Thermal, Chemical and ultrasonic assisted synthesis of carbonized Biochar and its application for reducing Naproxen: Batch and Fixed bed study and subsequent optimization with response surface methodology (RSM) and artificial neural network (ANN)

An adsorbent was synthesized using a cheap and locally available raw material, rice straw which was treated thermally and then chemically to form an activated rice straw biochar (ARSB). The ARSB was used for removing Naproxen, a widely used pharmaceutical compound. ARSB was used for the removing of Naproxen using both a batch and column study. The batch study was further optimised with using optimizing tools like artificial neural network (ANN) and response surface methodology (RSM). The isotherm, kinetics and thermodynamics of the adsorption process was analysed using the data of the batch study. A detailed analysis of the characteristics of ARSB was done by different characterization methods in order to acquire an in depth knowledge of its structural and functional characteristics. The highest removal was observed as 89.78% from batch study and 97.54% from Optimization study at pH 4, dose of 2.8 g/L using RSM. The adsorption of Naproxen on the ARSB was deduced to be following the Tempkin Isotherm and Pseudo second order kinetics. In case of the column study the highest efficiency was exhibited by the bed height of 7.62 cm and adsorbate concentration of 10 mg/L. The column study data was best explained by the Thomas model of column kinetics. From the regeneration study, it was found that the ARSB was able to maintain its effectivity even after repeated cycles of reuse.