Lactic acid, the most widely occurring hydroxycarboxylic acid, is an enigmatic chemical. It was discovered a long time ago and its use in food preservation and processing and as a specialty chemical has grown over the years with current production of about 120 000 t yr −1 . Its potential as a major chemical feedstock, derived from renewable carbohydrates by sustainable technologies, to make plastics, fibers, solvents and oxygenated chemicals, had also been recognized. Recently, new technologies have emerged that can overcome major barriers in separations and purification and processing. Advances in electrodialysis (ED) and bipolar membranes and one particular process configuration termed the 'double ED' process, a specific combination of desalting ED followed by 'water-splitting' ED with bipolar membranes, has given very promising results, showing a strong potential for an efficient and economic process for recovery and purification of lactic acid without generating a salt waste. For the production of polymers, several advances in catalysts and process improvements have occurred in the technology to produce dilactide and its polymerization to produce plastics and fibers by Natureworks LLC, which is the leader in lactic polymer technology and markets. Other advances in esterification technology with pervaporation and development of biosolvent blends also have a high potential for 'green' solvents in many applications. Recently, a considerable amount of pioneering effort in technology, product development and commercialization has been expended by several companies. To overcome the barriers to replace long-established petroleum-derived products, further real support from consumer, regulatory and government organizations is also needed.

A variety of test procedures have been reported in the literature for determination of the specific methanogenic activity profile of anaerobic sludges and for screening synthetic organic chemicals for anaerobic biodegradability. This paper reviews the methods developed and presents data obtained in the authors' laboratory using test procedures based on pressure transducer measurement of gas pressures in sealed anaerobic vials. Data on the feasibility of freeze-drying granular sludge are also presented as part of a wider study concerning the development of a standard reference sludge for anaerobic biodegradability testing. The use of the methanogenic activity test method to assess the relative toxicity of compounds, known to inhibit methanogenesis, against individual trophic groups involved in the overall digestion process is also described.

Energy-efficient capture of CO2 from power-plant flue gas is one of the grand challenges to reduce greenhouse gas (GHG) emissions. Current CO2-capture technologies are limited by parasitic energy loss, inefficient capture, and unfavorable process economics. We present a novel electrochemical method for CO2 capture from coal-fired power-plant flue gas. The method utilizes in-situ electrochemical pH control with a resin wafer electrodeionization (RW-EDI) device that continuously shifts the pH of the process fluid between basic and acidic in sequential chambers (pH swing). This pH swing enables capture of CO2 from flue gas in the basic chamber followed by release (recovery) of the captured CO2 (purified) in the acidic chamber of the same device. The approach is based on the sensitivity of the thermodynamic equilibrium of CO2 hydration/dehydration reactions over a narrow pH range. The method enables simultaneous absorption (capture) of CO2 from flue gas and desorption (release) at atmospheric pressure without heating, vacuum, or consumptive chemical usage. In other words, the method concentrates CO2 from ∼15% in flue gas to >98% in the recovery stream. To the best of our knowledge, this is the first experimental study focusing on simultaneous capture and release (recovery) of CO2 using an electrochemical method. We describe the method, the role of operating parameters on CO2 recovery, and advancements in process design and engineering for improved efficiency. We report on a method to enhance gas/liquid mixing inside the RW-EDI, which significantly increased CO2 capture rates. We also discuss the importance of using an enzyme/catalyst in enhancing the reaction kinetics. CO2 capture was observed to be a strong function of gas and liquid flow rates and applied electrical field. Up to 80% of the CO2 was captured from a simulated flue gas stream with >98% purity. The results indicate that a narrow pH swing from 8 to 6 (near-neutral pH) could offer a viable pathway for energy-efficient CO2 capture if the reaction kinetics are enhanced. Carbonic anhydrase enzyme enhances the reaction kinetics at near-neutral pH; however, the enzyme lost activity due to the instability at the operating conditions. This observation highlighted the necessity of robust enzymes/catalysts to enhance kinetics of CO2 recovery near-neutral pH.

The equilibrium constants for ring-chain tautomerism in a series of cis-3-acylacrylic acids have been determined by using the observed pK, and true pK, (pKST) values in 80% (w/w) 2-methoxyethanol-water. The latter were estimated from the relation between pK, values of a series of cis-and rrans-3-substituted acrylic acids. The results are discussed.EARLIER investigations 2-4 demonstrated the occurrence of ring-chain tautomerism in cis-3-acylacrylic acids, (I). and ( 11), as shown in equation (1). No quantitative studies of these equilibria appear to have been madeRecently, quantitative investigations of this tautornerism in 2-benzoylbenzoic 596 and cis-3-aroylacrylic acids have been described. The qualitative evidence 2-4 regarding the cis-3-acylacrylic acids indicates that these compounds exist predominantly as the ring isomer. The equilibrium constants, Kc, are given by the relation (2). Ke = aRinglaChain(2) The observed pK, can be related to the true pK,T by the relation (3). If a reliable estimate of pKaT can be P K T = pKalog (Ke + 1)(3) made, K , can be found by measuring the observed pK,.In the present study, we have investigated the ionisation of a series of cis-and trans-3-substituted

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