Co-hydrothermal treatment of fallen leaves with iron sludge to prepare magnetic iron product and solid fuel

Coevolution of Iron, Phosphorus, and Sulfur Speciation during Anaerobic Digestion with Hydrothermal Pretreatment of Sewage Sludge

“…During HT, hydrolysis of cellulose produces glucose, which is further hydrolyzed to produce furfural derivatives such as 5-hydroxymethylfurfural (5-HMF). These intermediates (i.e., 5-HMF) can reduce Fe­(III) to Fe­(II) under hydrothermal conditions. , During HT of sewage sludge, reduction of FeOOH in the absence of oxyanions forms magnetite, , whereas oxyanions (e.g., phosphate and carbonate) can complex with the produced Fe­(II) and form secondary mineral precipitates such as vivianite and siderite . The presence of phosphate inhibits formation of magnetite and green rust but can lead to preferential formation of the stable phase vivianite .…”

“…Meanwhile, the speciation of redox-sensitive elements such as iron (Fe) and sulfur (S) can also exert important controls on the chemical environment and mineral states of nutrients and metals. For example, HT treatment of biosolids was shown to convert organic phosphate into inorganic orthophosphate in the produced hydrochars. , The final P speciation is closely related to the composition/speciation of metals and their affinities for P, HT temperature and duration, the source of biosolids, and pH. ,, S in sewage sludge can react with metals to form metal sulfides via hydrothermal sulfidation. − HT of sewage sludge under acidic and neutral environments also creates reducing chemical environments, where organic matter can reduce Fe­(III) to Fe­(II) species, − such as the conversion of Fe 2 O 3 to magnetite …”

Transformation Kinetics of Phosphorus and Nitrogen in Iron-Rich Sewage Sludges during Hydrothermal Treatment and Recovery of Nutrients from Process Water

“…These observations are consistent with our recent study. 18 Formation of vivianite was due to the reduction of Fe(III) species by furfural derivatives such as 5-hydroxymethylfurfural (5-HMF), 57,58 which are intermediates during the decomposition of cellulose in sewage sludge by HT. However, 5-HMF is unstable at high HT temperatures and can convert into polyaromatic hydrocarbon type compounds by a series of reactions such as polymerization, polycondensation, and aromatization.…”

Preparation and characterization of nano silver immobilized hydrochar derived from hydrothermal carbonization of tobacco stem

“…The fuel property of TS was also expected to be enhanced after the HTC treatment. Moreover, the abundant functional groups of hydrochar, intermediate products of reactions and the soluble constituents of TS were reported to have some metal ions chelation and reduction capacity, which could reduce Ag + into Ag 0 and lead to the formation of AgNPs in situ during the HTC process [21,22]. Table 2 shows the proximate analysis of raw TS and the AgNPs immobilized hydrochar smaples.…”