Carbonaceous Adsorbents Derived from Agricultural Sources for the Removal of Pramipexole Pharmaceutical Model Compound from Synthetic Aqueous Solutions

Efstathios V Liakos,George Z Kyzas,Dimitrios A Giannakoudakis,Kyriazis Rekos,Athanasios C Mitropoulos

doi:10.3390/pr9020253

Abstract

The aim of the present study was to synthesize various samples of activated carbon (AC) from different agricultural sources as precursors, like orange peels, tea stalks, and kiwi peels, as well as sucrose. The synthesis of AC was achieved with chemical activation using H3PO4 and KOH. The produced AC samples were tested as adsorbents for the removal of a pharmaceutical model compound, pramipexole dihydrochloride (PRM), from synthetic aqueous synthetic solutions. The produced-from-sucrose AC presented the higher yield of synthesis (~58%). The physicochemical features of the materials were analyzed by FTIR spectroscopy, N2 physisorption, and SEM imaging. More specifically, the AC sample derived from sucrose (SG-AC) had the highest specific surface area (1977 m2/g) with the total pores volume, mesopores volume, and external surface area being 1.382 cm3/g, 0.819 cm3/g, and 751 m2/g, respectively. The effect of the initial pH and PRM concentration were studied, while the equilibrium results (isotherms) were fitted to Langmuir and Freundlich models. The maximum adsorption capacities were found to be 213, 190, 155, and 115 mg/g for AC samples produced from sucrose, kiwi peels, orange peels, and tea stalks, respectively.

Highlights

The synthesis of activated carbon derived from sucrose, as a carbonaceous precursor, gave an excellent yield (~58%) with a mesoporous structure (~59.3%) at a very low impregnation ratio of the activation agent (H3 PO4 ) per SG (1.7:1)
According to nitrogen physisorption tests, the activated carbon derived from sucrose had the highest surface area
It is worth noting that the other synthetic protocols require a prolonged duration for the preparation of AC before pyrolysis and higher energy consumption, when compared with the synthesis of sucrose activated carbon

Summary

Introduction

Activated carbons (ACs) is a class of materials with excellent adsorption capability [1,2,3,4,5], high specific surface area [6,7,8,9], and total pore volumes [10,11,12,13], where according to its porous structure it can be separated depending on the diameters of pores in microporous (0–2 nm), mesoporous (2–50 nm), and macroporous structures (>50 nm), respectively [6].It is important to highlight the definition of activated carbon; it is a carbon-rich solid that is derived from biomass or other carbonaceous substances, using pyrolysis. A carbon material is “activated” by processes that greatly increase the surface area of the material, allowing it to capture (or “adsorb”) a larger quantity of molecules This high adsorption capability allows activated carbon to be effective at removing contaminants from water and air, which is why activated carbon is typically intended for remediation or purification projects. The key factor in the use of activated carbon in remediation/decontamination technologies is to use the most appropriate primary source so as to prepare the AC with the highest specific surface, suggesting the highest decontaminative ability. For this reason, various agricultural peels (biochars) were tested as adsorbents [14]

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Conclusion