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    Application of pyrrolidinomethylcalix[4]arene coated silica adsorbent for the removal of Chicago sky blue 6B dye from water samples: Equilibrium and computational modelling studies
    (Taylor & Francis Ltd, 2021) Junejo, Ranjhan; Jalbani, Nida Shams; Kaya, Savas; Erkan, Sultan; Ebenso, Eno E.
    In this study, silica surface has been coated using pyrrolidinomethylcalix[4]arene through the chemical modification of silanol groups. The pyrrolidinomethylcalix[4]arene-coated silica (PCS) adsorbent was characterized using the Fourier transform infrared and scanning electron microscopic technique. The adsorptive removal efficiency of PCS adsorbent was checked through batch studies with various effective parameters such adsorbent dose, pH, and temperature. During experiments, it has been observed that maximum adsorption was achieved in acidic to neutral pH and 25 mg.L-1 of PCS dose, while the kinetic models demonstrates that the pseudo 2nd order equation was the best fit (R-2 0.99). The thermodynamic experiments described that the reaction is exothermic and spontaneous. Furthermore, equilibrium models were applied on experimental data and it has been noticed that the equilibrium data was best-fitted with Langmuir isotherm model (R-2 0.99). The DFT analysis of dye molecule is helpful to examine the chemical interaction sites of absorbent and adsorbent using B3LYP/LANL2DZ/6-311++G (d,p) level using G09W software.
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    Effective Removal of the Direct Black-38 Dye from Wastewater Using a New Silica-Modified Resin: Equilibrium and Thermodynamics Modeling Studies
    (Amer Chemical Soc, 2020) Junejo, Ranjhan; Memon, Shahabuddin; Kaya, Savas
    In this study, the synthesis of p-diethanolaminomethylcalix[4]arene and its immobilization on a silica surface have been performed for the removal of the direct black (DB-38) dye from wastewater samples. The newly synthesized p-diethanolaminomethylcalix[4]arene-immobilized silica (DIS) resin has been analyzed and characterized by FTIR spectroscopy and SEM techniques. To check the efficiency of the DIS resin, batch and column adsorption procedures have been applied under the optimized parameters, i.e., resin dosage, pH, and temperature. To validate the experimental data, Langmuir, Freundlich, and D-R models have been applied. The results show that adsorption follows the Freundlich model well with a good correlation coefficient (R-2 = 0.999). Moreover, the energy E (kJ/mol) was calculated with the help of the D-R model, which suggested that the adsorption has an ion exchange nature. The DIS resin was also applied to real industrial samples of DB-38 dye wastewater. The results show that the DIS resin removes 99% of the dye successfully. Thermodynamics studies were conducted to know the feasibility and the mechanism of the adsorption reaction. The thermodynamic parameters show that the adsorption is spontaneous and exothermic. The theoretical calculation was performed at the B3LYP/DZP calculation level of the ADF program, and the power of the interaction between adsorbent and dye molecules can be determined in the light of chemical reactivity analysis.
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    Equilibrium, thermodynamic, and kinetic modeling studies for the adsorptive removal of oxyanions from water
    (TAYLOR & FRANCIS INC, DEC 2021) Elik, Mustafa; Junejo, Ranjhan; Jalbani, Nida Shams; Kaya, Savas; Serdaroglu, Goncagul; Memon, Shahabuddin
    Water is being contaminated by different oxyanions which have many negative effects on the human body. This study deals with the adsorptive removal of Cr2O7-2, AsO4-3, and ClO4-1 oxyanions from water using diethanolaminomethylcalix[4]arene bonded silica (DBS) resin. The capacity of DBS resin for the removal of oxyanions was checked through batch method under the optimized parameters such as pH, adsorbent dosage, concentration of oxyanions, and effect of temperature. The experimental data were analyzed through Langmuir, Freundlich, and Dubinin-Radushkevitch (D-R) adsorption isotherm models and the Langmuir model was the best fit model with a good correlation coefficient (R-2 0.998). The thermodynamic and kinetic studies were performed to check the mechanism and adsorption pathway of oxyanions onto DBS resin. The thermodynamic parameters such as (Delta H degrees, Delta S degrees, and Delta G degrees) describes that the adsorption of oxyanions was spontaneous and endothermic and followed by pseudo second order kinetic models very well. The reusability of resin was also checked and it has been observed that after 27 cycles only 2% loss in adsorption capacity. Moreover, the oxyanions were optimized at the B3LYP/LANL2DZ/6-311++G (d,p) level using G09W software to analyze the oxyanions-DBS interactions phenomenon.