Microwave-assisted preparation of almond shell-based activated carbon for methylene blue adsorption

Abstract

This study reports the synthesis of a novel adsorbent, hereinafter named almond shell-based activated carbon (ASAC), from waste almond shells (AS) via exposure to microwave radiation and the use of ZnCl 2 as a chemical activator. Synthetic conditions were further elaborated using the response surface methodology to optimize the adsorption capacity of ASAC for methylene blue (MB) dye. The optimized ASAC preparation conditions were found to be as follows: a mass (ZnCl 2 /AS) ratio of 3:1 (w/w) and microwave heating time period of 15 min at 900 W. A maximum ASAC yield of 39.67% and a MB adsorption capacity of 314.20 mg/g were obtained. ASAC was also characterized by N 2 adsorption-desorption measurement, scanning electron microscopy (SEM), Fourier-transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), and point of zero charge measurement. Optimized ASAC had a Brunauer-Emmett-Teller surface area of 839.60 m 2 /g and a total volume of 0.406 cm 3 /g. FTIR and XPS analysis exhibited a decline in oxygen-containing groups of ASAC as compared with AS. The adsorption behavior of ASAC for MB was fitted well to the pseudo-second-order model and the Langmuir isotherm model. These findings support the ease of preparation and cost effectiveness that make ASAC promising for use in environmental remediation.

Characterization of Activated Carbons Prepared from Almond Shells and Their Hydrogen Storage Properties

“…Ramesh et al (2015) studied the hydrogen adsorption behavior of activated carbons derived from tamarind seeds and found that the hydrogen storage capacity of activated carbon with a 1785 m 2 /g surface area was 4.73 wt % at room temperature and 40 bar . Activated carbons were produced from almond shells by physical and chemical activation methods. − Izgi et al (2019) prepared activated carbon by microwave irradiation from almond shells and determined that the maximal surface area was 1128 m 2 /g; and Du et al (2016) studied the synthesis of a novel adsorbent from waste almond shells (AS) and found that the optimized activated carbon preparation conditions were to be as follows: a mass (ZnCl 2 /AS) ratio of 3:1 (w/w) and microwave heating time period of 15 min at 900 W . As can be seen from the above studies, there is no study on the production of activated carbon from almond shells by the microwave irradiation method to store hydrogen.…”

“…30 Activated carbons were produced from almond shells by physical and chemical activation methods. 31−33 Izgi et al (2019) prepared activated carbon by microwave irradiation from almond shells and determined that the maximal surface area was 1128 m 2 / g; 34 and Du et al (2016) studied the synthesis of a novel adsorbent from waste almond shells (AS) and found that the optimized activated carbon preparation conditions were to be as follows: a mass (ZnCl 2 /AS) ratio of 3:1 (w/w) and microwave heating time period of 15 min at 900 W. 35 As can be seen from the above studies, there is no study on the production of activated carbon from almond shells by the microwave irradiation method to store hydrogen. Furthermore, almond shells are an agricultural waste like biomasses used in the production of some other activated carbon.…”

Biomass‐Derived Carbon Materials for the Adsorption of Organic Pollutants

“…Due to its short duration, homogeneity, selective and fast process, energy saving and simple operation, microwave-assisted carbonization has drawn increasing attentions. [88,121] The main difference between microwave-assisted and conventional heating methods is the way to generate heat. The heating rate of conventional carbonization is relatively low, and the heat is transferred from the surface to the interior, so the adsorption capacity of active carbon obtained is not ideal.…”

Hydrothermal synthesis and microwave-assisted activation of starch-derived carbons as an effective adsorbent for naphthalene removal

“…40,41 The increase of negative charge on adsorbent surface enhances the electrostatic attraction of naphthalene, thus increasing the adsorption capacity of HMAC and HC to naphthalene. 42…”