Preparation of poly(acrylic acid) exfoliated clay composite by in-situ polymerisation for decolouration of methylene blue from wastewater

Abstract

ABSTRACT Acid treated locally available Bijoypur white clay was exfoliated with dodecyl amine to facilitate in-situ polymerisation of acrylic acid (AA) using N, N′‐methylenebisacrylamide (MBA) crosslinker and ammonium persulphate as the initiator for the preparation of a novel adsorbent. In order to obtain poly(acrylic acid)-graft-modified clay composite (PAA-g-MC), the growing PAA chain was ‘grafted onto’ the modified clay surface. The structural properties of the composite adsorbent were studied by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray fluorescence (XRF), and scanning electron microscope (SEM). Thermal properties of the composites were measured by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of different process parameters such as pH of dye solution, contact time, initial concentration of dye, and adsorbent amount on the removal efficiency of methylene blue (MB) from aqueous solution was evaluated by batch experiments. Characteristics data from XRD and XRF for raw clay and acid-treated clay showed that Bijoypur clay is rich in kaolinite, which contains a significant amount of quartz. However, treatment with HCl reduces 55% of quartz and increases the percentage of kaolinite that made it suitable for adsorbent used. Adsorption results showed that PAA-g-MC composite showed a maximum adsorption of 162.3 mg g−1 of 100 mg L−1 MB dye solution at pH 7.25 after 80 min of adsorption using 0.03 g L−1 of the adsorbent. Langmuir and Freundlich adsorption isotherms were studied and the equilibrium adsorption data were found to be well fitted with the Langmuir adsorption isotherm. The interaction between adsorbent and MB molecules was explained by chemisorption, as suggested by the pseudo-second-order kinetic model. Maximum monolayer adsorption of 168.4 mg g−1 was calculated from the Langmuir adsorption isotherm which is very close to the experimental value of 162.3 mg g−1.