Adsorption of Acid Blue 25 on Agricultural Wastes: Efficiency, Kinetics, Mechanism, and Regeneration

Abstract

In this study, Acid Blue 25 (AB25), which is a negatively charged synthetic dye was removed from an aqueous solution by adsorption onto agricultural wastes, including banana (BP) and durian (DP) peels. The adsorption performances of AB25 were related to surface characteristics of the agricultural wastes, including their chemical functional groups, net surface charge, surface morphology, surface area, and pore volume. Parameters affecting the adsorption, including contact times, initial concentration, pH, and temperature were investigated. The results revealed that the adsorption of AB25 followed pseudo-second order kinetics, and that the adsorption process was controlled by a combination of intraparticle and film diffusion with a two-step mechanism. The equilibrium data could be simulated by the Langmuir isotherm model, suggesting that AB25 molecules are adsorbed on active sites with a uniform binding energy as a monolayer on the adsorbent surface. The adsorption process was spontaneous and exothermic, and the adsorption capacity decreased with the pH of the medium. The spent adsorbents were best regenerated by acid treatment (pH 2), and could be recycled for several adsorption-desorption processes. Under ambient conditions, the maximum adsorption capacities of AB25 on BP and DP were 70.0 and 89.7 mg g−1, respectively, which is much higher than on a large variety of reported adsorbents derived from other agricultural wastes.

Adsorption Behavior and Dynamic Interactions of Anionic Acid Blue 25 on Agricultural Waste

“…These vibrational bands most likely originate from the functional groups of cellulose, hemicellulose, pectin, and lignin contained in PP [ 18 , 32 , 33 ]. Before adsorption, AB25 has bands at ~1590 and 1575 cm −1 (C=O stretch on anthrone), 1532 cm −1 (aromatic C=C), 1500 cm −1 (aromatic C=C), 1415 cm −1 (S=O … Na stretch), 1280 cm −1 (C–N stretch on aromatic amine), 1230 cm −1 (C–N stretch), 1180, 1040, and 1020 cm −1 (SO 3 Na) [ 11 , 34 ].…”

“…In particular, the detrimental effects of the pollutants, such as heavy metals and synthetic dyes, on the entire ecosystem and human health have prompted the drive to develop effective approaches to remove the pollutants from wastewaters [ 1 , 2 ]. A variety of physical, chemical, and biological approaches, such as membrane filtration [ 3 ], flocculation [ 4 ], advanced oxidation [ 5 , 6 ], ozonation [ 7 ], adsorption [ 8 , 9 , 10 , 11 ], ion exchange [ 12 ], Fenton processes [ 13 ], and biodegradation [ 14 ] have been explored to remove heavy metal and dye effluents from wastewater. Among these promising methods to remove the pollutants, adsorption has attracted much attention because it is simple, cheap and practical to implement and can be handled even by a small-scale industry using non-toxic materials.…”

“…The cost of the adsorbents and their maximum adsorption capacity ( ) are two of the important criteria used to evaluate their potential for cost-effective wastewater remediation. Industrial waste, agricultural waste, and biomass are among the most promising alternative materials used as adsorbents [ 10 , 11 ]. This is due to their low cost, reduced environmental footprint, and their availability.…”

“…In addition, they can be chemically modified to optimize the surface concentration of specific functional groups, and they can be carbonized followed by thermal or chemical activation to form activated carbon, which is the most effective adsorbent. By adapting and modifying the adsorption process, a variety of agricultural wastes have been explored as adsorbents [ 11 , 15 , 16 , 17 , 18 ].…”

“…In recent years, adsorptive removal of AB25 from aqueous solution has been investigated by exploring different types of adsorbents such as polymer-clay nanocomposites [ 20 ], pectin [ 21 ], activated carbons [ 22 , 23 ], and agricultural wastes. These include banana peel and durian peel [ 11 ], sawdust [ 15 ], Shorea dasyphylla sawdust [ 24 ], oak sawdust [ 15 ], cempedak durian peel [ 25 ], rambutan seed [ 26 ], hazelnut shells [ 15 ], shrimp shells [ 27 ], peach seed [ 28 ], plant leaves [ 29 , 30 ], and soybean waste [ 31 ]. Many of the adsorbents have been demonstrated to successfully remove AB25 from water systems with high efficiency.…”