Elsevier

Environmental Research

Volume 201, October 2021, 111588
Environmental Research

Green sporopollenin supported cyanocalixarene based magnetic adsorbent for pesticides removal from water: Kinetic and equilibrium studies

https://doi.org/10.1016/j.envres.2021.111588Get rights and content

Highlights

  • Synthesis and characterizations of new green and honey-comb like cyno-substituted calix-based magnetic sporopollenin.

  • Removal behavior investigations of the new magnetic adsorbent for pesticides.

  • Optimization of parameters to evaluate removal performance of the MSP-CyCalix.

  • Pesticides adsorption on nanocomposite was fitted by Langmuir model.

Abstract

In this study, magnetic sporopollenin supported cyanocalixarene (MSP-CyCalix) nanocomposite was synthesized and introduced as an adsorbent material for the removal of pesticides from aqueous media. MSP-CyCalix was characterized by different analytical techniques FTIR, SEM, EDX, BET, VSMand TEM. Chlorpyrifos and hexaconazole pesticides were chosen as model analytes solutions for testing the adsorption efficiency of MSP-CyCalix adsorbent. The adsorption results showed that the incorporated cyano functional groups significantly increased the chemical reactivity and adsorption capacity for pesticides. To obtain the highest possible performance, experimental parameters such as pH, salt, dosage and time were optimized. Adsorption kinetics and isotherms models showed that pesticide adsorption process was well fitted with the pseudo-second-order and Langmuir models with a maximum adsorption capacity of 13.88 mg g−1 and 12.34 mg g−1 and a removal efficiency of >90% for both pesticides. Lastly, MSP-CyCalix maintained a removal efficiency of >80% for ten cycles and 60% after the eleventh cycles of usage. The results proved that MSP-CyCalix nanocomposite can be used as an efficient adsorbent for the removal of pesticide residues from water.

Introduction

Saving water from pollution is one of the greatest challenges of the 21st century. Among the common pollutants, organic contaminants are very stable and non-biodegradable can be highly toxic and carcinogenic for the environment (Jayaraman et al., 2018; Nejadshafiee and Islami, 2020; Theerthagiri et al., 2021). Pesticides a large group of organic contaminants are chemical substances that are commonly applied to fruit and vegetable crops in an agricultural environment (Zhigang et al., 2020). Due to their water-soluble nature, pesticides can be easily transferred into the environment through runoff from manufacturers and plants during washing and operation, which causes water pollution (Tang et al., 2020). Overall, pesticides have residues in soil, water, and other agricultural products. Generally, pesticides can impose great risks for mammal's lives and cause several neurotoxic diseases in humans due to their serious toxicity, mutagenicity and carcinogenicity (Shakourian et al., 2020). The maximum permitted concentration of few pesticides that are set by the World Health Organization (WHO) is 0.1–10 μg/L in drinking water. Therefore, the removal of pesticides from aqueous media is of particular significance.

For removing pesticides from water, different methods such as electrochemical oxidation, Fenton oxidation, UV photolysis, sonoelectrochemical, photocatalytic degradation and oxidation by ozone and adsorption have been suggested (Khoshnood and Azizian, 2012; Tang et al., 2020; Theerthagiri et al., 2020). Excluding adsorption, these methods have some disadvantages such as high cost and production of large amounts of chemicals (Zhigang et al., 2020). The nanoparticles are good for water treatment because they are high dissoluble in water as compared bulk material (Theerthagiri et al., 2019). Currently, magnetic Fe3O4 nanoparticles (NPs) have been extensively used for the removal of a wide variety of pollutants. These NPs are non-toxic, insoluble and stable in water, can be easily synthesized, and most interestingly can be easily recovered and isolated from water and wastewater (Ramu et al., 2020). Fe3O4 NPs have a large specific surface area and can be simply and rapidly regenerated by using an external magnetic field (Aydin, 2016; Li et al., 2020). Recently, renowned synthetic macromolecular compounds namely calixarene gained remarkable attention due to their chemical reactivity and the presence of phenolic hydroxyl groups, which can mediate and facilitate functionalization and immobilization with a vast range of choices (Ghaffarzadeh and Pur, 2020). Meanwhile, Sporopollenin is a highly cross-linked organic biopolymer that displays magnificent chemical, biological and physical stability (Sereshti et al., 2020). It presents a hollow structure with micrometer thick walls-perforated with numerous channels and pores thus very promising for adsorption due to the abundant available active sites on so that both inner and outer surfaces. Additionally, these abundant available large internal hexagonal cavities and walls facilitate the magnetization process of sporopollenin. It was proven in literature that the incorporation of the calixarene moiety onto magnetic sporopollenin can enhance the sorption capacity over pesticides and produce a robust adsorbent system (Kamboh et al., 2016). Lastly cyano (-Ctriple bondN) substituted systems have shown great efficiency and tendency towards pesticides adsorption (Gaweł et al., 2019; Rashidi Nodeh et al., 2016; Soutoudehnia Korrani et al., 2016). Magnetic calixarene doped graphene successfully used for pesticide removal, but the sorption capacity and functionality are the main challenges (Kamboh et al., 2016; Nodeh et al., 2019).

The objective of this study was to characterize MSP-CyCalix for the removal of pesticides. The cyano group was grafted into the adsorbent system to enhance the adsorption capacity. Effects of solution pH, salt concentration, adsorbent dosage, contact time, and analyte initial concentration on the performance of MSP-CyCalix were investigated. In addition, the equilibrium and kinetic properties of the adsorption process were studied to understand the adsorption mechanism and determine the efficiency of the adsorption of pesticides onto the surface of MSP-CyCalix adsorbent.

Section snippets

Chemicals

Tetraethyl orthosilicate (TEOS), epoxypropoxy-propyl-trimethoxysilane (EPPTMS), Sporopollenine (SP), FeCl2.4H2O, FeCl3.6H2O, ammonia solution (25%), ethanol and acetonitrile were purchase from Merck Chemicals (Darmstadt, Germany).

Instruments

FT-IR spectra (4000–400 cm−1) were recorded by PerkinElmer TM 400 FTIR Spectrometer (Waltham, MA USA) using KBr pellets. The FESEM images were obtained using Carl Zeiss Model Supra 35-VP FESEM (Oberkochen, Germany) which showed the size, morphology and structure of the

FTIR spectroscopy, BET and VSM analysis

FTIR study provides plenty of information about the present surface functional groups. Herein the FTIR spectrum (Fig. 2A) of the synthesized MSP-CyCalix (c) nanocomposite was compared with those of pure sporopollenin (a) and cyanocalixarene (b). The FTIR spectrum of sporopollenin (a) displayed all the characteristic bands occurring at 3400 cm−1, 2925-2850 cm−1, 1705 cm−1 and 1450 cm−1 that correspond to the stretching vibrations of hydroxyl (O–H), saturated carbons (C–H), and carbonyl (Cdouble bondO)

Conclusion

In the present study, MSP-CyCalix nanocomposite was successfully synthesized and characterized to remove both chlorpyrifos and hexaconazole pesticides from aqueous solution. The effect of experimental variables such as contact time, pH, salt addition, adsorbent dosage, contact time, and initial concentration of pesticide on the removal performance of MSP-CyCalix was investigated. Optimization results showed that the contact time of 10 min, pH 6, and adsorbent dosage of 5 mg achieved the

Credit author statement

Muhammad Afzal Kamboh: Writing – original draft, Methodology; Sadaf Sadia Arian: Conceptualization; Visualization; Ashique Hussain Jatoi: Resources; Software; Bibi Sherino: Writing – review & editing; Tahani Saad Algarni: Validation; Wedad A. Al-onazi: Writing – review & editing; Amal M. Al-Mohaimeed: Formal analysis; Shahabaldin Rezania: Writing – review & editing, Supervision

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors extend their appreciation to the Researchers supporting project number (RSP-2021/247) King Saud University, Riyadh, Saudi Arabia.

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