Models to predict sunlight-induced photodegradation rates of contaminants in wastewater stabilisation ponds and clarifiers

Two kinetic models were established for conservative estimates of photodegradation rates of contaminants under sunlight irradiation,in particular for wastewater stabilisation ponds and clarifiers in conventional wastewater treatment plants.These two models were designated for(1)contaminants with high photolytic rates or high photolytic quantum yields,whose photodegradation is unlikely to be enhanced by aquatic photosensitisers;and(2)contaminants withstanding direct photolysis in sunlit waters but subjected to indirect photolysis.The effortlessly intelligible prediction procedure involves sampling and analysis of real water samples,simulated solar experiments in the laboratory,and transfer of the laboratory results to realise water treatment using the prediction models.Although similar models have been widely used for laboratory studies,this paper provides a preliminary example of translating laboratory results to the photochemical fate of contaminants in real waters.

Natural sunlight irradiated flower-like CuS synthesized from DMF solvothermal treatment

Three-dimensional CuS hierarchical crystals with high catalytic activity had been successfully fabricated using a facile solvothermal process, The CuS microparticles showed different flower-like morphology and good dispersion by optimizing reaction conditions. It was found that using N,N-dimethylformamide （DMF） as the solvent reagent in the proper temperature conditions was favorable for the growth of hierarchically structured CuS. The hexagonal flower-like CuS synthesized at 170℃ for 60 min displayed broad-spectrum photocatalytic properties under ultraviolet （UV） and visible irradiation. The as-prepared CuS crystals exhibited good performance to decolorize methylene blue （MB） solution under visible light irradiation. The total organic carbon （TOC） removal of rhodamine B （RhB） solution was nearly 60% after 5 h of the natural sunlight irradiation, and the property was stable after testing over four recycles, demonstrating a potential application in waster water treatment.

g-C3N4/Ag/GO Composite Photocatalyst with Efficient Photocatalytic Performance: Synthesis, Characterization, Kinetic Studies, Toxicity Assessment and Degradation Mechanism

The g-C3N4/Ag/GO(CNAG)photocatalysts were synthesized by a facile two-step reaction route.The as-prepared CNAG samples were characterized by X-ray diffraction(XRD),Fourier transform-infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),photoluminescence spectroscopy(PL)and ultraviolet-visible diffuse reflectance spectroscopy techniques(UV-vis DRS).The photocatalytic activity was obtained by degrading rhodamine B(RhB)under simulated sunlight and the results showed that photocatalytic activity of CNAG was much higher than that of pure g-C3N4 and g-C3N4/Ag.When the mass ratio of GO was 6%,the as-prepared CNAG-6%sample possessed the highest photocatalytic activity and the kinetic constant of RhB degradation was 0.077 min-1,which was almost 4.3 times higher than that of pure g-C3N4(0.018 min-1)and 2.5 times higher than that of the g-C3N4/Ag(0.031 min-1)composite,respectively.The toxicity of CNAG samples was assessed via seed germination experiment and no significant inhibitory effect was observed.The enhanced photocatalytic activity could be attributed to the synergistic effect of partial surface plasma resonance(SPR)effect of Ag,strong visible light absorption and the high separation efficiency of photon-generated carrier.The CNAG-6%sample exhibited excellent stability during the cycle experiment.Finally,a possible photocatalytic mechanism was proposed.