In order to convert biomass (carbohydrate) into carbon materials, two main routes can be used, namely a pyrolysis approach or a hydrothermal carbonization (HTC) [10–12, 19, 20]. The HTC process can provide carbon materials with low energy consumption (<350°C) and with limited environmental impacts due to the non-generation of CO2 during conversion reactions. The HTC process is usually performed in a sealed autoclave and in the presence of water [10–12]. In VDA chemical 1913, Bergius has done pioneer works on cellulose conversion to carbon materials. The process he developed was thus extended to various

carbon sources like carbohydrates such as glucose [10, 12, 21]. In a similar field, Antonietti et al. have performed pioneer works by elaborating Crenolanib cost a variety of carbon-based microstructures and nanostructures from hard or soft sources such as orange peels, oak leaves, pine cones, pine needles, and rice [10–12, 17, 22, 23]. In the present study, our aim was to produce ultralow-cost membranes by sustainable routes to answer environmental issues (water and air filtrations) affecting some emerging

and third countries, such as Lebanon. The strategy we developed is based on the valorization of natural products and food industry by-products. We develop a process based on the hydrothermal carbonization of Lebanese beer wastes to produce carbon-based nanoparticles (NPs). The obtained NPs were then used to produce carbon membranes of which performances in water filtration and gas separation will be presented and discussed. Methods Synthesis of carbon-based nanoparticles by hydrothermal carbonization Carbon nanoparticles were synthesized from beer wastes by a hydrothermal carbonization process. Beer wastes were obtained from Almaza Brewery (Heineken International, old Beirut, Lebanon), rated as the first brewery in Lebanon since 1933. The wastes were collected after the filtration process of beer mixture and are essentially composed of malt, water, and yeast.

After drying at 100°C for 14 h, the ensuing solid was ground in a ball miller for 4 h at 200 rpm. Citric acid (Sigma-Aldrich Co., Dorset, England, UK) was used as an activating agent in the carbonization reaction [16]. The reaction was carried out in a non-stirred, 300-mL capacity Teflon-lined stainless steel autoclave (Parr Instrument Company, Moline, Illinois, USA), in which the temperature is controlled by a thermocouple (Eurotherm regulator, Invensys Eurotherm, Ashburn, VI, USA). During heating and due to experimental setup limitation, the temperature cannot exceed 350°C and the pressure of 200 bar. In a typical experiment, 15 g of beer wastes was dispersed in 120 mL of pure water for 30 min, and then, 30 mg of citric acid was added as an activating agent for the carbonization reactions occurring during the HTC process.