Yangming Lei

Adsorption behavior of phosphate on Lanthanum(III) doped mesoporous silicates material

A series of lanthanum doped meosoporous MCM-41 (LaxM41, x is Si/La molar ratio) was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICP. It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.

Long-term joint effect of nutrients and temperature increase on algal growth in Lake Taihu, China

To study how global warming and eutrophication affect water ecosystems, a multiplicative growth Monod model, modified by incorporating the Arrhenius equation, was applied to Lake Taihu to quantitatively study the relationships between algal biomass and both nutrients and temperature using long-term data. To qualitatively assess which factor was a limitation of the improved model, temperature variables were calculated using annual mean air temperature (AT), water temperature (WT), and their average temperature (ST), while substrate variables were calculated using annual mean total nitrogen (TN), total phosphorus (TP), and their weighted aggregate (R), respectively. The nine fitted curves showed that TN and AT were two important factors influencing algal growth; AT limited growth as algal photosynthesis is mainly carried out near the water surface; N leakage of phytoplankton and internal phosphorus load from sediment explains why TN was the best predictor of peak biomass using the Monod model. The fitted results suggest that annual mean algal biomass increased by 0.145 times when annual mean AT increased by 1.0 degrees C. Results also showed that the more eutrophic the lake, the greater the effect AT had on algal growth. Subsequently, the long-term joint effect of annual temperature increase and eutrophication to water ecosystems can be quantitatively assessed and predicted.

Development of a trickle bed reactor of electro-Fenton process for wastewater treatment

To avoid electrolyte leakage and gas bubbles in the electro-Fenton (E-Fenton) reactors using a gas diffusion cathode, we developed a trickle bed cathode by coating a layer composed of carbon black and polytetrafluoroethylene (C-PTFE) onto graphite chips instead of carbon cloth. The trickle bed cathode was optimized by single-factor and orthogonal experiments, in which carbon black, PTFE, and a surfactant were considered as the determinant of the performance of graphite chips. In the reactor assembled by the trickle bed cathode, H2O2 was generated with a current of 0.3A and a current efficiency of 60%. This performance was attributed to the fine distribution of electrolyte and air, as well as the effective oxygen transfer from the gas phase to the electrolyte-cathode interface. In terms of H2O2 generation and current efficiency, the developed trickle bed reactor had a performance comparable to that of the conventional E-Fenton reactor using a gas diffusion cathode. Further, 123 mg L(-1) of reactive brilliant red X-3B in aqueous solution was decomposed in the optimized trickle bed reactor as E-Fenton reactor. The decolorization ratio reached 97% within 20 min, and the mineralization reached 87% within 3h.

Effects of electrokinetics on bioavailability of soil nutrients

There is growing interest in the potential for applying an electric field to soil to move and stimulate the degradation of contaminants; however, we know little of the impact of this method on the bioavailability of soil nutrients. The effect of electrokinetics (EK [1 V·cm−1]) on the bioavailability of nutritional elements in the soil was examined. Soil organic matter, pH, electrical conductivity, oxidation-reduction potential, available nitrogen, phosphorus, and potassium were monitored before and after remediation. After 60 h of EK remediation, the available N, phosphorus, and potassium in soil were increased by an average of 0.44, 3.31, and 1.25 fold, respectively; whereas the content and speciation of organic carbon in soil changed little. At the same time, the average cadmium (Cd) removal efficiency was approximately 68% for Cd-amended soil (100.63 mg Cd kg−1). Overall, there was an obvious increase in the bioavailability of nutrients after EK remediation. It is concluded from this study that the application of EKs cannot only remove soil pollutants effectively but also enhance the bioavailability of nutrients, thus showing its validity as a viable soil remediation technology.

Enhanced electrokinetic remediation of Cd and Pb spiked soil coupled with cation exchange membrane

Electrokinetic (EK) remediation is one of the popular and promising in situ remediation techniques for metal-contaminated soils, but the remediation effect is strongly affected by soil type and chemical species of contaminants; moreover, pH is very difficult to control. This paper investigates the species of cadmium (Cd) and lead (Pb) in simulating contaminated soil before and after EK remediation, and the soil is a typical silt loam soil from Shanghai. Heavy metal speciation in the soil sample was analysed through a sequential extraction procedure. Cation-exchange membrane (CEM) and conductive solution were applied to improve the remediation efficiency. Both methods help to keep acid conditions and CEM can prevent anions in the cathodic compartment from penetrating into the soil sample system. The pH of the soil specimen was acidic during the test, and Cd was quickly removed from the soil while Pb was removed more slowly. The average removal efficiencies of Cd and Pb were 68.7 and 38.7%, respectively, after 60 h of remediation.

A Trickle Bed Electrochemical Reactor for Generation of Hydrogen Peroxide and Degradation of an Azo Dye in Water

Abstract A trickle bed electrochemical reactor was used to generate hydrogen peroxide in dilute electrolyte and then degrade an azo dye, i.e. reactive brilliant red X-3B in water by electro-Fenton process. The trickle bed reactor was composed of carbon black-polytetrafluoroethylene coated graphite chips. During the preparation of coated graphite chips, coating times and surfactant dosage were optimized to improve electro-generation of H2O2. In addition, the optimal electrolysis conditions for H2O2 electro-generation were obtained as follows, cell voltage of 4.5 V, air flow rate of 0.1 m3/h, electrolyte flow rate of 15 mL/min, and initial pH of 3. Under the given conditions, H2O2 concentration, production rate and current efficiency were 5.01 mmol/L, 134 μmol/(h·cm2) and 63.7%, respectively, after 1 h of electrolysis. With addition of 0.1 mmol/L Fe2+, 123 mg/L X-3B was completely removed from water after 30 min of electro-Fenton treatment, whereas total organic carbon dropped slowly from 17.8 mg/L to 2.28 mg/L (87% mineralization) after 3 h. The trickle bed reactor was sufficient to treat low-strength wastewater or be used in tandem with other treatment units.