Characterization of Sonochemical Reactor for Physicochemical Transformations

Abstract

Complete knowledge of the pressure field distribution in a sonochemical reactor should be known for an efficient utilization of acoustic energy emitted by the transducers for targeted physicochemical transformations using cavitation phenomena. This work deals with the identification of the active and passive regions in the sonochemical reactor based on the measured pressure field intensities. Iodine liberation experiments based on the decomposition of aqueous potassium iodide (KI) as a representative of cavitationally induced chemical transformation were carried out at various locations in the bath type reactor and compared with the measured pressure intensities in the reactor. Similarly, extraction of natural dye from the bark of Pterocarpus marsupium tree has also been carried out as a representative of cavitationally induced physical transformation (extraction) and compared with the measured pressure intensities. Both the transformations indicate a similar trend of variation in the degree of transformation when correlated with the local pressure and indicated the existence of an optima, which is at a plane (≈3λ/2) away from the transducer surface.

A New Insight into Non‐Steroidal Anti‐Inflammatory Drugs (NSAIDs) as Modulated Green Inhibitory Agent on Mild Steel Corrosion

“…The influence of the drug in various concentrations on the metal loss in MS corrosion has been investigated depending on the limit of its solubility in water at that temperature and the concerned parameters are depicted in Table 1. [5,18] It is clearly seen that the %IE of inhibitor increases and CR decreases with increase in the NSAIDs concentration. Such behaviour could be inferred to the decrease in the weight loss due to the increase in adsorption of inhibitor onto the substrate interface.…”

“…[6] In addition to the chemical adsorption, reported studies have shown that the inhibitor molecules do exhibit electrostatic interaction between the charged metal surface and inhibitor. [18] After 4 h of MS immersion in the aggressive acidic environment, it could be seen from Figure 1 that the positively charged NSAIDs molecules get adsorbed on negatively charged MS surface. Thus forming Fe-NSAIDs complexation resulting in a protective layer.…”

“…Thus forming Fe-NSAIDs complexation resulting in a protective layer. [13,18,19] Based on the nature of the electronic absorption bands, it was seen that the drug solution before and after MS immersion show variations in the absorbance i. e., bands: 235 nm and 300 nm for Aspirin (π-π* and n-π* transition due to presence of ester and carboxylic group), 276 nm and 225 nm for Diclofenac (n-σ* transition due to CÀ Cl and -NH-present) and 263 nm for Ibuprofen (σ-σ* transition occur due to alkane substitution). Amongst these drugs the performance of the Aspirin was seen noticeable which could be attributed to the respective transitions with a considerable charge transfer characteristic which is not observed in the rest drugs which proves the former to undergo better interactions with the MS surface leading to the feasible of Fe-NSAIDs complexation with higher corrosion inhibition efficiency than the later.…”

“…I corr values were found decreasing with increase in concentration without causing any significant changes there by suggesting that the existence of drugs retard the electrochemical reaction on MS surface due to the protective (barrier) layer of NSAIDs on MS surface which increases %IE. [16,18,[24][25][26] Apparently from Figure 2, the nature of the polarization curves remained the same in the absence and presence of NSAIDs. However, a shift in the curves towards lower value of current density in presence of NSAIDs was observed, thereby showing CR retardation.…”

“…Such trend is a typical characteristic of the solid electrode, indicating frequency distribution of impedance data. [18,25] The low-frequency inductive loop is because of relaxation process obtained by the adsorbed species (Cl À ads and H + ads ) on the electrode surface which could be due to non-dissolution of the passivated surface at low frequencies. [10] The relaxation time (τ) of any metal surface is given by ζ = C dl .…”