Green Synthesis of Advanced Carbon Materials Used as Precursors for Adsorbents Applied in Wastewater Treatment.

Huge amounts of vegetable waste, mainly resulting from the food industry, need large areas for storage, as they could cause hazardous environmental impact, leading to soil and water pollution or to CO2 emissions during accidental incineration. This work was aimed at recycling certain lignocellulosic waste (walnut shells, kernels of peach, apricot, and olive) to design advanced carbon material precursors (ACMP) to be used for obtaining nano-powders with high applicative potential in pollution abatement. Both waste and ACMP were characterized using proximate and elemental analysis, and by optical microscopy. Complex characterization of raw materials by FTIR, TGA-DTG, and SEM analysis were carried out. The ACMP were synthetized at 600-700 °C by innovative microwave heating technology which offers the advantages of lower energy consumption using 3.3 kW equipment at laboratory level. The ACMP ash < 3% and increased carbon content of 87% enabled the development of an extended pore network depending on degassing conditions during heating. TEM analysis revealed a well-developed porous structure of the synthesized ACMP carbonaceous materials. Due to the presence of oxygen functional groups, ACMPs exhibit adsorption properties highlighted by an iodine index of max. 500 mg/g and surface area BET of 300 m2/g, which make them attractive for removal of environmental pollutants such as dyes having molecule sizes below 2 nm and ions with pore dimensions below 1 nm, widely used industrially and found in underground waters (NO3-) or waste waters (SO42-).

Simultaneous amorphous silica and phosphorus recovery from rice husk poultry litter ash.

The livestock sector is one of the most important sectors of the agricultural economy due to an increase in the demand for animal protein. This increase generates serious waste disposal concerns and has negative environmental consequences. Furthermore, the food production chain needs phosphorus (P), which is listed as a critical raw material due to its high demand and limited availability in Europe. Manure contains large amounts of P and other elements that may be recycled, in the frame of circular economy and "zero waste" principles, and reused as a by-product for fertilizer production and other applications. This paper focuses on the extraction and recovery of amorphous silica from rice husk poultry litter ash. Two different extraction procedures are proposed and compared, and the obtained silica is characterized. This work shows that amorphous silica can be recovered as an almost pure material rendering the residual ash free of P. It also addresses the possibility of more specific phosphorous extraction procedures via acid leaching.