Peroxymonosulfate improved photocatalytic degradation of atrazine by activated carbon/graphitic carbon nitride composite under visible light irradiation.

The photocatalytic degradation of atrazine by activated carbon/graphitic carbon nitride composites with peroxymonosulfate (PMS) was investigated under visible light irradiation. The photocatalysts were prepared at different activated carbon (AC) loaded percentages and characterized by XRD, FT-IR, BET surface area, SEM, UV-Vis absorbance, photocurrent response and EIS. Several parameters which might influence the degradation efficiency were studied including PMS concentration, solution pH, catalyst dosage, initial atrazine concentration as well as water matrix effect. The results indicated that incorporation of AC contributes effectively in suppressing the recombination of electron-holes pairs and enhancing the photocatalytic performance of graphitic carbon nitride. More significantly, the degradation efficiency of atrazine showed remarkable improvement with PMS addition under visible light irradiation. The reaction rate constant of the 10% AC/g-C3N4/Vis/PMS system (0.0376 min-1) was approximately 2.9 times higher than that of g-C3N4/Vis/PMS system (0.0128 min-1). Results from quenching tests revealed that both sulfate and hydroxyl radicals were involved in the degradation of atrazine, while the latter is the main contributor. This paper constitutes an insight for the metal-free catalyst activation of PMS by photocatalysis for environmental remediation.

Speciation of phosphorus in the sediments of Lake Bini (Ngaoundere-Cameroon).

In this study, spatial and seasonal variations of phosphorus fractions in Lake Bini sediments were evaluated using a sequential extraction method. The sampling of water and sediments (surface and coring) was carried out at seven sites around the lake during the dry season and the rainy season. The results showed that phosphorus is mainly in the inorganic form (L-P+Ca-P+Fe-P) in the sediments whatever the season may be. The rank order of phosphorus extracts obtained was Fe-P>Ca-P>OM-P>L-P>Res-P. The maximum values of phosphorus (sum of each fraction) were obtained in the rainy season at the sites D6 (298.12 +/- 12.37 microg P/g) and D4 (244.93 +/- 11.06 microg P/g) located beside water source 2 and farmland 2, respectively. The average values of the phosphorus content vary from 05.29 +/- 1.05 microg P/g to 102.58 +/- 4.62 microg P/g for the upper layer (0-5 cm depth); 04.67 +/- 0.66 microg P/g to 70.06 +/- 2.82 microg P/g for the medium layer (5-10 cm depth) and finally 04.63 +/- 0.98 microg P/g to 55.24 +/- 5.17 microg P/g for the deep layer (10-15 cm depth). The results of principal component analysis showed that processes which enhance Ca-P and Fe-P accumulation are probably related to the same factor and the origin of P depends on the source of pollution. The nature of the season plays a significant role in the geochemical composition of the sediments in phosphorus and on the eutrophication level of Lake Bini.