The adsorption behavior of multiple contaminants like heavy metal ions and p-nitrophenol on organic-modified montmorillonite

Abstract

Stearyl trimethyl ammonium chloride (STAC) and ethylenediamine (En) were successfully implanted into montmorillonite (MMt) interlayer to fabricate the novel adsorbent STAC-En-MMt for the simultaneous adsorption of Cu²⁺, Zn²⁺, and p-nitrophenol (PNP). X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, elemental analyzer, zeta potential analyzer, inductively coupled plasma mass spectrometry, and UV–visible spectrophotometer were used to investigate the microstructure characteristics of STAC-En-MMt and their adsorption capacity of target contaminants. Four factors such as pH, the molar ratio between En and STAC (R_En/STAC), the adsorption time (A_Time), and the adsorption temperature (A_Temp) were selected to investigate the adsorption capacities of Cu²⁺, Zn²⁺, and PNP onto STAC-En-MMt in ternary solution. The results indicated that the total simultaneous adsorption of Cu²⁺, Zn²⁺, and PNP onto STAC-En-MMt adsorbent with R_En/STAC = 0.75 reached up to 260.27 mmol·kg⁻¹ under the condition of pH = 6, A_Temp = 40 °C, and A_Time = 60 min. After three regenerations, there was still a good performance in the adsorption of STAC-En-MMt. The Langmuir adsorption isotherm indicated that the adsorption of heavy metals and PNP onto adsorbents were single-layer surface adsorption. Nonlinear adsorption kinetics simulation indicated that chemical adsorption occupied a predominant position in Cu²⁺ and Zn²⁺ adsorption, while PNP adsorption depended on physical adsorption. Compared with Zn²⁺, Cu²⁺ had higher affinity for the adsorption sites on STAC-En-MMt. However, the pore blocking caused by the Cu²⁺ and Zn²⁺ adsorption had a remarkably adverse effect on PNP adsorption.

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