Elsevier

Microporous and Mesoporous Materials

Volume 185, 1 February 2014, Pages 121-129
Microporous and Mesoporous Materials

Adsorption characteristics of phenolic and amino organic compounds on nano-structured silicas functionalized with phenyl groups

https://doi.org/10.1016/j.micromeso.2013.10.017Get rights and content

Highlights

  • Ph-MSs with different compositions were synthesized via co-condensation.

  • Adsorption affinity of Ph-MS for BPA increased with surface hydrophobicity at low concentration.

  • Ph-MS exhibited good characteristics as a recyclable adsorbent.

  • The selective adsorption behavior of Ph-MS was investigated using several organic adsorbates.

  • Both hydrophilic and hydrophobic interactions were involved in the adsorption of Ph-MS.

Abstract

Phenyl-functionalized mesoporous silicas (Ph-MSs) were synthesized as adsorbents of bisphenol A (BPA) from aqueous solutions via co-condensation method. Ph-MSs with different compositions, which were prepared using 10%, 15%, 20%, and 30% of phenyltriethoxysilane (PhTES) in silica precursors, were used in the adsorption of BPA in order to investigate the effect of surface hydrophobicities on the uptake of hydrophobic organic compounds. Material characterizations were carried out including X-ray diffraction, N2 adsorption/desorption measurement, elemental analysis, Fourier transform infrared spectroscopy, and measurement of point of zero charge. The higher composition of PhTES offered higher hydrophobicity to the prepared Ph-MSs, whereas decreasing their structural order and surface area. Adsorption capacity of Ph-MSs for BPA depended on the surface area rather than the surface hydrophobicity. However, the adsorption data at low concentrations showed that the adsorption affinities for BPA were in the order of Ph-MS30 > Ph-MS20 > Ph-MS15 > Ph-MS10, which were fully consistent with the order of their surface hydrophobicities. Among the prepared materials, Ph-MS20 was selected as a representative adsorbent, and used to investigate further adsorption characteristics. Several aromatic compounds including p-t-butylaniline, p-t-butylphenol, aniline, and phenol, which had the similar molecular structures with BPA, were also adopted as adsorbates for the adsorption onto Ph-MS20. The selective adsorption behavior of Ph-MS was discussed using the equilibrium isotherms of the adsorbates on Ph-MS20.

Introduction

There have been growing concerns over the potential health threats by endocrine disrupting chemicals (EDCs) which may interfere with human hormones. The exposure to EDCs, which can occur through the contact with soil, water, or air contaminated with chemicals, is one of the most important topics in recent environmental studies [1], [2], [3]. Bisphenol A (BPA), one of EDCs, is an organic compound used to produce polycarbonate plastics and epoxy resins. These chemical products containing BPA are widely used as containers of food and drink, dental sealants, and baby bottles [4], [5], [6], [7], [8], [9]. Low concentrations of BPA have been identified in wastewater, river water, effluents after treatment of landfill leachate, and even in finished-water samples because BPA is not completely removed during the conventional water and wastewater treatment processes [10], [11], [12], [13]. This can lead to the presence of BPA in aquatic environment and drinking water.

It is necessary to reduce the amount of BPA in water, wastewater, and drinking water treatment plants to the levels less than the concentrations required to prevent adverse health effects. Among the several alternatives for the removal of EDCs, adsorption technology has been recognized as an effective and economic method [2], [14], [15]. Many researches on the BPA removal from aqueous solutions have been carried out using adsorbents such as mineral, carbon materials, and zeolites [16], [17], [18], [19]. However, most of adsorption processes does not seem to remove BPA selectively, and thus high concentrations of another organic pollutant can be primarily captured, saturating adsorption sites.

In recent years, mesoporous silicas, which have the possibility of modifying surface functional groups and the unique structural and surface chemistry, have been intensively studied for the adsorption of pollutants in water [20], [21], [22], [23], [24], [25], [26]. In particular, high adsorption selectivity for some EDCs was obtained via simple grafting hydrophobic functional groups onto the surface of mesoporous silica. The molecular form of organic pollutants as well as the functional groups on the surface of the mesoporous silicas was the key factor in the selective adsorption of EDCs on the mesoporous adsorbents [27], [28], [29], [30]. In the previous work [31], we reported that organic–inorganic hybrid mesoporous silicas incorporated with phenyl groups showed large adsorption capacity and higher adsorption selectivity for BPA against phenol than activated carbon (AC) from aqueous solutions. The high adsorption selectivity may be ascribed to the hydrophobic and hydrophilic surface groups of the hybrid adsorbents interacting with two benzene rings and two hydroxyl groups of BPA, respectively [31].

In this work, we prepared phenyl-functionalized mesoporous silicas (Ph-MSs) with different compositions and thus different surface hydrophobicities via co-condensation method. Adsorption characteristics of BPA from aqueous solutions were investigated using the prepared materials. In addition, the selective adsorption behavior of Ph-MS was discussed using the equilibrium adsorption isotherms of the organic compounds including phenol, aniline, p-t-butylphenol, and p-t-butylaniline, which had the similar molecular structures with BPA.

Section snippets

Reagents

Silica sources, tetraethoxysilane (TEOS, 99%) and phenyltriethoxysilane (PhTES, 99%), were obtained from Aldrich. Hexadecyltrimethylammonium bromide (CTAB, 99%, Sigma), sodium hydroxide (NaOH, 98%, Junsei), and ethanol (99.8%, Ducksan) were used to synthesize adsorbents. Bisphenol A (BPA, 99%, Aldrich), phenol (99%, Aldrich), p-t-butylphenol (99%, Aldrich), p-t-butylaniline (99%, Aldrich) and aniline (99.5%, Aldrich) were used as adsorbates. All reagents were used as received without further

Characterizations

XRD patterns of MCM-41 and template-extracted Ph-MSs, and unit cell parameter (ahex) and d100 spacing values of the prepared materials were shown in Fig. 1 and Table 1. XRD data of the prepared materials except Ph-MS30 exhibited a major intense (1 0 0) reflection and a few additional weak peaks, indicating good structural order of the synthesized mesoporous structures. Structural order of Ph-MSs decreased with the increase of molar ratio of initial phenyl moieties. Decrease of the peak

Conclusion

Phenyl-functionalized mesoporous silicas (Ph-MSs) with different molar densities of functional groups were successfully synthesized by co-condensation method, and used as adsorbents for BPA removal from aqueous solutions. Ph-MSs with relatively large initial phenyl moieties had higher adsorption affinities for BPA of low concentrations in aqueous solutions, while they had relatively low mesostructural order, small surface area, and small adsorption capacity for BPA. Among the prepared

Acknowledgments

This research was supported by a Grant (R-01-2007-000-20690-0) and Basic Science Research Program (2013R1A1A2009723) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology.

References (55)

  • J.-H. Kang et al.

    Toxicology

    (2006)
  • S.D. Kim et al.

    Water Res.

    (2007)
  • H.-S. Chang et al.

    J. Hazard. Mater.

    (2009)
  • H.H. Le et al.

    Toxicol. Lett.

    (2008)
  • M. Mariscal-Arcas et al.

    Food Chem. Toxicol.

    (2009)
  • S.-H. Nam et al.

    Chemosphere

    (2010)
  • C.A. Staples et al.

    Chemosphere

    (1998)
  • T. Yamamoto et al.

    Chemosphere

    (2001)
  • P.E. Stackelberg et al.

    Sci. Total Environ.

    (2007)
  • Y. Yoon et al.

    Sci. Total Environ.

    (2010)
  • L. Joseph et al.

    Desalination

    (2011)
  • W.-T. Tsai et al.

    J. Colloid Interface Sci.

    (2006)
  • W.-T. Tsai et al.

    J. Hazard. Mater.

    (2006)
  • G. Liu et al.

    J. Hazard. Mater.

    (2009)
  • B. Lee et al.

    Micropor. Mesopor. Mater.

    (2001)
  • H. Yoshitake et al.

    Micropor. Mesopor. Mater.

    (2005)
  • L. Wang et al.

    Colloid Surf. A

    (2006)
  • N. Baccile et al.

    Micropor. Mesopor. Mater.

    (2008)
  • K. Inumaru et al.

    Micropor. Mesopor. Mater.

    (2006)
  • Y.-H. Kim et al.

    Micropor. Mesopor. Mater.

    (2011)
  • X.S. Zhao et al.

    Micropor. Mesopor. Mater.

    (2000)
  • S. Mustafa et al.

    Colloid Surf. A

    (2002)
  • P. Chingombe et al.

    J. Colloid Interface Sci.

    (2006)
  • G. Crini et al.

    Sep. Purif. Technol.

    (2007)
  • I.A.W. Tan et al.

    J. Hazard. Mater.

    (2009)
  • D. Batabyal et al.

    Sep. Technol.

    (1995)
  • C.-H. Wu

    J. Hazard. Mater.

    (2007)
  • Cited by (28)

    • Synthesis of a novel bifunctional hybrid molecularly imprinted poly(methacrylic acid-phenyltrimetoxysilane) for highly effective adsorption of diuron from aqueous medium

      2022, Reactive and Functional Polymers
      Citation Excerpt :

      Based on these observations, it can be assumed that diuron adsorption on the hybrid polymers at pH 4.0 might takes place mostly by means of hydrogen bonding between the carboxylic group of MAA and it its very unlikely ascribed by electrostatic interaction. The diuron adsorption can also be performed by π-π stacking interactions between the benzene rings from diuron and the phenyltrimethoxysilane [65]. Under more accentuated acid medium (below 4.0) the electrostatic repulsion forces predominate, leading to lower adsorption, while for pH above 4.0 the surface of adsorbent acquires negative charge and the number of cationic species (DH+) decrease, resulting in lower adsorption.

    • Synthesis of hierarchically structured T-ZnO-rGO-PEI composite and their catalytic removal of colour and colourless phenolic compounds

      2021, Chemosphere
      Citation Excerpt :

      Among these process, adsorption and catalytic reduction are a convenient and most used techniques for the removal of phenolic compounds due to its comparatively low cost, easy operating flexibility and no harmful side products (Park et al., 2017; Gopal et al., 2020). To date, various adsorbents or catalyst have been used for the removal of phenolic compounds such as minerals, polymers, activated carbon, carbon nanotubes, zeolites, and metal oxides (Zhang et al., 2013; Kim et al., 2014; Wang et al., 2013). Recently, graphene based metal oxides has been widely used for the removal and conversion of phenolic compounds, due to their high chemical stability, specific surface area and fast charge transfer (Kwon et al., 2015; Wang et al., 2015).

    • Enhanced adsorption of steroid estrogens by one-pot synthesized phenyl-modified mesoporous silica: Dependence on phenyl-organosilane precursors and pH condition

      2019, Chemosphere
      Citation Excerpt :

      The peak at 956 cm−1 belongs to the stretching vibration of Si-OH bond, and they decreased intensely in 20%MePh-MCM-41 and 20%EtPh-MCM-41, compared with the MCM-41, indicating the successful introduction of organic groups. Additionally, both the 20%MePh-MCM-41 and 20%EtPh-MCM-41 had additional C-H plane vibrations of the aromatic ring at 691 and 738 cm−1, CC stretching vibrations of the aromatic rings at 1432 cm−1, and Si-C band at 1131 cm−1, showing the successful embedment of phenyl groups (Kim et al., 2014; Fan et al., 2017). The presence of peak at 2980 cm−1 in the 20%MePh-MCM-41 and 20%EtPh-MCM-41 suggested the alkyl groups were introduced to the materials, which may be attributed to the insufficient hydrolysis of the organosilane (trimethoxyphenylsilane or triethoxyphenylsilane).

    View all citing articles on Scopus
    View full text