Methylene blue
(C16H18N3SCl, 1.43 nm 0.61 nm 0.40 nm) was chosen based on
its importance and wide applications in various field notably
analytical chemistry, biology (staining procedure) and aquaculture
(antifungal). Stock methylene blue (MB) solution, 1000 mg/L was
prepared by dissolving 1 g of methylene blue, (CH3)2NC6H2(SN)
C6H3(CH3)2Cl (MW ¼ 373.88 g/mol, HmbG Chemicals) in 1 L of
distilled water. The stock solution was then kept in a dark surrounding
at room temperature prior to use. To study the effect of
initial MB concentration and contact time on MB adsorption by
SPWB, 0.5 g of the prepared activated carbon was added into a
series of 250 mL Erlenmeyer flasks containing 50 mL solutions of
5e400 mg/L of MB solution prepared from serial dilution of the MB
stock solution (0.25e20 mL)