Use of sodium alginate biopolymer as an extracting agent of methylene blue in the polymer‐enhanced ultrafiltration technique

Abstract

In this study, the removal of methylene blue (MB) cationic dye from an aqueous solution was investigated using the polymer-enhanced ultrafiltration (PEUF) technique with sodium alginate (SA) as an extracting soluble polymer, in combination with an ultrafiltration membrane of regenerated cellulose with a 10 kDa molar mass cut-off. SA was characterized via Fourier-transform infrared spectroscopy and thermogravimetric analysis. For ultrafiltration studies, the washing method was used to evaluate various experimental variables, such as the pH, SA dose and initial MB concentration, and adsorption isotherms to identify the optimal adsorption conditions. Finally, the regeneration of the SA polymer was evaluated in five consecutive cycles of adsorption-desorption of MB. In the obtained characterization results, the structural composition of SA and the characteristic thermal stability of the polymer were verified. The PEUF results demonstrated that a retention capacity of 98% of the MB was realized at pH 8.0 using 0.025 g of SA at an initial optimal MB concentration of 50 mg L −1 . It is possible to observe that the Freundlich model better explain the interaction between the dye and the polymer surface. According to the results is demonstrated the regeneration capacity of the polymer and its subsequent reuse.

A Sulfonated All-Aromatic Polyamide for Heavy Metal Capture: A Model Study with Pb(II)

“…The Langmuir and Freundlich adsorption models were employed to understand the mechanism by which PBDI and PSS adsorb Pb(II). While adsorption isotherms and isotherm models (e.g., Langmuir and Freundlich) are generally applied to solid adsorbents, they can also be utilized to investigate water-soluble polymers and their interactions with heavy metals. , The Langmuir model assumes that only one sorbate can bind to each adsorption site, all of which are energetically equivalent, to form a monolayer across a homogeneous sorbent surface. − The nonlinear form of the Langmuir equation is the following: q normale = q normalm k normalL C normale 1 + k normalL C normale where q m (mg/g) is the maximum adsorption capacity at equilibrium, k L (L/mg) is the Langmuir constant which denotes the exchange rate between the adsorption and desorption of sorbate, and C e (mg/L) is the concentration of Pb(II) in the liquid phase at equilibrium.…”

“…While adsorption isotherms and isotherm models (e.g., Langmuir and Freundlich) are generally applied to solid adsorbents, they can also be utilized to investigate water-soluble polymers and their interactions with heavy metals. 11,26 The Langmuir model assumes that only one sorbate can bind to each adsorption site, all of which are energetically equivalent, to form a monolayer across a homogeneous sorbent surface. 27−29 The nonlinear form of the Langmuir equation is the following:…”

“…Polyelectrolytes have long been used for heavy metal removal as coagulants and flocculants in combination with ultrafiltration techniques. − Functional groups such as sulfonic acids, or salts thereof, carboxylic acids, and amineswhich utilize electron-rich heteroatoms such as N, O, and Soffer a means to chelate and remove cationic species from solution. , Poly­(sodium 4-styrenesulfonate) (PSS) in particular is ubiquitous as a commercially available polyelectrolyte used in heavy metal removal. ,− For ion exchange and adsorption applications, cross-links ensure that PSS remains insoluble in aqueous environments. ,,, However, PSS without cross-links is water-soluble and can be used for heavy metal binding combined with ultrafiltration to facilitate efficient removal of metals. ,, …”