Iodinated disinfection byproduct formation in a MnO2/I-/EPS system.

Manganese dioxide (MnO2) is a Mn deposit widely accumulated in the corrosion layer of pipelines, and iodide (I-) is a halogen ion frequently detected in waters. The biofilm dwelling on the corrosion scales often secretes extracellular polymeric substances (EPS) into drinking water. The paper aimed to study the I- oxidation by MnO2 and iodinated disinfection byproducts (I-DBPs) formation with biofilm EPS as a precursor. More than 93% of formed free iodine was finally converted into organic iodine in the MnO2/I-/EPS system. Compared with humic acid, EPS had a lower carbonaceous I-DBPs (C-IDBPs) formation while a higher nitrogenous I-DBPs (N-IDBPs) formation. The formation of iodomethanes (I-THMs), iodoacetonitriles (I-HANs) and iodoacetic acids (I-HAAs) decreased with the increase of pH due to the weakening of polarization effect and redox potential, while the iodoacetamides (I-HAcAms) formation achieved the maximum at pH 6.0 due to the difference between the hydrolysis rate of I-HANs and decomposition rate of I-HAcAms. The I-DBPs formation was positively correlated with I- concentration, while negatively correlated with MnO2 dose. Protein components displayed a higher formation of N-IDBPs and C-IDBPs than polysaccharide components due to higher nitrogen proportion and more iodination sites. Among 20 protein monomers, aspartic acid was considered as the most important precursor of the four investigated I-DBPs species. The paper is helpful to understand the I-DBPs formation when I- in the bulk water come into contact with Mn deposits attached by biofilm.

Enhanced formation of carbonaceous and nitrogenous disinfection byproducts from biofilm extracellular polymeric substances undercatalysis of copper corrosion products.

Biofilm formation is ubiquitous on the corroded inner surface of water distribution pipes. Extracellular polymeric substances (EPS) secreted by biofilm microorganisms are nonnegligible precursors of disinfection byproducts (DBPs). The aim was to study the catalysis of copper corrosion products (CCPs, CuO and Cu2+) on the formation of carbonaceous and nitrogenous DBPs (C-DBPs and N-DBPs) with EPS as a precursor. Results indicate that CCPs had a remarkable enhancement on the formation of DBPs, especially N-DBPs. The enhancement by Cu2+ was mainly via homogeneous catalysis initiating from its complexation with EPS, while that by CuO was primarily through heterogeneous catalysis initiating from the polarization of Cl atom in HOCl/OCl-. The enhancement was more evident as pH increased because an alkaline condition favored the electrostatic interactions of CCPs with EPS and HOCl/OCl-. The presence of Br- weakened the enhancement, which may be attributed to that HOBr/OBr- had a much higher reaction rate than HOCl/OCl- towards the low reactive moieties in EPS. Due to more phenolic or unsaturated/conjugated groups, EPS proteins had a higher catalytic formation of DBPs than EPS polysaccharides. Among the major amino acids in EPS proteins for DBPs formation, tyrosine had the highest enhancement on the formation of trihalomethanes, while histidine had the highest catalytic formation of halogenated acetic acids, acetonitriles and acetamides. The study helps to understand the formation of DBPs by the joint actions of EPS and CCPs in drinking water distribution systems.

Facile synthesis and properties of a cation exchange membrane with bifunctional groups prepared by pre-irradiation graft copolymerization.

A new type of a cation exchange membrane named ETFE-g-poly(AA-co-SSS) with bifunctional groups was synthesized by a one-step method. Its preparation by an electron beam-induced pre-irradiation grafting method and the effects of reaction temperature, monomer concentration, pH value of the grafting solution, storage time and temperature of the irradiated poly(ethylene-alt-tetrafluoroethylene) (ETFE) films on the grafting yield were studied. A total concentration of 2 mol L-1 of monomers was found to be beneficial for acrylic acid (AA) and sodium styrene sulfonate (SSS) co-grafting onto the ETFE films. Infrared spectroscopic analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups. The contact angle of the grafted membrane decreased from 94.3 to 46.7° with the increase in grafting yield. The higher the grafting yield, the faster the response and recovery rate with respect to humidity. AFM images showed that the diameter of the grafted chains on the surface of ETFE membranes was about 30 nm. The voltage of the grafted membrane was stable after 100 cycles of charge-discharge; thus, the prepared membranes have great potentials to be used as separators in secondary batteries.

[Biodegradation of methyl tert-butyl ether by stabilized immobilized Methylibium petroleiphilum PM1 cells and its biodegradation kinetics analysis].

Methylibium petroleiphilum PM1, which is capable of degrading methyl tert-butyl ether (MTBE) , was immobilized in calcium alginate gel beads. Several methods were explored to increase the strength of these gel beads. The central composite design analysis indicated that the introduction of 0.2 mol x L(-1) Ca2+ into the crosslinking solution, 1.38 mmol x L(-1) Ca2+ into the growth medium and 0.1% polyethyleneimine (PEI) as the chemical crosslinking agent could increase the stability of the Ca-alginate gel beads with no loss of biodegradation activity. The stabilized immobilized cells could be used 400 h continuously with no breakage and no bioactivity loss. Examination of scanning electron microscope demonstrated that a membrane surrounding the gel beads was formed and the cells could grow and breed well in the stabilized calcium alginate gel beads. Kinetic analysis of the gel bead-degradation indicated that the rate-limiting step was biochemical process instead of intraparticle diffusion process. The diameter of 3 mm affected the biodegradability less while high concentration of PEI induced much more serious mass transfer restraint.