Sustainable use of low-cost adsorbents prepared from waste fruit peels for the removal of selected reactive and basic dyes found in wastewaters

Abstract

Agricultural wastes are potential sustainable adsorbents since they are available in large quantities, are low-cost, and may require little or no treatment, in some cases. In this study, several fruit peels, such as banana, orange, and pomegranate, were collected from local markets and prepared by a simple and eco-friendly method and used as natural adsorbents for the removal of both anionic (Reactive Red 120 (RR120), Reactive Black 5 (RB5), Remazol Brilliant Blue R (RBBR)) and cationic Methylene Blue (MB) dyes found in wastewaters. Many industries, such as leather and textiles, can release huge amounts of synthetic dyes into the wastewater during dyeing processes. These are one of the most important pollutants of water pollution as they cause enormous damage to the water body and also affect the health of organisms due to their toxicity and carcinogenicity. The search for a sustainable and at the same time efficient material for the removal of a wide variety of dyes is the innovation of this work. These peels were prepared by washing, drying, grinding, and finally sieving, under natural sustainable conditions. Porosometry (BET analysis), FTIR, SEM/EDS, and XRD techniques were used to characterize the fruit peels before and after the adsorption process. Factors affecting the adsorption of dyes (adsorbent dosage, pH solution, initial concentration of dyes, contact time, and temperature) were investigated. According to the results, in terms of the effectiveness of fruit peels as (natural) adsorbent materials, for anionic dyes, 5.0–6.0 g/L of banana or orange dry peels was sufficient to remove near or even more than 90% anionic dyes at pH 2.0, and 4.0 g/L was sufficient to remove 98% of cationic MB dye at pH 9.0. Similar amount of pomegranate peels had lower efficiency for anionic dyes (50–70%), while cationic MB was still efficiently removed (98%) at pH 9.0. Moreover, the adsorption process in all cases was found to better fit to pseudo-second-order model, in comparison to pseudo-first-order model. According to isotherms, Freundlich model fitted better in some cases to the equilibrium data, while the Langmuir model in others. Finally, this study demonstrates the viability of reusing the banana, orange, and pomegranate peel adsorbents for eight, four, and five cycles, showing a gradual reduction of around 50% of their effectiveness. Graphical Abstract

Comparison of Modified Peels: Natural Peels or Peels-Based Activated Carbons for the Removal of Several Pollutants Found in Wastewaters

“…Pomegranate peels were efficient mainly for cationic dye. Finally, this study demonstrates the viability of reusing the banana, orange, and pomegranate peel adsorbents for eight, four, and five cycles, showing a gradual reduction of around 50% in their effectiveness [25].…”

“…Very recently, banana, orange, and pomegranate peels were applied as natural adsorbents for the removal of both anionic and cationic dyes from wastewater [25]. A descriptive and comparative report is made in this study, and the results show that these peels are very efficient materials for all the dye categories studied.…”

“…Thus, researchers have studied other sources of adsorbents, such as agricultural wastes, used as natural adsorbents [21], that offer an economical and sustainable solution for several pollutants found in wastewater [22]. Examples of these agricultural wastes are some shells [23], roots [24], fruit peels [25][26][27], etc. Particularly, banana peels in powder form were examined as adsorbents for removing MB dye and pesticides, such as glyphosate and atrazine [28], or chlorpyrifos by lemon peels [29], from water.…”

The Use of Various Types of Waste Paper for the Removal of Anionic and Cationic Dyes from Aqueous Solutions

“…In recent years, great hopes have been fostered in the application of waste materials from the agri-food industry as unconventional sorbents [ 12 ]. The largest group of sorption materials tested so far was lignocellulosic plant biomass [ 13 , 14 ], including stems [ 15 ] and leaves of crops [ 16 , 17 ], seed hulls [ 18 , 19 ], nut shells [ 20 , 21 ], as well as fruit [ 22 , 23 ] and vegetable peels [ 24 , 25 ]. Ample studies have also been carried out on the removal of dyes using waste from the wood industry, such as sawdust [ 26 , 27 ], bark [ 28 , 29 ], cones [ 30 , 31 ], or tree leaves [ 32 , 33 ].…”