Polyacrylic acid/CTAB-bentonite coated filter paper: Efficient and rapid removal of anionic and cationic dyes

Highlights: • A novel composite coating adsorbent PAA/CTAB-Bent-FP was synthesized facilely. • Rapid adsorption and separation simultaneously by single-step filtration were realized. • Both anionic ORII and cationic MB could be removed efficiently. • The PAA/30%CTAB-Bent-FP exhibited excellent adsorption cycles toward MB. Adsorption is proven to be a practical way for the treatment of dye wastewater. Bentonite and cellulose were frequently used as the adsorbents. In this study, cellulose-based filter paper (FP) acted as flexible and renewable substrate, polyacrylic acid (PAA) as a binder, cetyl trimethyl ammonium bromide modified bentonite (CTAB-Bent) with various CTAB amount coated on FP composite adsorbent (PAA/CTAB-Bent-FP) were fabricated. The composites were characterized by scanning electron microscopy, Fourier transform infrared spectra, X-ray diffraction, thermogravimetric analysis and nitrogen adsorption-desorption isotherm. The introduction of CTAB increased the interlayer spacing of the parent bentonite and the thermal stability of PAA/30%CTAB-Bent-FP (30 wt% of CTAB in amount of Bent) was higher than that of FP. The adsorption performance of PAA/30%CTAB-Bent-FP toward dyes was investigated. The results of adsorption studies showed that the anionic ORII and cationic MB both could be adsorbed onto PAA/30%CTAB-Bent-FP efficiently and rapidly by simple filtration. 80% ORII and 86% MB removal efficiencies within 150 s at moderate dye initial concentration (250 mg L⁻¹) were achieved by PAA/30%CTAB-Bent-FP. More importantly, the PAA/30%CTAB-Bent-FP realized rapid adsorption of dyes and simply separation simultaneously by conventional filtration operation. The results of the recycle of PAA/30%CTAB-Bent-FP showed that it could be reused easily and feasible for high dye concentration system. In addition, the possible adsorption mechanism was proposed. As a practical feature, it's worth noting that the PAA/CTAB-Bent-FP worked at a wide pH range and could be used either as a solid adsorbent or a membrane for continuous wastewater treatment.