Purification of Lactic Acid via Esterification of Lactic Acid Using a Packed Column, Followed by Hydrolysis of Methyl Lactate Using Three Continuously Stirred Tank Reactors (CSTRs) in Series: A Continuous Pilot Plant Study

The world market of lactic acid is growing every year, mainly as a solvent and precursor to poly(lactic acid) (PLA). The cost of renewable biomass-derived PLA will have to compete with other synthetic polymers, if it is to grab a significant and sustainable fraction of the market share. It is thus necessary to have efficient and cost-effective technology for the production of pure-grade lactic acid (LA). In this article, a novel cost-effective, eco-friendly continuous process for the production of high-quality lactic acid at pilot plant scale has been demonstrated. The novelty of this process is that, for the first time, we report and use the concept of inverse reactive distillation for the esterification of crude concentrated LA in a continuous countercurrent packed column mode. This allows us to operate the column at higher temperatures, improving the kinetic rate process and leading to shorter columns. This is followed by the hydrolysis of methyl lactate (MLA) in a series of three continuously stirred tank reactors (CSTRs), where LA itself acts as a catalyst. The LA obtained in the pilot plant process shows 99.81% purity (by weight) on water-free basis and has an optical purity of 99.9%. The pilot scale experimental results pertaining to the autocatalytic esterification of LA and hydrolysis of MLA have been compared and validated, with respect to simulated results. The innovations reported here can make the process economically viable for commercial use

Photocatalytic Degradation of Pharmaceuticals Pollutants Using N-Doped TiO₂ Photocatalyst: Identification of CFX Degradation Intermediates

<p>The N-doped TiO₂ photocatalyst was synthesized by the sol–gel method and characterized in detail in terms of its morphology, structure and composition. The prepared N-doped TiO₂ exhibited polycrystalline structure having particle sizes of around 50–120 nm and rod-shaped geometry. The N-doped TiO₂ was subsequently used for the photocatalytic degradation (PCD) of pharmaceutical micropollutants, namely ciprofloxacin HCl (CFX), naproxen (NPX) and paracetamol (PARA) and it was found that the rate of degradation of CFX and NPX is higher than that of PARA. To verify the beneficial effect of N-doped TiO₂ for PCD of CFX, similar experiments were carried out using commercially available Aeroxide P-25 TiO₂. It was observed that N-doped TiO₂ was more efficient than Aeroxide^® P-25 TiO₂. It was also found that the PCD of CFX in the presence of N-doped TiO₂ was highly efficient under the solar radiation as compared with artificial radiation. The effect of various operating parameters, such as adsorption of CFX, pH of the aqueous solution, effect of co-existing ions on PCD of CFX, was investigated using artificial radiation and optimum conditions were established. The intermediates formed during the PCD of CFX were identified using liquid chromatography tandem mass chromatography (LC-MS/MS). The presented results demonstrate that N-doped TiO₂ photocatalyst shows excellent photocatalytic activity in the visible region for the degradation of pharmaceutical pollutants.</p