Comments on "High-efficiency removal of dyes from wastewater by fully recycling litchi peel biochar"

This paper provided further discussion on some identified mistakes and inconsistencies. Such problems included (1) the determination and discussion on the pH_PZC value of the biochar, (2) the excellent adsorption capacity of the biochar toward the dye contaminant, (3) the proposd adsorption mechanism (i.e., chemical adsorption) only based on the best fitting of the experimental data to the kinetic model (i.e., the pseudo-second-order or Elovich model), (4) the conception on the Freundlich model, and (5) the presentation of the adsorption mechanism involved in hydrogen bonding. Some other potential problems regarding the determination of adsorption capacity of an adsorbent towards an adsorbate (q_e; mg/g) were additionally discussed herein. It gives readers a gentle reminder that the initial concentration of adsorbate (also known as the blank sample; C_o) always plays a vital role in accurately calculating the q_e value. The C_o value from experiment (i.e., 254 mg/L or 245 mg/L) is often dissimilar to the C_o value from theory (i.e., 250 mg/L). The difference becomes enormously significant when the C_o value reaches very high concentration (i.e., 1000 mg/L) because an extremely high dilution factor is applied to determine the concentration of adsorbate in solution. The author hopes that the comments and contents in this paper will be particularly helpful for other researchers who are interested in the field of adsorption science and technology. Some highly-readable recent publications, which comprise the different types of paper as "comment", "discussion", "perspective", and "critical review", have also introduced in this paper. The expert reviewers and editors should give a great concern to such problems for further evaluations of submitted manuscripts in the field.