Synthesis of visible light-responsive cuprous oxide/sunflower stem pith hybrid materials for detoxification of methylene blue.

The detoxification of dye-contaminated water by photocatalysis has become a research priority. Here, a novel hybrid material, cuprous oxide/sunflower stem pith (Cu2O/SSP), was successfully synthesized in situ, using copper hydroxide gel, prepared by ion exchange, as the precursor to Cu2O. The presence of Cu2O nanoparticles on the SSP was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction analyses. Using methylene blue (MB) as the target pollutant, Cu2O/SSP delivered excellent adsorption-photocatalytic degradation and was readily photoregenerated. Cu2O/SSP removed 72.7% of MB after 60 min under visible light irradiation, an increase of 15.6 % compared with unmodified SSP. SSP plays three roles in the removal of MB: it acts as an adsorbent for the MB, a carrier for the Cu2O nanoparticles and it also inhibits photocorrosion of Cu2O. The mechanism of adsorption-photocatalysis by Cu2O/SSP was investigated and a description of the mechanism is provided. This study paves the way for the detoxification of dye-containing wastewater using hybrid biomass materials.

Assessment of transportation processes of polyacrylamide in chernozem and saline soil by numerical model.

Polyacrylamide (PAM) was studied in two characteristic soils in Daqing City: chernozem and saline soil. 120 mg L-1 of KBr was used as a conservation tracer to estimate diffusion coefficients and pore velocities of chernozem and saline soil by using the breakthrough curves (BTCs) of Br-. Isothermal adsorption equations were coupled with the traditional two-site model to establish the transportation equation of PAM. The results of comparing the simulation curve with the BTCs of PAM at different rates showed that the transportation equation of PAM could simulate the transport process of PAM in soil column accurately. PAM behaved as non-equilibrium adsorption in both soils by calculating the kinetic parameters in this equation. The results of this work not only confirmed the kinetic parameters of PAM in both soils, but also found that there is a good liner relationship between the mass transfer coefficient and pore velocity. The R2 values of the two linear equations are 0.983 and 0.979. These linear equations provide a good prediction basis for site prediction. In addition, it was found that organic matter is the main influence factor for the adsorption capacity of chernozem causing significantly larger than that of saline soil.

Ultrahigh-flux (>190,000 L·m-2h-1) separation of oil and water by a robust and durable Cu(OH)2 nanoneedles mesh with inverse wettability.

Single-stage oil/water separation membranes usually suffer from weak chemical stability, susceptible mechanical damage and relatively low permeating flux, and the sophisticated preparation processes also limit their massive utilization. In this work, Cu(OH)2 nanoneedles coated copper mesh (CM) is prepared by simple and eco-friendly anodic oxidation at a current density of 4 mA/cm2 for 6 min, which is the most efficient route reported so far. The mesh exhibits outstanding superhydrophilicity and underwater superoleophobicity towards various oils with contact angles up to 164.9°, achieving superior oil/water separation efficiency of above 99.5% and ultrahigh permeating flux of 191 160 L·m-2h-1 solely driven by gravity. Impressively, the Cu(OH)2/CM demonstrates excellent chemical stability and anti-fouling performance when exposed to acidic and strongly alkaline solutions, saturated NaCl solution and various organic solvents. High durability to withstand mechanical challenges, e.g. high-power sonication and sand abrasion, is experimentally confirmed owing to strong cohesional strength of Cu(OH)2 nanoneedles on CM surface. Importantly, the Cu(OH)2/CM exhibits favorable long-term recyclability with stable microstructure morphologies even after 50 cycles. These distinct advantages endow the Cu(OH)2/CM to be an ideal candidate to efficiently separate oil pollutants from water. The oil/water separation mechanisms are proposed based on the concept of intrusion pressure.

Adsorption behaviors of methylene blue on sunflower stem pith.

Adsorption behaviors of methylene blue (MB) from aqueous solution using sunflower stem pith (SSP) as adsorbent were investigated. The effects of adsorption conditions such as adsorption time, initial concentration of MB and dosage of SSP on the detoxification of MB were examined. The equilibrium adsorption data were analyzed using three well-known isotherms: Langmuir, Freundlich and Temkin. The results indicated that the Langmuir isotherm fitted well to the data as compared with another isotherm model. The maximum adsorption capacity calculated by the Langmuir isotherm model was 277 mg/g at 338 K. Kinetic analyses were conducted using pseudo first order, pseudo second order and the Elovich model. The regression results showed that the MB adsorption was described by the pseudo second order model. Different thermodynamic parameters such as Gibb's free energy (ΔGo), standard enthalpy change (ΔHo) and standard entropy change (ΔSo) were also evaluated. The results showed that the detoxification of MB using SSP as adsorbent was feasible, non-spontaneous and exothermic under experimental conditions.

Oxidation of oily sludge in supercritical water.

The oxidation of oily sludge in supercritical water is performed in a batch reactor at reaction temperatures between 663 and 723 K, the reaction times between 1 and 10 min and pressure between 23 and 27 MPa. Effect of reaction parameters such as reaction time, temperature, pressure, O(2) excess and initial COD on oxidation of oily sludge is investigated. The results indicate that chemical oxygen demand (COD) removal rate of 92% can be reached in 10 min. COD removal rate increases as the reaction time, temperature and initial COD increase. Pressure and O(2) excess have no remarkable affect on reaction. By taking into account the dependence of reaction rate on COD concentration, a global power-law rate expression was regressed from experimental data. The resulting pre-exponential factor was 8.99 x 10(14)(mol L(-1))(-0.405)s(-1); the activation energy was 213.13+/-1.33 kJ/mol; and the reaction order for oily sludge (based on COD) is 1.405. It was concluded that supercritical water oxidation (SCWO) is a rapidly emerging oily sludge processing technology.

Effect of components in activated sludge liquor on membrane fouling in a submerged membrane bioreactor.

By a membrane bioreactor with a settle tank in long-term operation and batch experiments, the effects of flocs, soluble microorganism products (SMPs) and metal ions in activated sludge liquor on membrane fouling were investigated. The results showed that foulants absorbed each other and formed a fouling layer as a "second membrane" influencing the permeability of the membrane. The "gel layer" caused by SMPs and "cake layer" by flocs showed great differences in morphology by analysis of scanning electron microscope and atomic force microscope. The "gel layer" was more compact and of poor permeability. When the membrane flux was 40 L/(m(2) x h), the rate of membrane fouling caused by supernatant (0.011 MPa/h) was greater than that by sludge liquor (0.0063 MPa/h). SMPs played very important roles on membrane fouling. In the bulking sludge, with SMPs increasing, the rate of membrane fouling (0.0132 MPa/h) was faster. While after flocculation of the SMPs, the rate of fouling decreased to 0.0034 MPa/h. Flocs could keep holes in their overlaps. They could alleviate membrane fouling by preventing the SMPs directly attaching on membrane surface.

Analysis of phosphate-accumulating organisms cultivated under different carbon sources with polymerase chain reaction-denaturing gradient gel electrophoresis assay.

To investigate the microbial communities of microorganisms cultivated under different carbon sources, three sequencing batch reactors were operated. They were supplied with sewage, glucose and sodium acetate as carbon sources respectively and showed high phosphorus removal performance. The results of denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified (PCR) 16S rDNA fragments demonstrated that beta-protebacteria, Actinomyces sp. and gamma-protebacteria only exited in 1 # reactor. The microbiological diversity of 1 # reactor exceeded the other two reactors. Flavobacterium, Bacillales, Actinomyces, Actinobacteridae and uncultured bacteria (AF527584, AF502204, AY592749, AB076862, AJ619051, AF495454 and AY133070) could be detected in the biological phosphorus removal reactors.