The figure also showed that the profiles have almost the same trends in their removal for both catechol and p-benzoquinone. The removal has increased up to 1.33% and 3.62% for catechol and p-benzoquinone, respectively, for the first 15 min. However, as it was prolonged to 30 and 45 min, the catechol removal was gradually increased up to 1.37% and 1.76%, respectively. The completed reaction decreased at 1.52% removal when t = 60 min. Although p-benzoquinone has better removal than catechol but its removal fluctuated which was 3.44%, 3.49% and 3.26% for the reaction period of 30, 45 and 60 min, respectively. Besides, the high removal could possibly due to the chemical structure of p-benzoquinone which is easy to convert into other intermediates
