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This study investigated the removal of tetracycline from wastewater using solar photocatalysis in a parabolic trough reactor. The Eosin-Y sensitized photocatalyst was fabricated using a three-step procedure involving direct annealing of melamine to yield g-C3N4, which was thermally exfoliated, hydrothermal precipitation reaction between g-C3N4, zinc chloride and iron chloride and a final dye sensitization step of the resultant composite using the mixing-adsorption method. The degradation performance of the photocatalyst was GCN < ZF < 25%ZF/GCN < EY-25%ZF/GCN. Faster degradation kinetics were observed in experiments conducted in synthetic wastewater compared to real wastewater. This was attributed to the interference of aromatic groups, competing ions and water turbidity. The effect of coexisting ions such as (Cl-, NO3- and SO42-) was also assessed at 100, 300, and 500mg/l concentrations of NaCl, Na2SO4, and NaNO3, respectively in real wastewater. The low doses (100mg/l) of Cl- and NO3- had a promoting effect of 0.75% and 5.26%, respectively, on the degradation constant, while higher doses inhibited degradation. Total Organic Carbon (TOC) studies carried out at 100mg/l salt concentrations showed that co-ions of SO42- had the lowest TOC removal (37.02%) while Cl- ions had the highest. Similarly, the SO42- ions had the highest inhibition effect on tetracycline degradation, while Cl- ions had the lowest. These findings confirm that high concentrations of anions decrease the photocatalytic performance of photocatalysts in wastewater, hence the need for adequate pre-treatment before applying photocatalytic treatment of real wastewater.
