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

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 (REn/STAC), the adsorption time (ATime), and the adsorption temperature (ATemp) 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 REn/STAC = 0.75 reached up to 260.27 mmol·kg−1 under the condition of pH = 6, ATemp = 40 °C, and ATime = 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.