Formic acid is extensively utilized in various chemical industries and applications. So, formic acid can be present in the wastewaters of these industries. It is widely produced in aqueous solutions by fermentation processes. And also, it forms as a by-product in the production of chemical processes. Thus, the removal of formic acid from waste streams and production medium is very significant topic. The objective of this study is to remove formic acid from its aqueous solutions by adsorption and to optimize the adsorption process. In this context, in this study, the optimal conditions for formic acid adsorption by multiwall carbon nanotube were investigated by using response surface methodology. Face-centered central composite design based on response surface methodology was applied to investigate the effects of the initial acid concentration (2-10%, w/w), amount of adsorbent (0.01-0.03 g) and temperature (25-45 degrees C) on the adsorption capacity (q(e), mg acid adsorbed/g adsorbent). The acquired experimental results were appraised by means of analysis of variance. A second-degree model equation for the adsorption capacity was obtained to explain adsorption characteristics of formic acid by multiwall carbon nanotube. The acquired model equation was well in agreement with the experimental results. The response surface plots were illustrated and they also supported the compatibility of the model equation. The design study also showed that MWCNT is an effective adsorbent for the removal of formic acid from aqueous solutions. (C) 2019 Elsevier B.V. All rights reserved.