hexavalent chromium removal from aqueous solution using functionalized multi-walled carbon nanotube: optimization of parameters by response surface methodology

background chromium is one of the most commonly used heavy metals in industry. it is known as a pollutant that its discharge into the environment needs special care. objectives the current study aimed to evaluate the functionalized multi-walled carbon nanotubes (f-mwcnts) as a novel adsorbent of chromium in aqueous solutions. materials and methods the virgin mwcnt was protonated using sulfuric acid as a strong oxidant. the operating conditions such as initial chromium concentration, contact time, adsorbent dosage and ph were evaluated in the adsorption process. a systematic model for chromium adsorption was presented based on the experimental design. response surface method (rsm), as a mathematical technique, was used for modeling and optimizing considerable parameters. all experiments were performed according to the standard methods for the examination of water and wastewater results according to the statistical analysis, r2 (0.998), adjusted r2 (0.996), prediction r2 (0.906), coefficient of variation (1.38%), and the mean removal efficiency (54.76%) were calculated. conclusions the f-mwcnts can be applied as an adsorbent with excellent properties in the adsorption process. the efficiency of 61.75% was predicted by the model in the optimum conditions. in the experimental condition an adsorption percentage of 59.44% was obtained.