Analysis on the effect of operating conditions on electrochemical conversion of carbon dioxide to formic acid

Electrochemical reduction of CO₂ to HCOOH was performed on a Sn electrode using a proton exchange membrane-embedded electrolysis cell. The effects of reaction conditions such as catholyte and anolyte types, reduction potential, catholyte pH, and reaction temperature on the amount of HCOOH and its faradaic efficiency were investigated. Four different electrolytes (KOH, KHCO₃, KCl, KHSO₄) were chosen as the candidate catholyte and anolyte; the most suitable electrolyte was chosen by monitoring the amount of HCOOH and faradaic efficiency. The effect of the pH of the selected catholyte on the conversion of CO₂ to HCOOH was also investigated. In addition, the reaction temperature was varied and its effect was studied. From the observations made, we determined the optimal reaction conditions for the production of HCOOH via the electrochemical reduction of CO₂ by a systematic approach.     

Biological treatment of wastewater produced during recycling of spent lithium primary battery

Wastewater produced during recycling of spent lithium primary battery was biologically treated with Acidithiobacillus ferrooxidans to decrease the pH and metal concentration. Since the wastewater contains high concentrations of Cr, Ni, and Li, the effects of these metals on the bacterial activity in a 9 K medium were also investigated. Samples of the medium with different metal concentrations were treated, and the oxidation ratio of Fe²⁺ ions was measured to examine the activity of bacteria. In the treatment of simulated wastewater, the presence of Cr and Ni ions with concentrations of 8000 g m^?3 and 13,000 g m^?3, respectively, did not inhibit the bacterial activity, whereas the oxidation ratio of Fe²⁺ ions was observed to be low in the medium when Li ion was present with a concentration at 5000 g m^?3. This observation suggested that at this concentration, Li ion suppressed the bacterial activity. In the case of treatment of real wastewater containing Cr, Ni, and Li, the oxidation ratio of Fe²⁺ to Fe³⁺ was observed to be low while the Fe concentration and pH decreased to 21,633 g m^?3 and 1.8, respectively. Thus, the wastewater produced during the recycling of spent lithium primary batteries can be effectively treated biologically for re-circulating in the recycling process.     

Study of impact energy propagation phenomenon and modal characteristics of an armored vehicle undergoing high velocity impact

A new manufacturing technology is being employed to build a new type of armored vehicle. While thick panels are welded together in the old manufacturing technology, relatively thin panels are welded to a frame structure in the new manufacturing technology. The structural integrity of the new type of armor vehicles can be maintained mainly by the frame structures while the panel thickness is reduced significantly to reduce the total vehicle weight. Since the dynamic characteristics of a frame-panel hybrid structure are different from those of the old type of structure which consists of only thick panels, they should be identified to achieve a good performance of the vehicle. For this purpose, a proper FE model of the hybrid type of structure needs to be developed. In the present study, FE models are proposed to represent the frame-panel hybrid type structure efficiently. The impact energy propagation, the transient response and the modal characteristics are investigated with the FE models. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong-Hee Yoo received a B.S. and M.S. degree in Mechanical Engineering from Seoul National University in 1980 and 1982. He then went on to receive his Ph.D. degree from Michigan State University in 1989. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Hanyang University in Seoul, Korea. His research interests are in the area of Flexible body dynamics, vibration.     

Influence of process conditions on product yield of waste tyre pyrolysis- A review

Waste tyres have become a grave concern as their accumulation is aggregating every year. Not only the size of waste tyre has to be reduced, but also some useful energy has to be recovered out of it as the world badly requires energy from alternate sources. Pyrolysis is one such method to extract energy potential products from waste tyres. It is extensively used to generate carbon black (solid product), tyre-oil (liquid product) and syngas (gas product) from waste tyres. In that connection, this article discusses the effect of various parameters on the product composition of pyrolysis of waste tyres. The current usage of pyrolysis products and their typical characteristics are also discussed in this critique. Of late, extraction of high value added products, such as activated carbon from carbon black, and limonene from tyre-oil is gaining attention. The article also throws some light on the application and generation routes of activated carbon and limonene from waste tyres.     

Electrochemical synthesis of ammonia from water and nitrogen catalyzed by nano-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> suspended in a molten LiCl-KCl-CsCl electrolyte

Nano-Fe₂O₃ and CoFe₂O₄ were suspended in molten salt of alkali-metal chloride (LiCl-KCl-CsCl) and their catalytic activity in electrochemical ammonia synthesis was evaluated from potentiostatic electrolysis at 600 K. The presence of nanoparticle suspension in the molten chloride resulted in improved production of NH₃, recording NH₃ synthesis rate of 1.78×10^?10 mol s^?1 cm^?2 and 3.00×10^?10 mol s^?1 cm^?2 with CoFe₂O₄ and Fe₂O₃, which are 102% and 240% higher than that without the use of a nanocatalyst, respectively. We speculated that the nanoparticles triggered both the electrochemical reduction of nitrogen and also chemical reaction between nitrogen and hydrogen that was produced from water electro-reduction on cathode. The use of nanocatalysts in the form of suspension offers an effective way to overcome the sluggish nature of nitrogen reduction in the molten chloride electrolyte.     

Modeling and analysis of circulation variables of continuous sorbent loop cycling for CO<Subscript>2</Subscript> capture

Carbon capture and storage (CCS) technologies are a cornerstone for reducing CO₂ emissions from energy and energy-intensive industries. Among the various CCS technologies, solid sorbent looping systems are considered to be potentially promising solutions for reducing CO₂ capture energy penalty. We present an evaluation module for a carbonator with sorbent looping cycle to calculate the carbonation efficiency. The module incorporates a simple sorbent activity model, and the solid/gas balances are constructed by assuming simple reactor mixing quality. By conducting simulations, we examine the variation in the carbonation efficiencies as a function of the sorbent looping operation factors and discuss an optimum operating strategy.     

Highly sensitive and selective dopamine detection by an amperometric biosensor based on tyrosinase/MWNT/GCE

Dopamine (3,4-dihydroxylphenyl ethylamine) is the most significant neurotransmitter in the human nervous system. Abnormal dopamine levels cause fatal neurological disorders, and thus measuring dopamine level in actual samples is important. Although electrochemical methods have been developed for detecting dopamine with high accuracy, certain substances (e.g., ascorbic acid) in actual samples often interfere with electrochemical dopamine detection. We developed tyrosinase-based dopamine biosensor with high sensitivity and selectivity. An electrochemically pretreated tyrosinase/multi-walled carbon nanotube-modified glassy carbon electrode (tyrosinase/MWNT/GCE) was prepared as an amperometric biosensor for selective dopamine detection. For optimizing the biosensor performance, pH, temperature, and scan rate were investigated. The electrochemically pretreated tyrosinase/MWNT/GCE exhibited not only the highest sensitivity (1,323 mAM^?1 cm^?2) compared to previously reported tyrosinase-based dopamine sensors, but also good long-term stability, retaining 90% of initial activity after 30 days. Additionally, ascorbic acid, a major interfering substances, was not oxidized at the potential used to detect dopamine oxidation, and the interfering effect of 4mM ascorbic acid was negligible when monitoring 1mM dopamine. Consequently, the electrochemically pretreated tyrosinase/MWNT/GCE is applicable for highly selective and sensitive dopamine detection in actual samples including interfering substances, thereby extending the practical use to monitor and diagnose neurological disorders.     

Evaluation of multiloop chemical dosage control strategies for total phosphorus removal of enhanced biological nutrient removal process

We developed several control algorithms and compare their control performances for controlling the total phosphorous (TP) concentration in wastewater treatment plant, which has strong influent disturbances and the disturbance effects should be removed while maintaining better effluent quality. An anaerobic - anoxic - oxic (AAO) process, which is a well-known advanced nutrient removal process, was selected as a case study, which is modeled with activated sludge model no. 2. Six control strategies for TP control with a polymer addition were implemented in AAO process and evaluated by the plant’s performance, where the costs of the dosed chemical were compared among the six controllers. The experimental work showed that the advanced control techniques with feedback, feedforward and feedratio controllers were able to control the TP concentration in the effluent, which must be less than 1.50 g P/m³ which is the legal limitation, while reducing the necessary chemical cost. The results showed that the best TP removal performance in the effluent TP removal could be achieved by advanced feedback controller with the tuned control parameters, which showed the best effluent quality and control performance index as well as the cheapest cost of chemical dosage among the six TP control strategies.