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In this study, a new efficient resin-based material has been synthesized through the surface modification of silica by functionalized calix[4]arene and applied for the adsorption of metal ions from aqueous media. The synthesis of functionalized calix[4]arene modified silica (FCMS) resin was characterized by FTIR, CHNS, BET surface area, SEM analyses. The FCMS resin has high thermal and chemical stabilities that were checked by the thermogravimetric analysis and various acidic/basic conditions. The efficiency of the FCMS resin was checked by performing a set of batch experiments under optimized parameters such as concentration of the metal solution, pH, resin dosage, time, temperature, and competitive adsorption in mixed solutions. The results showed that better adsorption has been achieved at pH 7, with 25 mg adsorbent dosage and 10 min contact time. The equilibrium kinetic study showed that the metal adsorption follows the pseudo 2nd order kinetic model with quite high coefficients of determination values (R-2 > 0.99). The experimental data have been validated by applying three adsorption isotherm models and the results revealed that the Freundlich isotherm model (R-2 > 0.99) was the best fit for the adsorption of Cu2+, Pb2+, and Cd2+ ions. However, the sorption energy calculated from the D-R isotherm model for Cu2+, Pb2+, and Cd2+ ions suggested that an ion-exchange mechanism is involved on the surface of the FCMS resin. The thermodynamic data demonstrated that the reaction is spontaneous and endothermic. The FCMS resin was also applied on real wastewater samples and the results demonstrated that the resin has a good ability to treat metal-contaminated wastewater. (C) 2021 Elsevier B.V. All rights reserved.

KEYWORDSCalixarene;Immobilization;Silica resin;Direct azo dye;Solid-phase extraction;Batch-wise sorptionAbstract The present study demonstrates the adsorption of the direct black-38 (DB-38) azo dye onpotential and newly synthesized p-tert-butylcalix[6]arene based silica resin (4). Resin 4 was synthe-sized via the modification of pure silica 1 as 2 followed by the immobilization of p-tert-butylca-lix[6]arene (3) onto modified silica (2). It was characterized by using different analyticaltechniques such as FT-IR, scanning electron microscopy (SEM) and thermo gravimetric analysis(TGA). The effect of adsorbent dosage, pH and the electrolyte effect on the removal of the DB-38 azo dye were evaluated through batch wise adsorption experiments. Maximum adsorption of91% was achieved at pH 9.0. The textile wastewater samples were used to ensure the field applica-bility of the newly synthesized adsorbent 4 for the treatment of dye contaminated effluents. Allresults regarding the removal of the DB-38 azo dye from the aqueous environment prop up resin4 as an effective adsorbent and it was found that resin 4 has high adsorption efficiency towardthe DB-38 azo dye at a wide range of pH as compared to 1 and 2.a 2013 Production and hosting by Elsevier B.V. on behalf of King Saud University.

The determination of cefixime 1 has clinical and analytical importance due to its broad spectrum antimicrobial activity and stability. Cefixime is a significant member of orally active third generation cephalosporin and has excellent activity against many pathogens. It is for first time that we have developed a new HPLC-DAD method for analysis of imine derivative 3 of cefixime by using reflux method at 100 °C for 50 min without any buffer solution. 2 Thiophenecarboxaldehyde (2TCA) 2 was used first time as a derivatizing reagent for cefixime drug. Furthermore, separation of three components, i.e. drug (cefixime), reagent (2TCA) and derivative was carried out using kromasil 100 C-18 (15 mm × 0.46 mm, 5 μm) column with isocratic elution of methanol: 0.1% aqueous formic acid (70:30 v/v) with flow rate of 1 ml min(-) (1) at retention time of 1.8, 2.4 and 3.3 min, respectively; while, total run time was 5 min. The developed method was repeatable with a relative standard deviation (RSD) of 0.81-1.88% for imine derivative. The limit of detection and quantification of imine derivative 3 were obtained within the range of 0.132-0.401 μg ml(-) (1) and compared with cefixime drug as 0.30-0.90 μg ml(-1), respectively. However, the formation of imine derivative 3 was confirmed by comparing peak height, retention time and spectral changes. The method is rapid, simple, very stable and accurate for the separation and determination of imine derivative 3 of cefixime 1.