Sorption of basic dyes onto iron humate.

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment

Background:

• Basic dyes are common water pollutants.
• Effective and low-cost sorbents are needed for dye removal.
• Iron humate (IH) is a potential candidate for dye remediation.

Purpose of the Study:

• To evaluate iron humate (IH) as a low-cost sorbent for removing five basic dyes from aqueous solutions.
• To investigate the sorption mechanisms, including the influence of aqueous phase composition and anionic surfactants.
• To develop and validate a model for dye sorption in the presence of surfactants.

Main Methods:

• Sorption experiments using five basic dyes (Methylene Blue, Methyl Violet, Crystal Violet, Malachite Green, Rhodamine B).
• Analysis of sorption data using a multisite Langmuir isotherm model.
• Investigation of Methylene Blue sorption with varying pH, inorganic salt concentrations, and in the presence of sodium dodecyl sulfate (SDS).
• Development and validation of a sorption model for cationic dyes and anionic surfactants.

Main Results:

• Iron humate exhibited sorption capacities ranging from 0.01 to 0.09 mmol/g for the tested basic dyes.
• Sorption was minimally affected by pH and inorganic salts but dramatically enhanced by the presence of sodium dodecyl sulfate (SDS).
• A proposed model accurately described the sorption of cationic dyes in the presence of anionic surfactants, involving both polar and nonpolar active sites.
• Dye sorption was rapid, with most dye removed within hours, and exhibited very low leachability from the loaded sorbent.

Conclusions:

• Iron humate is a promising, low-cost sorbent for removing basic dyes from water.
• The presence of anionic surfactants significantly enhances dye sorption capacity through a dual-site mechanism.
• The sorbent demonstrates efficient and rapid dye removal with excellent stability against leaching.