Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

Abstract

In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R2 = 0.9991 for MB and R2 = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R2 = 0.9970) and RO16 (R2 = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions.

Removal of Methylene Blue Dye from Aqueous Solutions by Pullulan Polysaccharide/Polyacrylamide/Activated Carbon Complex Hydrogel Adsorption

“…The pseudo-first-order model is usually used to explain the liquid adsorption process, and the pseudosecond-order model can be used to think that the reaction is controlled by chemical action rather than physical migration. 24 The formulas are as follows (6) where k (min −1 ) is the first-order adsorption rate constant (7) where v 0 (mg•g −1 •min −1 ) is the adsorption rate without the adsorbent (8) where K i and C i are, respectively, the diffusion rate constant (mg•g −1 •min −1/2 ) and particle thickness constant (mg•g −1 ).…”

“…Methylene blue (MB) is a cationic dye that has been extensively employed in people’s daily lives. If MB is excessively used and not effectively removed, human tissue necrosis, high blood pressure, quadriplegia, and other human diseases will be caused after MB reaches the human body through the food chain. , The removal of MB using a cheap adsorbent has been confirmed as an internationally recognized efficient and environment-friendly dye adsorption method, which is capable of minimizing the pollution of MB to the environment. − Accordingly, exploring cheap and efficient adsorbents becomes the focus of research.…”

Comparison of Kinetics of Adsorption of Permanganate on Co-Al-Layered Double Hydroxide and MoS2 Nanocompounds

“…As reported before, [65][66][67][68][69] Co-Al-LDH was used as an adsorbent or one of components of an adsorbent and kinetics and thermodynamics of these processes were studied by researchers. As observed in our earlier work, 1 the boundary of regions of adsorption isotherms of MnO -4 on Co-Al-LDH under different conditions were shown in Table S1.…”

Synergistic degradation of malachite green by water surface plasma combined with Fe2+/PMS

“…Due to the development of leather and textile industries in China, dye wastewater has received extensive attention in recent years because of its variety, complex composition, large emissions and difficulty in biodegradation [1]. From the perspective of functional groups, dyes can be divided into azo, indigo, anthraquinone, sulfur, nitro, etc [2]. The direct discharge of highly toxic dye wastewater will cause serious harm to water ecosystem and human health [3].…”