Optimization of operating parameters for photocatalytic degradation of tetracycline using In2S3 under natural solar radiation

• The optimum conditions predicted for removal tetracycline.
• The excellent correlation between the predicted and measured values.
• The degradation of tetracycline using In2S3 under natural solar radiation.
• A quadratic model established.

Batch tests were employed to estimate the optimal conditions for photocatalytic degradation of tetracycline using In2S3 under natural solar radiation by response surface methodology. Three key operating parameters, such as dosages of In2S3, initial concentration of tetracycline and an initial pH value, were selected, and their interrelationships were studied by the Box–Behnken design. The experimental data and ANOVA analysis showed that the coefficient of determination (R2) was 0.9998, which demonstrated that the model was significant. The optimum conditions were predicted to give a maximal removal efficiency of 100% at the In2S3 dosage of 2.5 g/L, an initial tetracycline concentration of 20 mg/L and pH of 7.0. The prediction was tested by triplicate experiments, where a removal efficiency of 100% was achieved under the chosen optimal conditions. This excellent correlation between the predicted and measured values provided confidence in the model.