Lidija Ćurković

The volume erosion rate of the slip cast monolithic and composite ceramics was studied using SiO 2 and SiC particles as erodents, under different impact angles (30°, 60°, 90°), at room temperature. Therefore, three groups of samples were prepared: (i) monolithic alumina (Al 2 O 3 ); (ii) composite alumina–zirconia (Al 2 O 3 –ZrO 2 ) containing 99 wt-% Al 2 O 3 and 1 wt-% ZrO 2 and (iii) composite alumina–zirconia (Al 2 O 3 –ZrO 2 ) containing 90 wt-% Al 2 O 3 and 10 wt-% ZrO 2 . Erosion mechanisms of all prepared ceramic samples were evaluated by the volume erosion rate ([Formula: see text], mm 3 ·g –1 ). Obtained results were compared with the analytical Wiederhorn and Evans equations. The mechanical properties (hardness and fracture toughness) of prepared ceramic samples were compared with their [Formula: see text] under the above-mentioned conditions. It was found that the erosion of monolithic and composite ceramics increased with the increase of the impact angle. Volume erosion rate was highest at an impact angle of 90° and amounts to 115 mm 3 ·g –1 with SiC, and 12 mm 3 ·g –1 with SiO 2 erodent particles for monolithic alumina ceramics, 77 mm 3 ·g –1 with SiC, and 8 mm 3 ·g –1 with SiO 2 erodent particles for ceramics with the addition of 1 wt-% of ZrO 2 , and 61 mm 3 ·g –1 with SiC, and 7 mm 3 ·g –1 with SiO 2 erodent particles for ceramics with the addition of 10 wt-% of ZrO 2 . Therefore, it can be concluded that the erosion resistance of monolithic Al 2 O 3 increases with the increasing amount of ZrO 2 in the composite Al 2 O 3 -ZrO 2 ceramics, thus erosion resistance can be improved with the addition of ZrO 2 .

The adsorption of the antibiotic ciprofloxacin (CIP) from water solution by natural zeolite–clinoptilolite (CLI), magnetic clinoptilolite (MAG-CLI), and graphene oxide coated magnetic clinoptilolite (GO-MAG-CLI) was investigated. The novel approach of an environmentally friendly and cost-effective microwave-assisted method was applied for the magnetic composite synthesis. Detailed characterization of the prepared composites was achieved. In order to investigate the effect of the initial CIP concentration, pH, temperature, contact time, and type of adsorbent on the adsorption efficiency of CIP, and to obtain the optimal conditions for CIP removal, the response surface methodology central composite factorial design (RSM-CCF) was applied. The results obtained by the RSM-CCF showed that among the studied adsorbents, GO-MAG-CLI had the highest adsorption capacity for CIP, achieved for the initial concentration of 48.47 mg dm−3 at a pH of 5 and 24.78 °C after 19.20 min of contact time. The adsorption kinetics studied for the initial CIP concentration range of 15–50 mg dm−3 followed Lagergren’s pseudo-second-order model, and the Langmuir isotherm was the most suitable one to describe the CIP adsorption onto GO-MAG-CLI.