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In this study, we present the synthesis of gold nanoparticles (AuNPs) using a completely green synthesis method without the use of any additional functionalizing agent, except dried turmeric root extract. The significant synthesis parameters were optimized, and the applicability of AuNPs was investigated in areas such as plasmonic and fluorescent sensing of aluminum (Al3⁺) and chromium (Cr3⁺) ions, reduction of 4-nitrophenol (4-NP), and degradation of methylene blue (MB) and methyl orange (MO) dyes. Characterization studies were performed using UV–Vis spectroscopy, TEM, FTIR, and XRD, revealing that the AuNPs predominantly had a spherical morphology and a very small particle size of 8.5 nm, with stability maintained up to 120 days. The developed AuNP-based plasmonic sensors relied on aggregation-induced decreases in absorption, along with a red shift in the spectra. Fluorescence sensing demonstrated a linear increase in intensity with increasing concentrations of Al3⁺ and Cr3⁺, with detection limits of 0.83 and 1.19 nM, respectively. The catalytic activities of AuNPs were tested in reducing 4-NP and degradations of MB and MO dyes (binary system) in tap water and wastewater, with the reactions following pseudo-first-order kinetics. This study highlights the potential of AuNPs synthesized from turmeric roots for various environmental and sensing applications. [ABSTRACT FROM AUTHOR]

In this study, biochar was obtained from walnut shells (WS) using one- and two-stage pyrolysis processes at different temperatures (500, 600, 700, 700 + 700 °C). The biochar obtained was used as an adsorbent for the removal of naproxen, an organic pollutant, from aquatic systems. The highest removal efficiency was obtained with 700 + 700-WSB obtained by the two-stage pyrolysis method. The physicochemical properties of walnut shell biochar (WSB) were investigated using SEM–EDX, FTIR, XRD, BET, elemental analysis, and TGA. 700 + 700-WSB had a high surface area of 649 m2/g and a pronounced porous structure, according to the BET and SEM analysis results. Various experimental parameters (pH, contact time, amount of adsorbent, temperature, initial concentration, and pHpzc) were investigated to study the adsorption of naproxen by 700 + 700-WSB in an aqueous solution. The point of zero charge of the 700 + 700-WSB adsorbent was calculated as 7.15. The 700 + 700-WSB obtained at optimum parameter levels, such as 25 °C and 4 h time has an adsorption capacity of 58.8 mg/g. To analyze the equilibrium results, the Langmuir, Sips, Freundlich, and Temkin adsorption isotherm models were utilized. The equilibrium data fit the Langmuir (R2 = 0.984) and Sips (R2 = 0.979) models among the isotherm models. Investigating the adsorption characteristics of naproxen on WSB involved the study of the kinetic models and thermodynamic components of the adsorption process. The psuedo-second order kinetic model (PSO) was shown to be consistent with the experimental data through kinetic investigations, and the thermodynamic results (ΔG° = − 21.87 kJ/mol, ΔH° = − 29.52 kJ/mol and ΔSº = − 25.73 J/mol K) indicated that the adsorption process was exothermic and spontaneous. [ABSTRACT FROM AUTHOR]

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BACKGROUND Low‐cost biosorbent (derived from peanut shells) with abundant oxygen‐containing functional groups can effectively adsorb the naproxen drug in solution. This study aimed to explore the main interactions responsible for adsorbing naproxen and develop several conventional methods for identifying primary adsorption mechanism. Some important operation parameters strongly effecting the adsorption process and mechanism were investigated and discussed. RESULTS: A fast adsorption equilibrium can be reached at approximately 120 min. The Langmuir maximum adsorption capacity of biosorbent towards naproxen (Qomax; mg g−1) was 55.1 mg g−1. The study of adsorption thermodynamics indicated that the adsorption process was spontaneous (∆G° ≈ −21 kJ mol−1) and exothermic (∆H° = −14.9 kJ mol−1), and van der Waals force played an important role in the adsorption mechanism. Another important contribution of n–π interaction between the carbonyl groups on the biosorbent's surface and the aromatic rings in naproxen molecules was confirmed by Fourier‐transform infrared spectroscopy and a traditional method. Such n–π interaction cannot be well performed when carbonyl groups were oxidized into carboxylic groups under H2O2 treatment. Peanut shells exhibited an excellent adsorption capacity to various pollutants such as lead (Qomax = 167 mg g−1), cadmium (103 mg g−1), cobalt (88.8 mg g−1), diclofenac (56.1 mg g−1), and bisphenol A (24.5 mg g−1). CONCLUSIONS: Simple methods were developed to identify the important role of van der Waals force and n–π interaction in the adsorption process of naproxen. Such methods might be applied to identify the similar adsorption mechanisms of other aromatic adsorbates onto other materials with similar properties. Peanut shells can serve as a promising biosorbent for eliminating naproxen and other pollutants from water environment. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Pb(II) ions were separated/preconcentrated and detected by a two-step preconcentration method (Amberlite CG-120 resin and slotted quartz tube (SQT) flame atomic absorption). The first preconcentration step was the adsorption of Pb(II) on Amberlite CG-120 resin in the drinking, spring and lake water samples before detection and then its elution using 5 mL of 3 M nitric acid. The second preconcentration step was conducted using SQT device with flame atomic absorption detection. Using a two-step preconcentration method, enrichment factor of 560 was found and detection and quantitation limits were 0.23 and 0.8 µg/L, respectively. The accuracy of the method was tested by analysis of standard reference material (Environmental Matrix Reference Material, Lake Water, TMDA-70.2) at a 95% confidence level. [ABSTRACT FROM AUTHOR]