Thermodynamic and Kinetic Studies for Adsorption of Reactive Blue (RB-19) Dye Using Calix[4]arene-Based Adsorbent Ranjhan Junejo, † Shahabuddin Memon, † Fakhar N. Memon, ‡ Ayaz Ali Memon,* ,† Fatih Durmaz, § Asif Ali Bhatti, ∥ and Ashfaque Ali Bhatti † † National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro 76080, Pakistan ‡ Department of Chemistry, University of Karachi, Karachi 75270, Pakistan § Department of Chemistry, Selcuk University, Konya 42075, Turkey ∥ Department of Chemistry, Government College University Hyderabad, Hyderabad 71000, Pakistan ABSTRACT: A current study demonstrates the removal of Reactive Blue 19 (RB-19) from industrial wastewater by synthesizing p-piperdinocalix[4]arene-immobilized silica resin (PASR). The surface morphology and functional group analysis were performed with scanning electron microscopy and Fourier transform infrared spectroscopy. The dye removal efficiency of PASR was analyzed through adsorption studies. Different parameters were optimized such as the pH value of dye, amount of resin, concentration of dye, and effect of electrolyte on adsorption. The adsorption mechanism was analyzed with Langmuir, Freundlich, and Dubinin−Radushkevich (D−R) isotherms. It was found that experimental data follow the Freundlich isotherm, which suggests multilayer adsorption. The column adsorption study was also evaluated by breakthrough and Thomas models. The Thomas model rate constant k TH (cm 3 mg −1 min −1 ) and maximum solid phase concentration was found to be q o = 2.702 mg·g −1 . The thermodynamic study reveals that the adsorption process is exothermic and spontaneous in nature. The kinetic study suggests that the adsorption process follows the pseudo-second-order kinetic model. 1. INTRODUCTION Synthetic colorants such as azo dyes are used in industries worldwide. 1,2 It is reported that about 7 × 10 5 tons of dyes are produced each year and used in the textile, food, and ink production. 3,4 The textile industry is a major cause of water pollution because of the dye effluent. 5,6 About 1000 tons of the textile waste effluent has been discharged each year into fresh water, which contains a number of different unreacted azo dyes. 7,8 Reactive dyes are anionic dyes that can be easily dissolved in water and mainly used for dyeing of cotton rayon, silk, wool, nylon, etc. 9,10 The chemical structure of the dye molecule is biologically inactive, but degradation by micro- organisms makes it possible to cleave the azo (NN) group, which results in the formation of aromatic amines that are toxic as well as carcinogenic in nature. 11,12 Thus, they become harmful for the aquatic life and cause many environmental problems. 13 Conventionally, different techniques were used for the removal of azo dyes such as adsorption, photodegradation, membrane separation, electrolytic chemical treatment, catalytic processes, and ozone treatment. 14 The adsorption process has got much more attention for the treatment of dye- contaminated water due to easy application, low cost, higher efficiency, and reproducibility. 15−17 Therefore, different types of inexpensive, reproducible, and environmentally favorable adsorbents have been produced. In this regard, calixarene- functionalized adsorbents with different solid supports have been efficiently used for the removal of azo dyes. The structural frame of calixarene serves as the receptor for a number of ionic and neutral guest species due to its flexible shape. 18 The upper- or lower-rim calixarene molecule offers an appropriate place for introducing different functional groups that can bind with several toxic dyes, 19 such as 5,11,17,23- tetrakis(N-piperidinomethyl)-25,26,27,28-tetrahydroxycalix- [4]arene, 5,11,17,23-tetrakis(N′-methyl-N-piperazinomethyl)- 25,26,27,28-tetrahydroxycalix[4]arene, and 5,11,17,23-tetrakis- [(dimethylamino)methyl]-25,26,27,28-tetrahydroxy-calix[4]- arene, have been applied for the liquid−liquid extraction of sulfonated dyes such as red-2 (RR-2), acid black (AB), and (RB-19), respectively. 20 Keeping in view of the above performance of calixarene, in this study, we have synthesized the p-piperdinomethylcalix[4]arene and immobilized on the surface of silica to provide a solid support and increase its surface area for the maximum efficiency of dye removal with a regenerable property. Received: March 12, 2019 Accepted: June 12, 2019 Article pubs.acs.org/jced Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.jced.9b00223 J. Chem. Eng. Data XXXX, XXX, XXX−XXX Downloaded by UNIV OF TOLEDO at 23:08:15:187 on July 05, 2019 from https://pubs.acs.org/doi/10.1021/acs.jced.9b00223.