Self-Assembled Melaminium Adipate Lamellae for Adsorptive Removal of Anionic Dyes from Wastewater

Abstract

The growth in industrialization worldwide has resulted in continual discharge of organic dyes that contaminate the aquatic ecosystem. Common adsorbents employed for dye removal are often expensive and non-biodegradable, causing a problem of secondary waste generation on their disposal. Thus, the design of biocompatible, economical adsorbents is of utmost importance. Bis­(melaminium)­adipate adipic acid solvate (BMA), an ionic organic material, was synthesized from commercially available melamine and adipic acid. Extensive hydrogen bonding stabilizes BMA sheets that are interlinked by lattice adipic acid molecules, resulting in the lamellar morphology. Though BMA is electrically neutral, positive zeta (ζ)-potential, due to the presence of melaminium moieties on the surface, aids in the adsorptive removal of anionic dyes from wastewater. BMA demonstrated a preference for the adsorption of anionic dyes irrespective of the solution pH, owing to the availability of multiple protonation–deprotonation sites. The Freundlich isotherm model proved to be suitable in describing the equilibrium adsorption of Congo red, owing to the surface heterogeneity in BMA. The adsorbed dye could be recovered and reused, as dye desorption ensued in methanol at room temperature. BMA is reusable for several adsorption–desorption cycles. Its biodegradability ensures that the spent adsorbent is not detrimental to the environment. Thus, the wastewater treatment with BMA generates minimal waste, underlining its viability in practical effluent management.

Adsorption of organic dyes on macroporous melamine sponge incorporating conducting polypyrrole nanotubes

“…Melamine‐based composites with poly(vinyl alcohol) and nickel(II) oxide were tested for the adsorption of an anionic azo dye, Congo red 40,41 . Melaminium adipate was proposed for adsorptive removal of Congo red, from wastewater 42 . These examples illustrate that dye adsorption on melamine sponge alone has to be kept in mind when analyzing the dye adsorption results.…”

Polycarbodiimide for Textile Dye Removal from Contaminated Water

“…Previous studies have shown that certain materials that carry intrinsic positive charges or materials that can be protonated under acidic conditions can remove anionic dyes only and not neutral and cationic dyes based on electrostatic interactions. 38 However, due to a similar chemical nature, different acid dyes can occur in a mixture. Selective removal of certain dyes from a mixture can aid in dye purification and greatly facilitate dye reuse.…”

“…Thus, it is crucial to evaluate the effects of salts/high ionic strength on the dye removal process. Furthermore, salts in the dye solution have been found to affect dye adsorption. ,, As reported in the literature, we also used sodium chloride as a model salt to increase the ionic strength of the solution to assess the effect of high salt concentration on dye uptake by the PCD polymer. An increasing concentration of salt (NaCl) solution was added to the dye–polymer solution under acidic conditions.…”

“…The ability to remove selective dyes from a dye mixture could expand the application for specific purposes. Previous studies have shown that certain materials that carry intrinsic positive charges or materials that can be protonated under acidic conditions can remove anionic dyes only and not neutral and cationic dyes based on electrostatic interactions . However, due to a similar chemical nature, different acid dyes can occur in a mixture.…”

Multifunctional Magnetic Porous Microspheres for Highly Efficient and Recyclable Water Disinfection and Dye Removal

“…11 Therefore, eco-friendly, byproduct-free, and costeffective disinfection techniques are imperative for water treatment. Besides, among the diverse dye removal methods such as adsorption, 12 membrane filtration, 13 photocatalytic degradation, 14 and biological treatment, 15 adsorption is an appealing approach due to its high efficiency, low cost, and portability. 16 Nevertheless, simultaneous disinfection of microbes and dye removal usually require multistep treatments, longer durations, and higher operational cost.…”