Neetu Singh

Growing demand for sustainable solvents has considered deep eutectic solvents (DESs) as promising alternatives to conventional organic solvents. In this work, a DES composed of ethylene glycol and choline chloride at a molar ratio of 2:1 (EC2:1) was synthesized and studied as an entrainer for the separation of the acetonitrile (ACN)-water azeotrope. VLE measurements were carried out using an improved Othmer recirculation still under ambient conditions. First, measurements were carried out for the pseudobinary systems comprising EC2:1 + water and EC2:1 + ACN. Subsequently, for the pseudoternary system EC2:1 + ACN + water at 5%, 10% and 12 mol % DES concentrations. Increasing EC2:1 concentration progressively enhanced the relative volatility of ACN by lowering water activity through preferential EC2:1–water interactions and a salting-out effect, the azeotrope persisted at 5 mol % EC2:1 but was eliminated at 10 mol %. The experimental VLE data were validated using the NRTL activity coefficient model. The low mean absolute deviations of 0.17–0.44 K in equilibrium temperature and 0.006–0.008 in vapor-phase ACN mole fraction demonstrate good agreement between the experimental data and the NRTL model predictions. Moreover, the systematic evaluation of recovery and reusability of EC2:1 confirmed its high effectiveness and recyclability for the separation of the ACN-water azeotropic mixture.

In this work, the linearity axiom of irreversible thermodynamics for diffusion and heat transfer has been re-examined. It is shown that this axiom is compatible with the entropy production invariance principle with respect to a reference quantity for diffusion and heat transfer in the Euclidean space. Moreover, the underlying relations of the other principles of irreversible thermodynamics for multi-component diffusion and heat transfer, such as the quasi-equilibrium and the Onsager reciprocal relations (ORR) with the entropy production invariance, are re-examined. It was shown that the linearity principle postulates for diffusion and heat transfer and could be directly derived from the entropy production invariance axiom. It is believed that this work could not only be used for the drying of polymer coatings but also for pedagogical purposes. It may also be generalized; thus, leading to a generalized framework for irreversible thermodynamics.

This work investigates the competitive adsorption of ofloxacin (OXC) and doxycycline (DCL) form OXC-DCL binary solution on to MCM-41, not reported earlier. Experiments were conducted at 288–318 K temperatures, and equilibrium adsorption isotherm data were analysed to study the competitive effect of the presence and absence of DCL on OXC adsorption and vice-versa in OXC-DCL binary solution. On this basis, the competitive interaction, Synergistic, Antagonistic and No interaction effects, for OXC and DCL adsorption was evaluated. Furthermore, the experimental equilibrium adsorption data were used for isotherm modelling using various multi-component competitive isotherm models such as extended Langmuir, extended Freundlich and Sheindorf–Rebuhn–Sheintuch (SRS) isotherms. It was found that single component adsorption for OXC, and OXC adsorption in the presence of DCL and vice-versa followed Freundlich and extended Freundlich isotherm model, respectively. The competitive adsorption interaction between OXC and DCL from their binary solution was found to be antagonistic at all temperatures.

Electrocatalytic oxidation (EO) of carcinogenic 4‐aminobiphenyl (4‐ABP) aromatic amine was performed using Ti‐RuO₂ anodes. Current (I), pH, electrolysis time (t), and 4‐ABP initial concentration (C_o) were selected as EO parameters, and their effects on %4‐ABP removal (R₁) and energy consumed (R₂) were studied. Experimental design, parameters optimization, and their interaction with responses R₁ and R₂ were performed using response surface methodology. At optimized parameters, %TOC removal and 4‐BP mineralization current efficiency (%MCE) were assessed to evaluate the potential of Ti/RuO₂ anodes towards 4‐ABP mineralization. Simultaneous TOC and 4‐ABP degradation kinetics were also studied to evaluate the competition in 4‐ABP mineralization and degradation. Further, UPLC‐Q‐TOF‐MS analysis was performed to identify the 4‐ABP transformation products during the EO, and a mechanism describing the EO transformation was proposed. At optimum parameters (I = 1.2 A; pH = 4.0; t = 30 min; C_o = 30 ppm), responses were found to be R₁ = 60.25%; R₂ = 2.49 kWh/g of 4‐ABP removed. %TOC removal and %MCE were 52.4% and 34.2%, respectively.Practitioner Points: 4‐Aminobiphenyl electro‐oxidation (EO) was explored using Ti/RuO₂ anode. Achieved 34.2% mineralization current efficiency, 52.4% TOC and 61.3% TKN removal. Three electro‐oxidation transformation products of 4‐ABP were detected. 4‐Aminobiphenyl was found degrading at ≈1.6 times higher rate than TOC A plausible EO transformation pathway and mechanism was proposed.

Antibiotics are bio-accumulating and persistent. its inappropriate disposal can affect human health and aquatic fauna. Development of antimicrobial resistance has been announced as one of the top ten threats to global health in 2019. In this study, Doxycycline adsorption on to MCM-41 (not reported earlier) was studied. Adsorbent dose (m), Doxycycline solution pH, adsorption time (t) and temperature (T) were considered as process parameters, and %Doxycycline removal and adsorption capacity were measured as responses of the adsorption. Parameters (m, pH and t) interaction, modelling and optimization for %Doxycycline removal and adsorption capacity was performed using Box Behnken Design. Based on this, a suitable model equation and adsorption mechanism was suggested. At optimized parameters, kinetics and adsorption rate controlling mechanism was studied. Further, various isotherm models (Freundlich, Langmuir and Redlich-Peterson) were studied to represent the adsorption equilibrium experimental data. the optimum process parameters were found to be pH = 7.3, m = 0.02 g/L and t = 20 min. At optimized parameters, very high %Doxycycline removal of 99% with 2425 mg/g adsorption capacity was observed (max 835.5 mg/g adsorption capacity for Doxycycline is reported in literature). Thermodynamics study revealed enthalpy (ΔH°) = 23.02 kJ/mol confirming DCL physisorption on MCM-41.

The huge demand and consumption of DOX, its incomplete metabolism, and complex behavior in atmosphere are causing a great ecological issue, which needs to be solved. In the present study, the suitability of rice husk ash (RHA) for the greater sorption efficiency of DOX antibiotic was investigated. Furthermore, disposability study of exhausted RHA was performed using solidification technique and leachate had undergone toxicity test to evaluate the DOX encapsulation ability. The central composite design under RSM was employed for the design of experiment and optimization of adsorption parameters. RHA was characterized using various techniques such as XRD, SEM (EDX), FTIR, BET, and zeta potential analysis. The influence of various adsorption parameters, like initial DOX concentration (C₀), RHA dosage (m), incubation-time period (t), and pH were examined on the performance in terms of DOX elimination % (X₁) and adsorptive capacity (mg/g) (X₂). At optimized conditions, the obtained X₁ and X₂ were 98.85% and 17.74 mg/g, respectively. Moreover, the kinetics data suited well to the pseudo–second-order model. Freundlich, Langmuir, and Redlich-Peterson (R-P) isotherm models were applied, out of which Langmuir model best performed under optimized conditions; m = 5 g/L, t = 85.85 min, DOX concentration = 89.73 mg/L, and pH = 6. The bacterial toxicity test of leachate confirmed complete encapsulation of DOX by solidification technique.