Application of ZnO nanorods as an adsorbent material for the removal of As(III) from aqueous solution: kinetics, isotherms and thermodynamic studies

International Journal of Industrial Chemistry (2018) 9:17–25 https://doi.org/10.1007/s40090-018-0136-5 RESEARCH Application of ZnO nanorods as an adsorbent material for the removal of As(III) from aqueous solution: kinetics, isotherms and thermodynamic studies Gutha Yuvaraja1 · Cheera Prasad2 · Yarramuthi Vijaya3 · Munagapati Venkata Subbaiah4 Received: 21 October 2016 / Accepted: 12 January 2018 / Published online: 31 January 2018 © The Author(s) 2018. This article is an open access publication Abstract Removal of metals from wastewaters causes a big concern from the environmental point of view due to their extreme toxicity towards aquatic life and humans. Application of As(III) from aqueous solution by ZnO nanorods as adsorbent has been investigated in the present study. The synthesized nanorods were characterized by XRD, FT-IR spectroscopy, SEM, and thermogravimetric analysis. Optimum biosorption conditions were determined with respect to pH, adsorbent dose, contact time, and temperature. The experimental data were examined using the Lagergren’s first-order, pseudo-second-order and intraparticle diffusion kinetic models. The results revealed that the pseudo-second-order kinetic model provided the best description of the data. Langmuir and Freundlich isotherm models were applied to the equilibrium data. The maximum As(III) sorption capacity of ZnO nanorods was found to be 52.63 mg/g at pH 7, adsorbent dose 0.4 g, contact time 105 min, and temperature 323 K. The calculated thermodynamic parameters, ΔGo (between − 5.741, − 5.342 and − 4.538 kJ/mol at 303–323 K), ∆Ho (13.75 kJ/mol) and ∆So (0.0616 J/mol K) showed that the sorption of As(III) onto ZnO nanorods was feasible, spontaneous and exothermic, respectively. Keywords ZnO nanorods · As(III) · Kinetics · Isotherms · Thermodynamics Introduction Water pollution due to the release of various toxic chemicals and dyes from industrialization and urbanization is a global problem [1–31]. Arsenic occurs naturally in the earth’s crust, and much of its dispersion in the environment stems from mining and commercial uses. In industry, arsenic is a byproduct of the smelting process (separation of metal from rock) for many metal ores such as zinc, lead and cobalt. It * Gutha Yuvaraja 1 Tianjin University Chemical Engineering Research Center, Tianjin University, Tianjin 300072, China 2 Biopolymers and Thermo Physical Laboratories, Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh, India 3 Department of Chemistry, Vikrama Simhapuri University, Nellore 524‑003, Andhra Pradesh, India 4 Department of Environmental Science and Engineering, Ewha Womans University, 11‑1 Daehyun‑Dong, Seodaemun‑Gu, Seoul 120‑750, Korea cannot be destroyed once it has entered the environment, so that the amounts that we add can spread and cause health effects to humans and animals. The effects of arsenic exposure include discoloration of the skin, gangrene, intestinal problems, and carcinogenic effects include skin, lung, liver, kidney, and bladder cancers and ultimately death [32]. To reduce the health risks of human beings, the U.S. Environmental Protection Agency (USEPA) revised the maximum contaminant level (MCL) for arsenic in drinking water from 50 to 10 μg/L [33]. Arsenic occurs in the environment in several oxidation states such as − 3, 0, + 3 and + 5. Inorganic arsenic is generally found as trivalent arsenite or pentavalent arsenate form in the aqueous solution. As(III) is a hard acid and preferentially complexes with oxides and nitrogen. Whereas As(V) behaves like a soft acid, forming complexes with sulfides [34]. The speciation of arsenic in water is usually controlled by redox conditions, pH, biological activity, and adsorption reactions [35, 36]. As(III) is more toxic than As(V) and it is very difficult to remove from water. As a result of heightened guideline of arsenic toxicity and regulatory 13 Vol.:(0123456789) 18 International Journal of Industrial Chemistry (2018) 9:17–25 changes, prompting innovative research efforts towards efficient removing arsenic from contaminated water is of critical importance. Many technologies such as coagulation [37], ion exchange [38], membrane filtration [39, 40], and precipitation [41] have been employed for the removal of metal ions from aqueous solutions and effluents. However, these methods can prove to be too costly, impractical to apply over large scales, or unable to remove trace quantities of the metalloid. To overcome these drawbacks, adsorption is a good alternative to remove metal ions from aqueous environment. Different types of adsorbents [42–49] have been used for the removal of a variety of pollutants from water. Recently, the application of nanomaterials, nanoadsorbents has come forth as a fascinating area of interest for the removal of metallic and dye pollutants from water [50–53]. A variety of nanoparticles titanium dioxide suspensions [54], chitosan nanoparticles [55], zinc oxide nanoparticles [56], Nickel/nickel boride nanoparticles-coated resin [57], zirconium oxide nanoparticles [58], MnFeO4 and CoFe2O4 [59] have been used for the removal of metal ions from water. Nanoparticles are having high adsorption capacity due to its large surface area. In this connection, utilization of nanoparticles has greater attention in metal ion removal process. As per the literature survey, there are no studies on the adsorption of As(III) using ZnO nanorods. Therefore, in the present study, ZnO nanorods have been used for the removal of As(III) from aqueous solution. The goal of this work is to investigate the sorption capacity of ZnO nanorods as an adsorbent for the removal of As(III) from aqueous environment. The effects of varying parameters such as pH, dose, initial metal concentration, contact time and temperature on the adsorption process were examined. To clarify the sorption kinetics of As(III) by ZnO nanorods, Lagergren’s pseudo-first-order, pseudo-secondorder and intraparticle diffusion models were applied to the experimental data. The isotherms of adsorption have been studied and various isotherm models, such as Langmuir, and Freundlich models, have been tested. In addition, thermodynamic parameters including the change in free energy (ΔGo), enthalpy (∆Ho) and entropy (∆So) were calculated to evaluate the thermodynamic behavior of the biosorption process. Materials and methods Materials All the reagents were of analytical grade with a purity of 99% and used as received without further purification. ZnSO47H2O (S. D. Fine chemicals limited), KOH (Qualigens fine chemicals) tetraethyl orthosilicate (Sigma Aldrich). The glassware used was soaked in 10% H NO3 overnight 13 before use and cleaned repeatedly with double distilled water. The stock solutions of As(III) were prepared by dissolving As2O3 in double distilled water. Fresh dilutions were used for each study. The initial pH of each solution was adjusted with 0.1 M HCl and NaOH. Synt (...truncated)