Search

Whitlockite has the advantages of a low sintering temperature, high stability, and a low fabrication cost, and it is widely used as the host for luminescent material. In this study, Ca1.8Li0.6La0.6−x(PO4)2:xDy3+ phosphor was prepared by the high-temperature solid-state method, and its structure, composition, and luminescence properties were systematically studied. The results showed that a new whitlockite type matrix was prepared by replacing Ca2+ in whitlockite with monovalent and trivalent cations. The prepared phosphors belonged to a hexagonal crystal system with a particle size in the range of 5–20 μm. Under the excitation of 350 nm UV light, the samples emitted white light, and there were mainly two stronger emission peaks at 481 nm in the blue band and 573 nm in the yellow band, which correspond to the electron transitions at 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. The optimal doping concentration of Dy3+ in Ca1.8Li0.6La0.6(PO4)2 matrix was 0.03 (mol%). The main mechanism of concentration quenching in the sample was dipole–dipole energy transfer. When the temperature was 130 °C, the luminescence intensity of the samples was 78.7% of that at 30 °C, and their thermal quenching activation energy was 0.25 eV. The CIE coordinates of the sample at 30 °C were (0.2750, 0.3006), and their luminescent colors do not change with temperature. All the results indicate that Ca1.8Li0.6La0.6−x(PO4)2:xDy3+ phosphor is a luminescent material with good luminescence performance and thermal stability, which shows a promising application in the field of LED display.

Arsenic (As) contamination of surface water has long been a threat to human health. Extensive studies were made at the bench-scale for the removal of As from water. Commonly-used materials for the removal of As include Al and Fe hydroxides that will form complexes with As. Recently, modification of Earth materials to reverse their surface charge to positive to reduce the mobility of arsenite and arsenate also attracted great attention. In 2008, a severe As contamination was reported in the lake of Yangzonghai, Yunnan, China. Although the As concentration was maintained below 0.05 mg/L for the lake, after 28 months of restoration, the discharge of mine tailings from a nearby fertilizer plants was still one of the contributors to the As in the lake. In this study, zeolite was modified by ionic liquids and the modified materials were installed as a permeable reactive wall (PRW) to contain the As movement. Preliminary results showed more than an 80% reduction in As after surface water moved through the PWR over the six-month sampling period confirming the effectiveness of ionic liquid-modified Earth materials for environmental application.