Modeling and optimization of Direct Red 16 adsorption from aqueous solutions using nanocomposite of MnFe2O4/MWCNTs: RSM-CCRD model

Abstract

Nanocomposite of manganese ferrite/multiwalled carbon nanotubes (MnFe2O4/MWCNTs) was synthesized in aqueous media by hydrothermal method and its application as an adsorbent for Direct Red 16 (DR16) removal was investigated. Four important process parameters i.e., initial dye concentration (30–110mg/L), temperature (25–45°C), adsorbent dosage (2–6mg) and contact time (10–210min) were modeled and optimized to obtain the best response of DR16 removal using a central composite rotatable design (CCRD) combined with response surface methodology (RSM). The modeling results indicated that the influence degree of the factors on the adsorption capacity of MnFe2O4/MWCNTs was in the order of linear effect of initial concentration>linear effect of adsorbent dosage>quadratic effect of adsorbent dosage>interaction effect between adsorbent dosage and initial concentration>interaction effect between temperature and initial concentration. Also, contact time and temperature had no significant effect on the adsorption capacity statistically. The optimum conditions were found to be initial concentration=89.95mg/L, adsorption dosage=3mg, temperature=30°C and contact time=158.56min. Three confirmatory experiments were performed to evaluate the accuracy of the optimization procedure and maximum adsorption capacity of 285.56mg/g was achieved under the optimized conditions.