AFM), residual turbidity, distributions of zeta potential and flocculation index of kaolin suspension. The results show that different counterions possess significant effects on solution properties, absorption and flocculation behaviors of PDADMAX. PDADMANO3 shows stronger flocculation efficiency and "neutralization action", whereas PDADMASO4 shows the wider optimum dosage and larger floc size, as well as "bridging action". In particular, AFM image of single polyelectrolyte polymer is a valuable tool for the analysis of the absorption and flocculation mechanism of polyelectrolye.

A cleaner two-step synthesis of high purity diallyldimethylammonium chloride monomers for flocculant preparation.

In order to improve the flocculation efficiency of polydiallyldimethylammonium chloride (PDADMAC), high molecular weight PDADMAC should be prepared from high purity diallyldimethylammonium chloride(DADMAC) monomers. In this paper, a cleaner method with microwave irradiation and alkali solidification was proposed for preparing high pure DADMAC by selective heating under low temperature, and the prepared high purity DADMAC is characterized using FTIR and atomic absorption spectrometry. The new method provides a solution to the key technical problem of PDADMAC synthesis. Comparing with the conventional methods, the results showed that the advantages of the novel synthesis include: (a) high purity DADMAC is improved from 57% to 71%; (b) reaction time of tertiary amine preparation is shortened from 6 h to 7 min; (c) water instead of acetone was used as reaction medium; (d) toxic by-products, wastewater and waste gas are eliminated. Flocculant made from the synthesized high purity DADMAC monomers was proved more efficient in flocculation tests.