###### Abstract  
Pharmaceutical pollutants in water pose a serious environmental challenge. This research compared the adsorption capacity of mandarin orange peels (MOP) and activated carbon mandarin orange peels (AC-MOP) to adsorb methylene blue (MB) and Ibuprofen (IBF) from an aqueous solution. This is the first study to report on the uptake of Ibuprofen using carbonized mandarin orange peels activated with hydrochloric acid. The biomaterials were characterized using FTIR and SEM. Batch experiments with operational parameters such as pH, contact time, concentration and temperature were investigated for the adsorption of MB and IBF. Isotherms, kinetic calculations and thermodynamic parameters were calculated for the adsorption of MB and IBF. A positive \(\Delta\)H\({}^{\circ}\) suggested the reaction was endothermic, and \(\Delta\)G\({}^{\circ}\) values showed that the sorption process was spontaneous. The isotherm models best fit the Langmuir model with maximum sorption capacities of 74.15 and 78.15 mg/g for MB and IBF, respectively. The adsorption rate for MB was fast and took place within the first 10 min, whilst the removal of IBF was observed at 40 min. The kinetic model evaluation showed that pseudo-second-order was a suitable fit for the mechanism. The re-usability data indicated that the recovery of MB was 70.13%, and IBF was 87.17%. The adsorption capacity of IBF with the carbon-based MOP was higher than that of MB. The results indicated that AC-MOP could be used as an adsorbent for MB and IBF from water. The major advantage of this method is its effectiveness in reducing the concentration of dyes and pharmaceutical pollutants using inexpensive adsorbents.  
carbon; methylene blue; Ibuprofen; mandarin; adsorption +
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of the mandarins produced are consumed as juice, and more than 50% are wasted after juice making [16]. The waste is dumped in the environment, creating serious environmental challenges [17].  
Several studies have used mandarin orange peels as an adsorbent for various pollutants. A mandarin fruit peel was used to remove Cr(VI) and Pb(II) ions from an aqueous solution via adsorption ([PERSON] and [PERSON] 2020) [18]. [PERSON] et al. (2006) [11] investigated the adsorption of Co(II), Ni(II) and Cu(II) using mandarin peels. The uptake of methylene blue was investigated by [PERSON] et al. (2018) [19] using activated carbon from mandarin peels. [PERSON] et al. (2021) [20] used mandarin orange peels as a biosorbent to remove methyl orange and fast green. Mandarin orange peels were also used to remove AB14 dyes in a study by [PERSON] et al. (2022) [21]. [PERSON] et al. (2022) [22] used raw mandarin orange peels for the adsorption of methylene blue. [PERSON] et al. (2023) [23] also used pristine mandarin orange peels for the adsorption of methylene blue. In another study, [PERSON] and [PERSON] (2020) [13] carbonized mandarin orange peels using H\({}_{2}\)SO\({}_{4}\) to adsorb methylene blue; a maximum capacity of 196 mg/g was obtained. [PERSON] et al. (2023) [24] used cocoa shells to adsorb Ibuprofen. The calculated Ibuprofen adsorption capacities ranged from 16.67 to 23.81 mg/g for raw biomass and 30.59 to 38.95 mg/g for glycine functionalized biomass. Few studies have used carbonized mandarin orange peels as a potential adsorbent for methylene blue, and there are no investigations for methylene blue adsorption using mandarin orange peels that are carbon-activated with hydrochloric acid.  
This study is the first to report on the uptake of Ibuprofen using carbon-based mandarin orange peels. This study evaluates the activated carbon from mandarin orange peels using a different acid. This study assesses the uptake of methylene blue (MB) and Ibuprofen (IBF) from an aqueous solution using mandarin orange peels (MOP). FTIR spectroscopy and SEM were used to characterize the activated carbon mandarin orange peels (AC-MOP). Operational parameters such as pH, contact time, concentration and temperature were investigated for the adsorption of MB and IBF in batch mode.