Formation of Humic-Like Substances during the Technological Process of Lignohumate® Synthesis as a Function of Time

Abstract

The composition, structure, and biological activity of humic-like substances (HLS) synthesized in the process of lignosulfonate conversion for the production of the humic product Lignohumate® (LH) were examined. It is shown that during the hydrolytic-oxidative process, the transformation of raw material and accumulation of HLS occur. Data on the chemical (elemental content, functional groups, FTIR) and spectral (absorbance and fluorescence) parameters and biological activity (in phytotest) combined with PCA show that the LH samples can be divided into three groups, depending on the duration of synthesis: initial raw material (0-time sample); “young” HLS (15–30 min), and “mature” HLS in 45–120 min of treatment. During the first 30 min, reactions similar to the ones that occur during lignin humification in nature take place: depolymerization, oxidative carboxylation, and further polycondensation with the formation and accumulation of HLS. After 45–60 min, the share of HLS reaches a maximum, and its composition stabilizes. Biological activity reaches a maximum after 45–60 min of treatment, and at that stage, the further synthesis process can be stopped. Further processing (up to 2 h and more) does not provide any added value to the humic product.

Mechanical Properties and Formaldehyde Release of Particleboard Made with Lignin-Based Adhesives

“…A pronounced band at 1595 cm −1 may be assigned to aromatic skeletal vibration (originating from the aromatic C=C stretching). The band at 1512 cm −1 was assigned to skeletal vibration of lignin, while the band at 1453 cm −1 may be assigned to C-H deformation in aliphatic CH 3 and CH 2 groups, as observed by other researchers at 1465 cm −1 [62]. A weak band at 1421 cm −1 can be assigned to the C-H deformation in lignin and a band at 1332 cm −1 , which appears small as a shoulder, was found to belong to syringyl ring breathing [63], aliphatic O-H bending [64] or C-H in plane deformation of cellulose rings [65].…”

“…The band at 1160 cm −1 can be assigned to asymmetric -SO 2 -vibration, with reference to 1169 cm −1 corresponding to asymmetric (at 1169 cm −1 ) and symmetric (at 1142 cm −1 ) -SO 2 -vibrations [66], whereas a double band at 1143 cm −1 and 1169 cm −1 was assigned to binding vibrations in the aliphatic C-OH [63]. The 1114 cm −1 band is assigned to C-O-C vibration and 1034 cm −1 is assigned to C-O vibration of the phenolic OH [67] and/or -SO 3 H group [62], or Ar-O-C [35]. The peak at 646 cm −1 is assigned to S-O vibration in lignosulfonates.…”

Exolaccase-boosted humification for agricultural applications

“…One of the most important issues is the interaction mechanisms of artificial H-LPs and crop-soil-microbe in the rhizosphere. Based on the existing literature, the positive effects of artificial H-LPs on plant growth and crop productivity are reflected in the following 4 aspects ( Shah et al., 2018 ; Sun et al., 2022 ; Yang et al., 2021 ; Yakimenko et al., 2021 ). Artificial H-LPs profitably promote the absorption and metabolism of nutrients in crops ( Figure 8 ).…”