Application of response surface methodology for methylene blue dye removal from aqueous solution using low cost adsorbent

Abstract

The adsorptive removal of Methylene Blue (MB) dye using a low cost adsorbent, prepared from Parthenium hysterophorus, has been investigated. Response Surface Methodology has been employed to model statistically and optimize the process variables for preparation of adsorbent, removal of MB and recovery of adsorbed dye using Design Expert software. During optimization of carbonizing condition, weight ratio of activating agent to parthenium (1.0–1.5), temperature (450–550 ◦C) and time of carbonization (1–2 h) have been considered as input parameters and decolorizing power (DP) of prepared sample is regarded as response. The carbonization at 550 ◦C for 1 h, with a weight ratio of activating agent to parthenium at 1.05:1 has been found to be optimum condition. The sample thus obtained is termed as Charred Parthenium (CP) and is used for further studies on dye removal. To get the optimum condition for removal of dye using CP, four input parameters viz., initial concentration of dye (25–50 mg/L), weight of CP (0.2–0.5 g), pH (5–9) and temperature (30–40 ◦C) have been varied according to the experimental design as prescribed by software considering percentage removal of dye as response. The removal with initial concentration of MB 25 mg/L, weight of CP 0.22 g at pH 7 and temperature 35 ◦C has been found to be optimum and 93.4% removal is achieved. Finally, the spent adsorbent, termed as Spent Charred Parthenium (SCP), obtained at the optimum condition of dye removal has been taken to assess the recovery of dye. Three parameters viz., amount of SCP (0.2–0.5 g), pH (5–9) and contact time (1–3 h) have been chosen as input parameters whereas percentage recovery has been considered as response. The results indicate that pH has a great influence on the recovery of dye.