Zucheng Wu

Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell.

Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm−2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm−2 with an open circuit voltage of 0.38 V at 60°C.

A novel fluidized electrochemical reactor for organic pollutant abatement

To promote organic pollutant treatment efficiency by improving mass transfer, a novel fluidized electrochemical reactor that integrated advanced electrochemical oxidation process (AEOP) with activated carbon (AC) fluidization in a single cell was developed for model pollutant p-nitrophenol (PNP) abatement. Synergetic effect on COD removal was found in such a combined process and the COD removal efficiency was enhanced to be 97.8%. The combined process has been proved to be a promising abatement process for biorefractory organic pollutants degradation, which is advantageous over using either AEOP or adsorption alone. The roles of the location of AC in the cell, liquid flowrate, AC mass and initial PNP concentrations on COD removal were investigated to optimize the performance. A lumped kinetic model based on adsorption/electrocatalysis/oxidation mechanism for COD removal was proposed to predict the role of adsorption, electrocatalysis and oxidation in the combined process. The output of the kinetic model was found to be in good agreement with the experimental data obtained at various initial PNP concentrations and AC mass.

Culture of Spirulina platensis in human urine for biomass production and O2 evolution

Attempts were made to culture Spirulina platensis in human urine directly to achieve biomass production and O2 evolution, for potential application to nutrient regeneration and air revitalization in life support system. The culture results showed that Spirulina platensis grows successfully in diluted human urine, and yields maximal biomass at urine dilution ratios of 140∼240. Accumulation of lipid and decreasing of protein occurred due to N deficiency. O2 release rate of Spirulina platensis in diluted human urine was higher than that in Zarrouk medium.

ELECTROCATALYTIC DEGRADATION OF PHENOL IN ACIDIC AND SALINE WASTEWATER

ABSTRACT The electrocatalytic degradation of low concentration of phenol (100–800 mg L−1) as a model contaminant for wastewater treatment was studied on modified β-PbO2 anode. Various affected factors such as current density (7.5–30 mA cm−2), reaction temperature (5–60°C), pH (2–6), salinity of the electrolyte (0.5–10 g L−1 K2SO4), and circulation rate (100–2400 mL min−1) were investigated. Phenol at a concentration level of 100 mg L−1 could be completely degraded within 30 min under the current density of 7.5 mA cm−2 with the addition of K2SO4 (1.0 g L−1) at pH 5.6 and temperature 60°C. The method showed promising application for treating phenolic wastewater of high salinity and acidity. Analysis of the intermediates of the phenol degradation products indicated good catalytic characteristics of the anode for breaking down the aromatic compounds to organic acids. The overall degradation of phenol was considered a controlled process of mass-transfer. According to the proposed model and Arrheniuss Law, the activation energy was calculated 23.8 kJ mol−1.

Removal of Phenolic Compounds by Electro-assisted Advanced Process for Wastewater Purification

Electro-assisted advanced process was developed for wastewater treatment of phenolic compounds. A series of correlative experiments were carried out: the degradation of phenol by the advanced electrochemical oxidation process, the degradation of chlorophenol by the photo-electrocatalysis, and the degradation of chlorophenol by pair electrodes. It was found that phenol and chlorophenol could be removed rapidly and effectively at initial concentration of 100–400 mg L−1, current density of 3.2–27.5 mA cm−2, and applied voltage of 2–5 V. The combination of electrocatalytic and UV radiation greatly accelerated the removal efficiency. The dechlorination of chlorophenol could be achieved under cathodic reduction so that it could be further oxidized more quickly and completely. The mechanism of dechlorination was proposed to be the indirect dechlorination by atomic hydrogen. The electro-assisted advanced processes were suitable for the treatment of the phenolic compounds.

Synergetic effects of anodic–cathodic electrocatalysis for phenol degradation in the presence of iron(II)

A novel electrocatalysis method for phenol degradation was described using a beta-PbO2 anode modified with fluorine resin and a Ni-Cr-Ti alloy cathode. In case of air sparging at the cathodic zone, the techniques of anodic-cathodic electrocatalysis (ACEC) and ferrous ion catalyzed anodic-cathodic electrocatalysis (FACEC) in the presence of iron(II) were developed. Both of ACEC and FACEC were more effective than anodic electrocatalysis (AEC). The percentage of phenol eliminated by FACEC could increase by nearly 30% compared with that of AEC, and the current efficiency could reach to 70%. Important operating factors such as ferrous ion concentration, air-sparging rate and applied current were investigated and it was found that such beneficial effects could be achieved at a suitable current and ratio of the concentration of ferrous ion to the air sparged. The mechanism of phenol degradation is proposed to be the generation of hydroxyl radicals concerned with the two electrodes. Results also indicated that the process provided an efficient way to regenerate ferrous ion compared with the conventional Fentons system.

Waste Stabilization Ponds and Lagoons

One of the simplest forms of biological treatment processes is the stabilization pond or stabilization lagoon. It is also the most common industrial wastewater treatment facility. This versatile installation serves many basic purposes, including: (a) storage or impoundment of wastewater; (b) settling and removal of suspended solids; (c) storage or impoundment of settled solids; (d) equalization; (e) aeration; (f) biological treatment; and (g) evaporation. The relative simplicity and low operating costs of a stabilization pond make it the preferred technology for handling, treatment and disposal of industrial wastewater as well as municipal wastewater for small communities. Besides the description of ponds complex ecological system and the complicated reactions that take place, the chapter covers the system variables, design criteria, process control, capital and operating costs, applications and examples of process design.

Nitrification of human urine for its stabilization and nutrient recycling

Nitrification of human urine performed for its stabilization, and culture of Spirulina platensis in the nitrified human urine were investigated for nutrient recovery. With daily adjusting to pH 8 and keeping high dissolved oxygen concentration, mean 95.0% of NH(4)-N in human urine can be finally stabilized and oxidized to NO(3)-N. Furthermore, this nitrified human urine seems to be an ideal culture medium for S. platensis. Without pH adjustment, only about 50.0% NH(4)-N could be converted, i.e. NH(4)NO(3) would be formed. Under low dissolved oxygen concentration, mainly short nitrification (from NH(4)-N to NO(2)-N) occurred.

Microbial Fuel Cells for Bioenergy and Bioproducts

Redox reactions are essential in microbial bioenergetics. Oxidation of an organic carbon and reduction of an oxidant such as oxygen, sulfate and nitrate in the cytoplasm of a microbe. This respiration process provides energy for various cellular activities and maintenance as well as building blocks for organic syntheses. Because the cellular respiration efficiency is around 40, 60% of the energy is released in the form of unrecoverable low-grade heat. No electricity is produced from the redox reaction because the electrons released by the oxidation reaction are taken up locally by the reduction reaction in the cytoplasm. The purpose of a microbial fuel cell (MFC) is to harvest the electrons from organic carbon oxidation by employing electrogenic microbes to donate the electrons to an anode in the absence of an utilizable oxidant around the anode. The electrons flow through an external circuit to drive a load before returning to a cathode where they are used for reduction of an oxidant. MFCs can digest low-grade organic carbon sources while yielding high Coulombic efficiencies. They present a potentially attractive alternative for the sustainable production of bioenergy and bioproducts from renewable organic feed streams through biocatalysis by microorganisms. In recent years, heightened concerns over depleting fossil fuel supplies, most noticeably petroleum, and global warming due to increased carbon emission, many efforts have been devoted to MFC research to debottleneck various factors that hamper practical applications of MFCs. Although no large-scale applications have been reported, the improvements in MFC designs and operations have made MFCs closer to eventual practical applications in the production of bioenergy and bioproducts from feed streams that are typically wastes such as wastewater. This chapter reviews various advances in the understanding of MFC mechanisms, reactor designs and operations for improved production of renewable bioenergy and bioproducts such as hydrogen, methane, hydrogen peroxide and ethanol. The limitations, areas for improvement and perspectives for future outlooks of MFCs are also discussed.

Remediation of chromium-slag leakage with electricity cogeneration via a urea-Cr(VI) cell

Chromium pollution has been historically widespread throughout the world. Most available remediation technologies often require energy consumption. This study is aimed to develop electrochemical remediation for Cr(VI) in chromium-slag leakage with self-generated electricity. Dynamic leaching experiments of chromium-slag samples were conducted to survey the release and leaching behavior of Cr(VI). Based on previous work, a unique urea-Cr(VI) was designed, in which urea was employed as the fuel and Cr(VI) from the leakage of the dichromate slag served as the oxidant. Furthermore, the electrochemical results showed that the removal percent of Cr(VI) was more than 96% after 18 h with the leakage Cr(VI) concentration of 2.69 mM. The open circuit potential (OCP) varied in the range of 1.56 ~ 1.59 V under different initial Cr(VI) leakage concentrations. The approach explores the feasibility of the promising technique without the need of energy input for simultaneous chromium-slag remediation and generation of electricity.