Removal of Remazol Turquoise Blue-G and paracetamol from aqueous solutions using nano and micro sized modified chitosan

In this study, the adsorption of Remazol Turquoise Blue-G dye using cross-linked chitosan-glutaraldehyde and the adsorption of paracetamol using a chitosan-bentonite composite were investigated in a batch system as a function of pH, adsorbent concentration, temperature, and initial concentration parameters, and in a continuous system packed column reactor as a function of flow rate and initial concentration parameters. Additionally, the Response Surface Methodology (RSM) was applied to optimize the system. For the adsorption of Remazol Turquoise Blue-G with nano-sized cross-linked chitosan-glutaraldehyde in the batch system, experiments were conducted at 50°C, with a stirring speed of 150 rpm, an adsorbent concentration of 0.25 g/L, and a pH of 2. The maximum equilibrium capacity and removal efficiency were determined to be 670.52 mg/g at an initial dye concentration of 700 mg/L, and 98.81% at an initial dye concentration of 100 mg/L, respectively. For the adsorption of paracetamol using the chitosan-bentonite composite, the batch experiments were carried out at 50°C, with a stirring speed of 220 rpm, an adsorbent concentration of 1 g/L, and a pH of 7. The maximum equilibrium capacity and removal efficiency were found to be 60.48 mg/g at an initial paracetamol concentration of 90 mg/L, and 69.4% at an initial paracetamol concentration of 10 mg/L, respectively. The adsorption process was modelled by applying Langmuir and Freundlich equilibrium isotherms, internal and external diffusion mass transfer models, and pseudo-first and second-order kinetic equations. The thermodynamic of the adsorption system was investigated, and changes in Gibbs free energy, enthalpy, and entropy at different temperatures were calculated. Additionally, the optimization of the batch system adsorption was carried out using the Response Surface Methodology. In the continuous packed-bed column reactor system, experiments were conducted at a constant temperature of 25°C, and optimum removal efficiencies were achieved at a flow rate of 0.9 mL/min. The maximum equilibrium capacity and removal efficiency for the adsorption of Remazol Turquoise Blue-G onto cross-linked chitosan-glutaraldehyde at pH 2 were found to be 32.2 mg/g at a feed concentration of 500 mg/L, and 42.7% at a feed concentration of 100 mg/L, respectively. For the adsorption of paracetamol onto the chitosan-bentonite biocomposite at pH 7, the values were determined to be 9.3 mg/g at a feed concentration of 50 mg/L, and 39.4% at a feed concentration of 10 mg/L, respectively. The constants and coefficients for the Langmuir and Freundlich isotherms used in equilibrium modeling, as well as those for the Adams-Bohart, Thomas, and Yoon-Nelson models applied