Efficient removal of oxytetracycline from aqueous solution by a novel magnetic clay-biochar composite using natural attapulgite and cauliflower leaves.

A novel magnetic attapulgite-biochar composite (MABC) derived from natural attapulgite, cauliflower leaves, and FeCl ₃ was successfully prepared as a low-cost adsorbent for oxytetracycline (OTC) removal from aqueous solution. Characterization experiments by different techniques suggested that attapulgite clay particles and Fe ₃ O ₄ nanoparticles were successfully covered on the MABC surface. Compared with the pristine biochar (CLB) and attapulgite-biochar composite (ABC), MABC had the largest surface area, well-developed pore structure, and more surface oxygen-containing functional groups which could interact with organic pollutant via hydrogen bonding, π-π electron coupling, complexation, and ion exchange. The maximum adsorption capacity of MABC by the Langmuir model was 33.31 mg/g, which was dramatically higher than that of CLB and ABC. The effects of solution initial pH had little difference on the adsorption of OTC because of the buffering effect. Adsorbent-regeneration studies of MABC exhibited good reusability and separation property. All the results indicated that MABC could be used as a potential adsorbent because of its easy preparation and separation, high efficiency, wide pH range application, and abundant and cheap raw materials in the global ecosystem. Graphical abstract.