An-Najah Staff

In search for safe techniques to manage waste pharmaceutical compounds drained in water, solar-driven degradation of phenazopyridine (a model drug) was investigated in aqueous media using different ZnO-based catalyst systems. Naked ZnO, CdS-sensitized ZnO (ZnO/CdS) and activated carbon-supported ZnO (AC/ZnO) have been studied. Both naked ZnO and AC/ZnO were highly efficient in mineralizing phenazopyridine, reaching complete removal in ∼50 min, with AC/ZnO having the higher edge. The ZnO/CdS system showed lower efficiency, due to screening of light by CdS. Moreover, the tendency of CdS to leach out Cd²⁺ ions discouraged the use of CdS as sensitizer in this work. In both ZnO and AC/ZnO systems, the photo-degradation reaction was induced by the UV tail of the solar light. The visible region, with wavelength longer than 400 nm, failed to induce photo-degradation. The reaction was faster with higher catalyst loading, until a maximum efficiency was reached at a certain concentration. The rate of reaction increased with higher drug concentrations up to a certain limit. The effect of pH value was studied, and the catalysts showed highest efficiencies at pH close to 7. Stability of ZnO to degradation was studied. Both catalyst systems showed lowered efficiencies on recovery and reuse. The results suggest that complete mineralization of waste drugs, commonly dumped in sewage water, with direct solar light is a potentially feasible strategy using the AC/ZnO catalyst.

In search for safe techniques to manage waste pharmaceutical compounds drained in water, solar-driven degradation of phenazopyridine (a model drug) was investigated in aqueous media using different ZnO-based catalyst systems. Naked ZnO, CdS-sensitized ZnO (ZnO/CdS) and activated carbon-supported ZnO (AC/ZnO) have been studied. Both naked ZnO and AC/ZnO were highly efficient in mineralizing phenazopyridine, reaching complete removal in ∼50 min, with AC/ZnO having the higher edge. The ZnO/CdS system showed lower efficiency, due to screening of light by CdS. Moreover, the tendency of CdS to leach out Cd²⁺ ions discouraged the use of CdS as sensitizer in this work. In both ZnO and AC/ZnO systems, the photo-degradation reaction was induced by the UV tail of the solar light. The visible region, with wavelength longer than 400 nm, failed to induce photo-degradation. The reaction was faster with higher catalyst loading, until a maximum efficiency was reached at a certain concentration. The rate of reaction increased with higher drug concentrations up to a certain limit. The effect of pH value was studied, and the catalysts showed highest efficiencies at pH close to 7. Stability of ZnO to degradation was studied. Both catalyst systems showed lowered efficiencies on recovery and reuse. The results suggest that complete mineralization of waste drugs, commonly dumped in sewage water, with direct solar light is a potentially feasible strategy using the AC/ZnO catalyst.

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO₂, TiO₂/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd²⁺ ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO₂/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd²⁺. This indicates limited future applicability of CdS-sensitized TiO₂ photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO2, TiO2/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd2+ ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO2/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd2+. This indicates limited future applicability of CdS-sensitized TiO2 photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO₂, TiO₂/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd²⁺ ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO₂/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd²⁺. This indicates limited future applicability of CdS-sensitized TiO₂ photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO₂, TiO₂/CdS, 2, as photo-catalysts. Despite that, 2 showed two main drawbacks. Firstly, the system was difficult to recover by simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd²⁺ ions under photo-degradation reaction conditions. In an attempt to solve out such difficulties, 2 was supported onto sand surface. The sand/TiO₂/CdS system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd²⁺. This indicates limited future applicability of CdS-sensitized TiO₂ photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.

In search for safe techniques to manage waste pharmaceutical compounds drained in water, solar-driven degradation of phenazopyridine (a model drug) was investigated in aqueous media using different ZnO-based catalyst systems. Naked ZnO, CdS-sensitized ZnO (ZnO/CdS) and activated carbon-supported ZnO (AC/ZnO) have been studied. Both naked ZnO and AC/ZnO were highly efficient in mineralizing phenazopyridine, reaching complete removal in not, vert, similar50 min, with AC/ZnO having the higher edge. The ZnO/CdS system showed lower efficiency, due to screening of light by CdS. Moreover, the tendency of CdS to leach out Cd2+ ions discouraged the use of CdS as sensitizer in this work. In both ZnO and AC/ZnO systems, the photo-degradation reaction was induced by the UV tail of the solar light. The visible region, with wavelength longer than 400 nm, failed to induce photo-degradation. The reaction was faster with higher catalyst loading, until a maximum efficiency was reached at a certain concentration. The rate of reaction increased with higher drug concentrations up to a certain limit. The effect of pH value was studied, and the catalysts showed highest efficiencies at pH close to 7. Stability of ZnO to degradation was studied. Both catalyst systems showed lowered efficiencies on recovery and reuse. The results suggest that complete mineralization of waste drugs, commonly dumped in sewage water, with direct solar light is a potentially feasible strategy using the AC/ZnO catalyst.

 

Mineralization of phenazopyridine, 1, in water, under solar-simulator radiation was efficiently achieved using nanoparticle CdS-sensitized rutile TiO2 , TiO2 /CdS,  2,  as  photo-catalysts. Despite that, 2  showed two main drawbacks. Firstly, the system was difficult to recover by  simple filtration, and demanded centrifugation. Secondly, the sensitizer CdS showed relatively high tendency to leach out hazardous Cd2+ ions under photo-degradation reaction conditions. In  an attempt to solve out such difficulties, 2  was supported onto sand surface. The  sand/TiO2 /CdS  system, 3, was easier to recover but showed slightly lower catalytic activity compared to 2. On the other hand, the support failed to prevent leaching of Cd2+ . This  indicates limited future applicability of CdS-sensitized TiO2  photo-catalyst systems, in solar-based water purification strategies, unless leaching out tendency is completely prevented.