Browsing by Author "Potnuri, R."

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Isoconversional Kinetic Analysis and ANN-Based Prediction of Metformin Pyrolysis for Sustainable Waste Management
(American Chemical Society, 2025) Potnuri, R.; Lenka, M.; Sankar Rao, C.; Harshini, H.
Pharmaceutical waste poses a growing environmental concern due to its persistence and potential ecological impacts, necessitating effective and sustainable management strategies. This study investigates the pyrolysis of metformin as a means to valorize pharmaceutical waste within a circular economy framework. Pyrolysis experiments conducted on 500 mg of metformin demonstrated the formation of liquid-phase products, characterized by GC–MS, which revealed a high concentration of the active pharmaceutical ingredient (API) alongside carbonaceous, nitro, and acidic compounds. Comprehensive thermogravimetric analyses at heating rates of 10, 20, 30, and 40 °C/min were performed to evaluate the thermal decomposition behavior. Kinetic parameters were determined using four isoconversional methods, namely KAS, FWO, Starink, and FRD, yielding average activation energies of 101.4, 105.8, 101.4, and 111.1 kJ/mol, respectively. Thermodynamic parameters (?G, ?H, and ?S) were also calculated to gain further insights into the decomposition process. Additionally, an ANN model was developed using temperature and heating rate as inputs to predict mass loss, achieving accurate estimations with an optimized architecture comprising two hidden layers. GC–MS analysis of the pyrolysis liquid identified a high concentration of the API, along with carbonaceous, nitro, and acidic compounds. These findings highlight the potential for API recovery and reuse, as well as the valorization of byproducts for energy or chemical synthesis. The potential recovery of APIs for reuse and the utilization of byproducts as fuels or chemical precursors underscore pyrolysis as a promising route for sustainable pharmaceutical waste management and circular economy integration. © 2025 The Authors. Published by American Chemical Society
Synthesis and Characterization of Biochar Obtained from Microwave-Assisted Copyrolysis of Torrefied Sawdust and Polystyrene
(American Chemical Society, 2024) Potnuri, R.; Sankar Rao, C.
This study focuses on copyrolyzing pretreated sawdust and polystyrene utilizing microwave-assisted pyrolysis (MAP) with equal mixing to synthesize and characterize biochar. Graphite was used as a susceptor to facilitate precise pyrolysis temperature control. Potassium hydroxide (KOH) powder serves as a catalyst, influencing the char yields and properties. Torrefied raw sawdust at various temperatures (125–175 °C) enhances biochar yields (24–29 wt %). The feedstocks sawdust and polystyrene are characterized by elemental, proximate, and TGA examinations. Furthermore, comprehensive surface, crystallographic, FTIR, and SEM-EDX analyses are performed on microwave copyrolyzed biochar. The developments in BET surface area during copyrolysis show changes concerning pretreatment temperatures: 125 °C (5.6 m2/g) < 150 °C (6.8 m2/g) < 175 °C (8.6 m2/g). Functional groups connected to the alcohols’ O–H bend and C–O stretching vibrations are detected in the biochar samples through FTIR analysis. Sharp peaks with 2θ values between 33.2° and 36.2° appear in the XRD scan of biochar, indicating the presence of crystalline components in the sample. The EDX results demonstrated that the components of biochar included Mg, C, O, and Ca, indicating that it could have plenty of advantageous applications. The study highlights the obstruction of sawdust char’s porous structures by polystyrene, hindering volatile emissions and leading to increased heating rates. These findings underscore the unique contributions of this method to biochar production. © 2024 American Chemical Society
Ultra-high ammonia gas response of phase-stabilized (Fe0.2Ni0.2Cr0.2Mn0.2Zn0.2)3O4-? high-entropy spinel oxide sensor array and its machine learning predictions
(Elsevier Ltd, 2025) Praveen, L.L.; Upadhyay, B.; Potnuri, R.; Mandal, S.
In this work, the gas sensing performance of phase-stabilized (FeNiMnZnCr)3O4 high-entropy spinel oxide (HSO) gas-sensors via screen-printing were investigated, where the HSO powders were synthesized via solution combustion synthesis (SCS) using three different fuels: citric acid, urea, and glucose. Although all HSO powders were obtained at 500 °C, the formation of stable spinel phase was evidenced at 600 °C. Among all fabricated sensors, G-800 gas sensor depicted a stable ultra-high response of ?3471 towards 100 ppm of ammonia gas along with a notable response of ?162 even at 10 ppm (where G means glucose and 800 represents calcination temperature in °C) and it demonstrated a strong device-to-device reproducibility with stability of ?35 days. A synergy of crystallinity and increased porosities from XRD and FESEM micrographs resulted in ultra-high gas-response towards ammonia gas compared to volatile organic compounds such as formaldehyde, methanol, and ethanol). The presence of defect band and oxygen vacancies observed from the Raman and XPS analysis, were complemented by the presence of porosities confirmed from BET surface area analysis. Subsequently, the machine learning (ML) algorithms are applied on sensor signals to estimate the concentration of ammonia gas, and among all the ML classifiers, RFC gave reasonably better predictions in three concentrations regimes with a good classification accuracy of 93.3 ± 5.3 %, 90 ± 7.5 %, and 83.3 ± 13.1 % for G-600, G-700, and G-800, respectively. The proposed ML studies enable accurate detection of hazardous ammonia levels using HSO-based sensors, showing strong potential for integration into diagnostic platforms targeting ammonia breath markers. © 2025 Elsevier B.V.