Activated carbon (AC) was modified by the coprecipitation method to induce magnetic properties for the removal of isonicotinic acid (iNA). Magnetization was done by using salts of Fe2+ and Fe3+ as precursors. The induced magnetism in magnetic activated carbon (MAC) was confirmed by Fourier transform infrared and field-emission scanning electron microscopy–electron diffraction spectroscopy analyses. Also, the stability of both AC and MAC was tested by TGA. Batch adsorption experiments were performed using both AC and MAC to see the effects of adsorption time (0–180 min), adsorbent amount (12–40 g/L for AC and 4– 80 g/L for MAC), initial iNA concentration (1.23–6.16 g/L), and temperature (298–333 K) on the removal efficiency. Steady state was reached at 120 min by using both adsorbents. Equilibrium data was best fitted by Langmuir and Temkin isotherms for AC and MAC, respectively. The maximum adsorption capacities were noted to be 0.406 g/g of AC and 0.071 g/g of MAC. Pseudo-second-order model fitted the kinetic data for both adsorbents. The magnetic property in MAC ensured easy separation of adsorbent using magnet after adsorption from the aqueous medium.

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Activated carbon (AC) is the most commonly used adsorbent for water purification, although the dispersive nature of AC in aqueous solution poses a serious problem. To overcome this limitation, AC was magnetized with iron oxide using iron salts as precursor. Further to enhance its effectiveness, it was impregnated with Aliquat 336. Different characterization techniques (Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), along with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD)) were used to analyze the adsorbent. Furthermore, the value of the pH at which the overall charge on the surface of the adsorbent is neutral was found by pH drift method. The modified form of the activated carbon was used to treat the aqueous solution of bisphenol-A in the batch as well as in the continuous mode of operation. In batch mode, the data were validated using equilibrium and kinetic models, and in continuous mode, data were fitted with the Thomas, Adams-Bohart, and bed depth service time (BDST) fixed bed adsorption models. Also, the changes in Gibb's free energy, enthalpy, and entropy were estimated from the temperature study. The design of an adsorption column is proposed to treat 10,000 L/day of an industrial effluent containing BPA.

A new type of adsorbent was developed by incorporating magnetic properties using the coprecipitation method and amine functionality by the wet impregnation method. The adsorbent was characterized using Fourier transform infrared spectroscopy and field emission scanning electron microscopy along with energy-dispersive spectrometry, X-ray diffraction, and by point of zero charge analysis. The modified adsorbent was used for removal of bisphenol-A from its aqueous solution in the batch and in the continuous mode of operation. The regeneration of the adsorbent was carried out to account for the reusability of the adsorbent. Different kinetic and isotherm models were used to validate the data obtained in batch and continuous column operations.

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