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Hydrothermal Processes for Biofuel and Bioenergy Production
Published in Veera Gnaneswar Gude, Green chemistry for Sustainable Biofuel Production, 2018
Water, the universal solvent, is a polar solvent at ambient condition, which is capable to dissolve salts, sugar, acids, and bases. Water at ambient temperature and pressure is a very weak solvent for the non-polar solutes like oil, grease, and hydrocarbons [30]. However, liquid water at higher temperatures than boiling point, i.e., subcritical and supercritical water has completely different properties than water at room temperature. Sub- and supercritical water are more reactive as they behave like mild acid and base at the same time [30]. The solvent properties of sub and supercritical water shifts from polar to nonpolar solvent. As a result, hot pressurized liquid water is capable of dissolving oils, grease, and hydrocarbons (see Figure 7.3). The main benefit for using water medium is with the release of pressure or decrease of temperature shifts the properties of water into benign (polar) again, which first, enhances the separation, second, eases of regeneration of water, third, collects and stores water, and fourth, is harmless for the environment at ambient condition. That’s why water is considered as green solvent and processes using water as solvent or reaction medium are green processes. 2H2O(l)↔H3O+(aq)+OH-(aq) $$ 2H_{2} O(l) \leftrightarrow H_{3} O^{ + } (aq) + OH^{ - } (aq) $$ Kw=[H3O+][OH-] $$ K_{w} = [H_{3} O^{ + } ][OH^{ - } ] $$ pKw=pH+pOH $$ pK_{w} = pH + pOH $$
Ultrasound and microwave-assisted recycling of spent mercuric chloride catalyst
Published in Environmental Technology, 2022
Chao Liu, Lu Wang, Jinhui Peng, Libo Zhang
Firstly, SMC was pretreated by ethanol under ultrasonic assistance to extract organic carbon deposition. Ethanol is regarded as the most common green solvent due to its easy availability with high purity and low levels of toxicity [28]. Therefore, absolute ethanol was applied in the pretreatment experiment. The experiment was carried out in a glass beaker covered with plastic wrap under electro-thermostatic water bath. The maximum power of ultrasonic device (DW-SD20-1500, Hangzhou Dowell Ultrasonic Technology Co., Ltd., Hangzhou, China) is 1500 W with frequency of 20 kHz. Ultrasonic probe tip was immersed 1 cm in the solution with moderate magnetic stirrer. Effects of some main influencing factors, ultrasonic power (400–800 W), ultrasonic time (0.5–4 h), liquid/solid (L/S) ratio of ethanol and SMC (3:1–15:1 mL/g), extraction temperature (25–70°C) were investigated in detail and optimized process parameters were achieved.
Graphene oxide-based ZnFe2O4 catalyst for efficient adsorption and degradation of methylene blue from water
Published in Journal of Dispersion Science and Technology, 2022
Imdadullah Qureshi, Shaheedullah Khan, Muhammad Shazad Shifa, Arshad Hussain Wazir
Herein, we report an effective and economical one pot in situ green synthesis of rGo-based zinc ferrite (GZF) and its application for the degradation of MB. Our strategy was to attach some ions of Fe2+ in substitution to Zn2+, which not only enhances the magnetic character but also ensures best separation and degradation of MB. However based on literature survey, it has been find out that bare ZnFe2O4 could not act as degrading agent because of rapid recombination of its electron-hole pair and aggregation.[26] Hybridization of these ions inside the carbon allotropic form will lock the electron and thus prevent the excited electron from recombination.[27] In order to overcome this problem, our group developed a strategy to anchor ZnFe2O4 onto the backbone of rGo. The composite will act as an efficient degrading agent and will cause to exfoliate wrinkle sheets of rGO and ultimately result in increased surface area as well as higher efficiency of degradation. One of the prominent features of the study is utilization of green solvent, that is, ethanol. The synthesized composite is unique in terms of its activity as both adsorbent and degrading agent at a wide range of pH.
Rhodiasolv PolarClean – a greener alternative in solid-phase peptide synthesis
Published in Green Chemistry Letters and Reviews, 2021
Ashish Kumar, Anamika Sharma, Beatriz G. de la Torre, Fernando Albericio
The industrial era focused on covering the needs of the population. In contrast, attention is now moving towards sustainability, in agreement with the 12 Principles of Green Chemistry (1) and the philosophy of the Circular Economy (2). In the chemistry arena, the use of solvents is probably the biggest challenge. The excessive use of solvents in chemical synthesis is ubiquitous and hence contributes immensely to industrial waste, accounting for 56% of the material used in the manufacturing of pharmaceutical agents (3). In this context, an ideal green solvent is non-toxic, biodegradable, recyclable, inexpensive, and non-volatile, and it is produced from renewable sources (4–7).