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This article describes the preparation of calix[4]arene-bonded silica gels ( C[4]BS and DMC[4]BS ), and their application to the removal of some selected phenolic compounds such as phenol (PHE), p -chlorophenol (PCP), m -nitrophenol (MNP) and p -nitrophenol (PNP) from aqueous solutions by adsorption method. In initial adsorption experiments appeared that C[4]BS was much more effective in adsorption of PNP rather than PHE, PCP and MNP, whereas DMC[4]BS exhibited too little adsorption ability towards all phenols. Herein, it was concluded that the hydrogen bonding capacities of both phenols and calix[4]arene based adsorbents played a predominant role in the interactions between adsorbate and adsorbent within the adsorption mechanism. Thus, in subsequent studies, the C[4]BS was employed as an adsorbent in the adsorption of PNP, and adsorption conditions were optimized. Furthermore, isotherm and kinetic studies were performed to clarify the phenomena of PNP adsorption onto C[4]BS . [ABSTRACT FROM AUTHOR]

This study describes the preparation of a new polymeric calix[4]arene derivative and its application as a sorbent material in adsorption of p-nitro phenol (PNP). Thus after the preparing of the precursor calixarene derivatives (1-5), compound 5 was immobilized onto aminopropyl silica gel supporting material to obtain polymeric calix[4]arene (6). All compounds were characterized by using some methods such as FTIR, ¹H NMR, elemental analysis, TGA and SEM. Aminopropyl silica gelimmobilized calix[4]arene (C[4]APS) 6 was used as a sorbent in the adsorption studies of PNP and it was examined some parameters such as pH, contact time, initial concentration, process temperature and sorbent dosage. The results showed that pH 6, contact time 1 hour, the concentration of 5.0x10-5 M PNP, 0.025 g of sorbent dosage and 25°C of temperature was found as optimum parameters of PNP adsorption by 6. Also Langmuir and Freundlich isotherms were evaluated to clarify the PNP adsorption mechanism. [ABSTRACT FROM AUTHOR]

• The diacid calix[4]arene derivative tethered silica (DACTS) was successfully prepared and applied to remove VOCs. • The RSM and BBD optimization technique was applied to specify the maximum adsorption capacity. • The adsorption of xylene and toluene gases was investigated in terms of kinetics and isothermal conditions. • The maximum adsorption uptake of xylene and toluene gases was found to be 882.94 and 660.87 mg/g. • The DACTS exhibited a superior regeneration and repeatability performance towards VOCs. The diacid calix[4]arene tethered silica (DACTS) as an adsorbent was obtained by the tethering of calix[4]arene carboxylic acid derivative onto 3-glycidoxypropyl-bonded stationary phase (GBS). The characterizations were carried out by some analysis techniques such as FT-IR, XRD, EDS, SEM, and BET. The adsorption behavior of the prepared adsorbent was investigated towards the dynamic adsorption of volatile organic compounds (VOCs) such as xylene and toluene gases. For the optimization of process parameters, response surface methodology (RSM), and Box-Behnken design (BBD) were applied. The adsorption results were evaluated in terms of the kinetic and isothermal conditions. Hence, DACTS showed substantial adsorption performance towards xylene and toluene gases. It was observed that for xylene gas, the adsorption capacities of the precursor calixarene, GBS, and DACTS were 441.43, 542.98, and 882.94 mg/g, respectively. Additionally, their adsorption capacities towards toluene gas were found as 300.50, 398.14, and 660.87 mg/g, respectively. Hence, the tethering of calixarene units into GBS could considerably enhance the adsorption capacity of prepared adsorbent towards xylene and toluene gases. Additionally, as well as the excellent adsorption behavior towards xylene and toluene gases, DACTS adsorbent has a superior regeneration and repeatability performance towards VOCs. The possible adsorption mechanism can be explained by π-π and, van der Waals interactions between the VOCs and the benzene rings on calixarene moiety. The findings of this study indicated that the successfully synthetized DACTS adsorbent has excellent adsorption capacity and repeatability for VOCs, which means that it will be useful adsorbent for many areas. [ABSTRACT FROM AUTHOR]

• The silica gel supported dinitro calix[4]arene cage was successfully prepared, characterized, and used for methylene blue (MB) adsorption for the first time. • The applicability of DNCC for MB adsorption in real samples such as tap water and textile wastewater was investigated. • MB adsorption by DNCC was comprehensively evaluated in terms of thermodynamics, kinetic, and isotherm. • The MB uptake of DNCC was determined to be 212.770 mg g−1. The silica gel supported dinitro calix[4]arene cage (DNCC) was successfully prepared by immobilization of 3-glycidoxypropyl-bonded stationary phase (GBS) on p-tert- butylcalix[4]arene derivative having p -nitro benzyloxy moieties. The structural and composition analysis of the DNCC was performed by FT-IR, XRD, EDX, SEM, BET, and TGA techniques. After that, the proposed polymeric material as an adsorbent was used for the adsorption of methylene blue (MB) from aqueous solutions. Initial adsorption experiments demonstrated that DNCC showed outstanding performance for the removal of MB from aqueous solutions. Furthermore, many adsorption experiments were performed to evaluate the effects of some adsorption criteria on the MB adsorption. The MB adsorption capacity of DNCC was obtained approximately 212.770 mg g−1. Besides, thermodynamic parameters were evaluated and it was concluded that the MB adsorption came true in exothermically and spontaneously. Adsorption phenomena of MB on DNCC were clarified by the investigation of isotherm and kinetic criteria. Finally, the applicability of proposed adsorbent for MB adsorption was investigated in real samples such as tap water and textile wastewater. [ABSTRACT FROM AUTHOR]