This study aims to investigate the adsorption of methylene blue (MB) over particulate durian peel waste, which is chemically-activated with hydrogen peroxide. The equilibrium data is well-described by the Freundlich isotherm model, which outlines where the MB adsorption takes place predominantly on multilayers and heterogeneous surfaces of the biosorbent. The Freundlich adsorption constants, KF and n, are 11.06 L/g and 2.94, respectively. Thermodynamic data suggests that the MB adsorption occurs spontaneously and exothermically. The enthalpy and entropy for the MB adsorption are obtained as 10.26 kJ/mol and 0.058 kJ/mol K, respectively, in the temperature range of 303–323 K. Based on the stepwise desorption method, the adsorption of MB is dominated by physical interactions, particularly hydrogen bonding.
Solvent-free microwave extraction (SFME) is proposed as a method for "green" extraction of edible essential oils extensively used in the fragrance, flavour, and pharmaceutical industries and also in aromatherapy. It is a combination of microwave heating and dry distillation, performed at atmospheric pressure without adding any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. Basil (Ocimum basilicum L.) was extracted with SFME at atmospheric pressure and 373 K for 30 min. The extracted compounds were removed from the aqueous extract by simple decantation, identified by gas chromatographymass spectrometry (GC-MS). Hydrodistillation (HD) of basil was performed with 400 ml of water for 4.5 h for comparison of the results with those provided by the proposed method. SFME method offers important advantages over HD, viz. shorter extraction times (30 min vs. 4.5 h); better yields (0.13 % vs. 0.11 %); environmental impact (energy cost is appreciably higher for performing HD than that required for rapid SFME), cleaner features (as no residue generation and no water or solvent used); and provides a more valuable essential oil. SFME is a green technology and appears as a good alternative for the extraction of edible essential oils from aromatic plants used in aromatherapy and food industry.
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