Characterization of humic acids extracted from biosolid amended soils

13 páginas.-- 8 figuras.-- 5 tablas.-- 36 referenciasThe aim of this study was to evaluate the changes produced in the chemical, acid-base and structural properties of soil amended (biosolids) and humic acids HAs incubated at different times. In the current work the amendments were conducted with biosolids at different doses (30, 90 and 180 t ha-1) on Colina (CLN) soil for 1, 2, 4 and 6 months. The acid-base characterization of extracted humic acids (HAs) showed a slight impact on Atotal (total acidity, mEq g-1), at 30 and 90 t ha-1 while at 180 t ha-1 the greatest increase was observed from 10.5±1.61 (control) to 17.9±0.30 (6 months of incubation). without evolution over the incubation time. The Aphenolic (phenolic acidity, mEq g-1) acidity behaves similarly while Acarboxylic (carboxylic acidity mEq g-1)) remains constant over time and applied doses. The application of 13C solid state NMR technique revealed higher abundance of aromatic C (CLN 43.5%) over alkyl C (21.4%) compounds. Aromatic C presents a decrease at high biosolid doses, which occurs simultaneously with alkyl C increase when using the same surveyed doses. Therefore, it might be considered that through the addition of biosolids, components such as fatty acids, amino acids or paraffinic structures are incorporated. As a result of biosolids addition, carboxylic C content remains steady, which agrees with the Accarboxylic behavior previously determined.the funding provided by CONICYT through project Fondecyt 1130094.Peer reviewe

Surfactant properties of humic acids extracted from volcanic soils and their applicability in mineral flotation processes

7 páginas.-- 5 figuras.-- 3 tablas.-- 30 referenciasSurface Tension (ST) of water solutions of humic acids extracted from volcanic ash derived soils (soil humic acids, S-HA), were measured under controlled conditions of pH (13.0), temperature (25 °C) and ionic strength (NaOH 0.1M) to establish the Critical Micellar Concentration (CMC). All S-HA were characterized by elemental analysis, acid-base titration, Transmission Electronic Microscopy (TEM) micrographs, isoelectric point (IEP) and solid state 13C-NMR. After that, these humic acids were evaluated as potential biomaterials to be used in mineral flotation processes, where a series of experiments were conducted at different S-HA and molybdenite ratio (from 0.2 to 50 g ton−1) establishing the IEP of all resultant materials. The use of solid state 13C-NMR enabled the following sequence of intensity distribution areas of S-HA to be established: O/N Alkyl>Alkyl C>Aromatic C>Carboxyl. The experimental values of ST and the calculated CMC (ranging from 0.8 to 3.3 g L−1) revealed that for S-HA no relationship between the abundance groups and their behavior as surfactant materials was observed. In relation with IEP determined for all materials, the highest surface charge, which can be useful for flotation processes, was obtained with 0.2 g of S-HA per ton of molybdenite. Additionally, TEM studies confirm the formation of pseudoaggregates for all the S-HA considered. Finally, the S-HA could be considered as an alternative to chemical products and commercial humic acids materials in mineral flotation processes.Support from FONDECYT, Chile project 1130094, DIPOG 3913-529-81, Basal Funding for Scientific and Technological Centers of Excellence FB0807 CEDENNA and CONICYT PIA/ANILLO, ACM170002 are kindly acknowledgedPeer reviewe

Influence of inorganic additives on wheat straw composting: Characterization and structural composition of organic matter derived from the process

10 páginas.- 3 figuras.- 6 tablas.- referencias.-Metallic oxides and clay minerals have gained increasing interest as additives of composting due to their influence in greenhouse gas emissions reduction and their effectivity in the stabilization of carbon both in compost and soils, leading to a cleaner compost production and potentially C sequestrant amendments. In this study, wheat straw (WS) was co-composted with iron oxide and allophanic soil and their influence on WS composting and composition of the end-products was evaluated. WS compost and their humic like-substances (HS) fraction were characterized by chemical and spectroscopic analyzes. After 126 days of process, the elemental composition showed slight differences of the N content for compost and HS, where the C/N atomic ratio tended to decrease relative to the initial material (WS; ~130). This trend was more pronounced in the HS from co-composted treatments (<30). The addition of inorganic materials increased the total acidity and phenolic-OH group contents (~15 and 14 mEq g−1 respectively, iron oxide treatment) relative to the treatment without inorganic additives. Nevertheless, the FTIR and solid-state 13CNMR spectroscopy barely support the wet chemical analysis and revealed a similar final composition between all the studied compost treatments. These results suggest that the incorporation of these materials as compost additives had no major effect on the spectroscopic features of the end-products, however, critical changes of the properties such as the extractability, functionality and composition of HS were revealed by traditional methods. In conclusion, the supply of metal oxides and clays could impact the aerobic composting of WS favorizing the stabilization of certain C pools and adsorptive properties of the end-products, that is of importance in production of amendments suitable for being used in degraded and contaminated soils. Nevertheless, under the experimental conditions of our research C stabilization apparently depends of other mechanisms that still need to be elucidate.The authors thank the Comisión Nacional de Investigación Científica y Tecnológica (CONICYT-Chile), for the economic support through the program CONICYT/FONDECYT/1170264 and CONICYT/FONDAP/15130015 (P. Cornejo). H. Knicker thanks the Ministerio de Ciencia, Innovacion y Universidades of Spain and the European Regional Development Fund for financial support through the project CGL2015-64811-P. J. Medina and M. Calabi-Floody thanks CONICYT for the financial support through the CONICYT/FONDECYT/3170677 grant and CONICYT/FONDECYT/11150555 grant, respectively. M. Antilén and P. Cornejo also thank CONICYT for the economic support through the project CONICYT-PIA Rings in Mining Topics ACM170002.Peer reviewe