TY - JOUR

T1 - Structural, electrokinetic and surface properties of activated palygorskite for environmental application

AU - Rusmin, Ruhaida

AU - Sarkar, Binoy

AU - Biswas, Bhabananda

AU - Churchman, Jock

AU - Liu, Yanju

AU - Naidu, Ravi

PY - 2016/12/1

Y1 - 2016/12/1

N2 - Unlike smectite, the surface characteristics of palygorskite remain underexplored for its potential application in environmental remediation. In this study, palygorskite from Western Australia was activated through thermal (300 °C for 4 h), acid (4 M HCl for 2 h at 70 °C) and acid-thermal (acid treatment followed by heating at 300 °C for 4 h) treatments, and the structural and physico-chemical characteristics were examined against the raw clay mineral. The influence of activation was systematically investigated using X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, N2 adsorption-desorption measurements and solid state 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy. The XRD patterns indicated preservation of the crystalline structure of palygorskite following all the treatments. These findings were supported by the Al (IV) and Al (VI) coordination peaks (chemical shift ~ 55 and 2.9 ppm, respectively) which were unaltered in the 27Al MAS NMR spectra of the samples. The acid-thermal activated palygorskite exhibited the highest specific surface area (152.7 m2 g− 1) and pore volume (0.2137 cm3 g− 1) which respectively were 3-fold and 69% greater than the raw palygorskite. The potentiometric titration analyses highlighted the possible role of Al derivatives towards development of the surface charge of the activated palygorskites. Electrokinetic studies described the stability of the activated products (zeta potential values ranging from - 5 mV to - 32 mV) at different electrolyte (NaNO3) concentrations. Combined acid-thermal activated palygorskite displayed a stronger specific adsorption of multivalent cations, and held a direct relevance to environmental remediation. Findings of this study will assist in the development of palygorskite-based adsorbents for heavy metal contaminants remediation.

AB - Unlike smectite, the surface characteristics of palygorskite remain underexplored for its potential application in environmental remediation. In this study, palygorskite from Western Australia was activated through thermal (300 °C for 4 h), acid (4 M HCl for 2 h at 70 °C) and acid-thermal (acid treatment followed by heating at 300 °C for 4 h) treatments, and the structural and physico-chemical characteristics were examined against the raw clay mineral. The influence of activation was systematically investigated using X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, N2 adsorption-desorption measurements and solid state 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy. The XRD patterns indicated preservation of the crystalline structure of palygorskite following all the treatments. These findings were supported by the Al (IV) and Al (VI) coordination peaks (chemical shift ~ 55 and 2.9 ppm, respectively) which were unaltered in the 27Al MAS NMR spectra of the samples. The acid-thermal activated palygorskite exhibited the highest specific surface area (152.7 m2 g− 1) and pore volume (0.2137 cm3 g− 1) which respectively were 3-fold and 69% greater than the raw palygorskite. The potentiometric titration analyses highlighted the possible role of Al derivatives towards development of the surface charge of the activated palygorskites. Electrokinetic studies described the stability of the activated products (zeta potential values ranging from - 5 mV to - 32 mV) at different electrolyte (NaNO3) concentrations. Combined acid-thermal activated palygorskite displayed a stronger specific adsorption of multivalent cations, and held a direct relevance to environmental remediation. Findings of this study will assist in the development of palygorskite-based adsorbents for heavy metal contaminants remediation.

KW - Acid activation

KW - Electrokinetic behavior

KW - Heavy metal adsorption

KW - Palygorskite

KW - Surface properties

KW - Thermal activation

U2 - 10.1016/j.clay.2016.07.012

DO - 10.1016/j.clay.2016.07.012

M3 - Journal article

AN - SCOPUS:84995743508

VL - 134

SP - 95

EP - 102

JO - Applied Clay Science

JF - Applied Clay Science

SN - 0169-1317

IS - 2

ER -