Central Salt and Marine Chemicals Research Institute (formerly Central Salt Research Institute) is a constituent laboratory of the Council of Scientific and Industrial Research (CSIR), India. The institute was inaugurated by Jawahar Lal Nehru on 10 April 1954 at Bhavnagar, in Gujarat.
The overarching demand for green energy has led to the increased use of lithium-ion batteries (LIBs), resulting in a surge of spent LIBs and critical metal waste. This study introduces a sustainable approach for metal recovery using recyclable hydrophobic deep eutectic solvent (HDES) composed of 1-butyl-3-methylimidazolium chloride and oleic acid (1:1 molar ratio). The HDES effectively leaches lithium (Li) and manganese (Mn) from lithium manganese oxide (LMO) cathodes under mild conditions, offering an eco-friendly alternative to conventional acid-based treatment. A single-step leaching process followed by oxalic acid precipitation enabled efficient metal separation. Kinetic modeling indicated that both diffusion and surface chemical reactions govern the leaching rate, with calculated activation energies of 24.08 and 30.32 kJ mol−1 for Li and Mn, respectively. Lithium recovered as high-purity lithium carbonate, and manganese as manganese oxalate, verified by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) and powder X-ray diffraction (PXRD) analysis. The HDES was successfully regenerated using dilute acid, maintaining leaching efficiency across cycles. This green recycling route demonstrates a viable approach for recovering critical metals from LIB waste, aligning with environmental sustainability goals.
Hydrophobic membranes are widely used in various separation processes, including membrane distillation (MD). Previous studies have proposed several simple and cost-effective methods for characterizing such membranes, including the use of the Cassie-Baxter (CB) equation to estimate surface porosity from apparent contact angle measurements-particularly for polyvinylidene fluoride (PVDF) membranes. However, a critical review of the theoretical basis of the CB equation raises concerns about its reliability for this purpose. To investigate its applicability, we compiled literature data and conducted experimental characterization of membranes made from three materials: PVDF (both fabricated and reported), and commercially obtained polytetrafluoroethylene (PTFE) and polypropylene (PP). Our analysis revealed that the surface porosity estimated using the CB equation closely matches the actual value at higher apparent contact angles and observed surface porosities. This is because, at higher apparent contact angles (>= 150 degrees), the membrane surface is more likely to exist in a stable CB state, which aligns with the assumptions of the CB equation used for finding surface porosity (error of up to similar to 15%). In contrast, for membranes exhibiting lower apparent contact angles (<= 130 degrees), the calculated surface porosity values showed significant scatter and deviation (error of up to similar to 49%) due to partial or complete wetting of the membrane, leading to an intermediate state transition between the CB and Wenzel states. These findings reflect studies on PVDF, PTFE, and PP membranes, showing that calculating surface porosity using the CB equation can lead to errors. Therefore, it should be applied with caution and only when there is clear evidence of a stable CB state; otherwise, it may produce false and erroneous results.
In this study, a series of PAN-based poly(acrylonitrile-co-sodium styrene sulfonate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) terpolymer cation exchange membrane (CEM) were synthesized via free radical polymerization. The resulting terpolymers were characterized for their chemical and structural features via NMR, FTIR, and XPS analysis. Terpolymer based membranes were prepared by solution casting and evaluated for their physicochemical, and electrochemical properties. Among the synthesized membranes, PSA-CEM-2.5 exhibited the high ion exchange capacity (IEC) (1.69 meq g(-1)), excellent ionic conductivity (kappa(m)) (11.74 x 10(-2) S cm(-1)), superior transport number (t(+)(m))( (0.94) and permselectivity (P-s) (0.90). Prepared membranes were evaluated for their salt removal efficiency for brackish water desalination by Electrodialysis (ED). PSA-CEM-2.5 membrane achieved the highest salt flux (J) (14.27 x 10(-5) mol m(-2) s(-1)), salt removal efficiency (R-w) (96.08%), lowest energy consumption (EC) (1.02 kWh kg(-1)), and highest current efficiency (CE) (89.30%) among the membranes during brackish water desalination. The membrane also demonstrated good thermal, oxidative, and acidic stability. Artificial neural network (ANN) modeling effectively predicts the performances of all the prepared membranes with high accuracy (>0.98). These findings underscore the potential of PAN-based terpolymer membranes as cost-effective and high-performance alternatives for energy-efficient water desalination.
Thermogravimetric analysis of Persea americana seed powder (PASP) biomass was investigated at heating rates of 5, 10, 20, and 40 °C min-1 under an inert atmosphere to evaluate its thermo-chemical conversion behavior and pyrolysis kinetics. Two major mass-loss stages were observed between 300 and 1023 K, with the principal decomposition occurring between 450 and 600 K. The activation energies were determined using the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink iso-conversional methods, yielding average values of 191.8, 202.7, and 202.2 kJ mol-1, respectively. The adsorption performance of PASP-biochar was evaluated for the simultaneous removal of Cd2+, Zn2+, Ni2+, Cu2+, Pb2+, Hg2+, and Co2+ from aqueous solution. The biochar exhibited good adsorption performance over a wide pH range, followed pseudo-second-order adsorption kinetics, and retained high removal efficiency after regeneration, indicating good reusability. Furthermore, preliminary techno-economic analysis confirmed that PASP-biochar can be produced economically, highlighting its practical potential as a sustainable adsorbent. Overall, this study demonstrates an integrated approach that combines thermo-chemical conversion, kinetic evaluation, and environmental application of avocado seed-derived biochar, providing an effective strategy for agro-waste valorization and sustainable heavymetal remediation from contaminated water.
