A novel clay/sludge-based magnetic ceramsite: Preparation and adsorption removal for aqueous Cu(II)

Printing and dyeing sludge (PADS) and magnetic clay (MC, clay loaded with Fe3O4) were utilized as raw materials to prepare a novel ceramsite for Cu(II) removal from wastewater. The optimal preparation conditions were calcination temperature = 600°C, magnetic attapulgite (MA) : magnetic bentonite (MB) = 3:1, PADS = 40%, and iron content = 20%. The ceramsite prepared under these conditions (i.e. A600-3-20) had the best removal capacity for aqueous Cu(II). N2 adsorption and desorption isotherm confirmed that A600-3-20 was a porous material, with an average pore size of 14.78 nm and a surface area of 49.943 m2/g. Fe3O4 particles were successfully loaded onto the surface of the ceramsite, with a magnetic saturation intensity of 26.83 emu/g. The removal rate of Cu(II) from 40 mg/L solution by A600-3-20 reached 90%-98% under the optimal adsorption conditions. Adsorption kinetics fitted the pseudo-second-order dynamic model. Adsorption isotherm followed the Langmuir isotherm model, with the maximum adsorption capacity (qm) was 2.40 mg/g. The adsorption mechanisms were mainly dominated by chemisorption, including ion exchange and surface complexation. The magnetic ceramsite had no heavy metal leaching risk and displayed an excellent reusability, indicating its potential as an environment-friendly and low-cost adsorbent for aqueous Cu(II) removal.