Lehua Zhang

Effect of the chemical oxidation demand to sulfide ratio on sulfide oxidation in microbial fuel cells treating sulfide-rich wastewater.

This work focused on studying the effect of the chemical oxidation demand to sulfide ratio (COD/S) on power generation and sulfide oxidation in microbial fuel cells treating sulfide-rich wastewater containing organic contaminants. The maximum power density achieved was 20±1 W m −3 V Anode and the Coulombic yield was 20±2%. The COD/S of influent played an important role in elemental sulfur and sulfate production because of competition between acetate oxidation and element sulfur oxidation to sulfate in the anode. When the COD/S was 12.50/1, more than 74.0% of sulfide was converted into elemental sulfur after 24 hours of operation. The effect of the COD/S on power generation was negligible when the COD/S ranged between 4.85/1 and 18.53/1. After 24 hours, the COD removals were 110±6, 213±9, 375±8 and 410±10 mg l −1 when the COD/S was 4.85/1, 8.9/1, 12.5/1 and 18.53/1, respectively. The COD removal increased with the increasing COD of the influent, which fitted to the model of first-order reaction kinetics.

Decrease of dissolved sulfide in sewage by powdered natural magnetite and hematite.

Natural magnetite and hematite were explored to decrease sulfide in sewage, compared with iron salts (FeCl3 and FeSO4). A particle size of magnetite and hematite ranging from 45 to 60μm was used. The results showed that 40mgL-1 of powdered magnetite and hematite addition decreased the sulfide in sewage by 79%and 70%, respectively. The achieved decrease of sulfide production capacities were 197.3, 210.6, 317.6 and 283.3mgSg-1Fe for magnetite, hematite, FeCl3 and FeSO4 at the optimal dosage of 40mgL-1, respectively. Magnetite and hematite provided a higher decrease of sulfide production since more iron ions are capable of being released from the solid phase, not because of adsorption capacity of per gram iron. Besides, the impact on pH and oxidation-reduction potential (ORP) of hematite addition was negligible; while magnetite addition resulted in slight increase of 0.3-0.5 on pH and 10-40mV on ORP. Powdered magnetite and hematite thus appear to be suitable for sulfide decrease in sewage, for their sparing solubility, sustained-release, long reactive time in sewage as well as cost-effectiveness, compared with iron salts. Further investigation over long time periods under practical conditions are needed to evaluate the possible settlement in sewers and unwanted (toxic) metal elements presenting as impurities. CAPSULE ABSTRACT Powdered magnetite and hematite were more cost-effective at only 30% costs of iron salts, such as FeCl3 and FeSO4 for decreasing sulfide production in sewage.

Increasing power generation of microbial fuel cells with a nano-CeO2 modified anode

ABSTRACT Nano-CeO2 was used to modify the carbon felt anode in microbial fuel cell (MFC). The MFC with the modified anode obtained the higher closed circuit voltage resulting from the lower anode potential, the higher maximum power density (2.94 W m−2), and the lower internal resistance (77.1 Ω). Cyclic voltammetry (CV) results implied that the bioelectrochemical activity of exoelectrogens was promoted by nano-CeO2. Electrochemical impedance spectroscopy (EIS) results revealed that the anodic charge transfer resistance of the MFC decreased with modified anode. This study demonstrates that the nano-CeO2 can be an effective anodic catalyst for enhancing the power generation of MFC.

Abatement of sulfide generation in sewage by glutaraldehyde supplementation and the impact on the activated sludge accordingly

Hydrogen sulfide emission in sewer systems is associated with toxicity, corrosion, odour nuisance and high costs treatment. In this study, a novel method to inhibit sulfide generation from sewage by means of glutaraldehyde supplementation has been suggested and evaluated under anaerobic conditions. Different concentrations of glutaraldehyde at 10, 15, 20, 30 and 40 mg·L−1 have been investigated. Besides, the possible impacts of glutaraldehyde supplementation on an activated sludge system and an appraisal of the economic aspects are presented as well. As observed from the experimental results, a dosage of 20 mg·L−1 glutaraldehyde resulted in a significant decrease of the sulfide production by 70%–80% in the simulated sewage. Moreover, the impacts of additional glutaraldehyde at 20 mg·L−1 on activated sludge, in terms of chemical oxygen demand removal and oxygen uptake rates, were negligible. From an economical point of view, the cost of the commercial glutaraldehyde products required in the operation, which was calculated on the basis of activated sulfide removal avoidance, was around €3.7–4.6 S·kg−1. Therefore it is suggested that glutaraldehyde supplementation is a feasible technique to abate the sulfide problems in sewer systems. Yet further research is required to elucidate the optimum “booster” dosage and the dosing frequency in situ accordingly.

The Simulation of an Industrial Fixed Bed Reactor for Methanol Dehydration to Dimethyl Ether

Compared to methane and methanol, dimethyl ether seems to be a superior candidate for high quality diesel fuel in the near future. To meet the continuously increasing global requirements, a larger scale reactor is needed to produce more dimethyl ether. A heterogeneous one-dimensional model was developed to simulate a staged adiabatic fixed bed reactor for the catalytic dehydration of methanol to dimethyl ether. To verify the proposed model, the simulated catalyst bed temperature has been compared to available data from an industrial reactor. A good agreement has been found between the simulation and plant data. Also, the effects of some operational parameters, such as feed flow rates, the inlet temperatures of methanol, pressure, and catalyst particle diameter on reactor behavior were investigated. The simulated results show that this model is reasonable and reliable.

A Study on the Processing for Lube Base Oil from Xijiang and Neil Blended Crude Oil No. 3 Fraction

Abstract Ketone-benzol dewaxing, furfural refining, clay finishing and furfural refining, ketone-benzol dewaxing, clay finishing were selected, respectively, to process lube feedstock. The base oils processed by furfural refining, ketone-benzol dewaxing, clay finishing or ketone-benzol dewaxing, furfural refining, clay finishing were determined regarding their different chemical nature and their different physical properties. Group analysis, elemental analysis, infra-red spectrum, and 1H nuclear magnetic resonance were also used to investigate the structure characteristics, the hydrocarbon characteristic, and branch sites of hydrocarbon of the base oils. Experimental data shows that furfural refining, ketone-benzol dewaxing, clay finishing may be available for factories in the manufacturing process of lube feedstock from Xijiang and Neil (1:1) crude oil No. 3 fraction, but better properties of base oil can be obtained using more rigorous process conditions.