Organo-mineral Phases Research Articles

Developing an activated biochar-mineral supplement for reducing methane formation in anaerobic fermentation

Abstract The effects of biochar on methane emissions from soils are well understood. However, biochar effects on methane production from livestock have received less attention. In this study, a biochar-mineral supplement for livestock was developed by pyrolyzing a mixture of wheat straw, aluminosilicates, iron sulfate, and zinc oxide at 600 ℃. The supplement was then activated using peracetic and propionic acids, and potassium nitrate. The activated biochar-mineral supplement was characterized using analytical techniques. A high surface area, a high concentration of oxygen-containing functional groups, and a high concentration of free radicals, associated with O and Fe unpaired electrons, assisted the supplement with catalysing the oxidation of methane. Microstructural analysis of the supplement suggested the formation of organo-mineral phases, rich in C, O, Fe, Si, Al, K and Ca, indicating that the biochar reacted with mineral additives to preserve them. To assess the potential of the supplement to reduce methane produced form livestock, an in vitro batch culture incubation was conducted (n = 3) with rumen fluid sourced from Holstein–Friesian steers. The supplement was incubated at inclusion rates of 0% (control), 1.5%, 4.0% and 6.0% of dry matter (DM), with a Rhodes grass hay substrate. Compared to the control, the supplement reduced cumulative gas production by 10.1% and 12.7% and methane production by 19.03% and 29.32% after 48 h when included at 4.0% and 6.0% DM (P < 0.05), respectively, without causing any detrimental impacts on fermentation parameters. The supplement assisted with reducing the concentration of dissolved mineral nutrients, such as P and Mg, when included at 4.0% and 6.0% DM (P < 0.05). Graphical abstract

Interaction of fulvic acid with soil organo-mineral nano-aggregates and corresponding phosphate release

For more insight into the interaction of natural organic matter (NOM) with metal (hydr)oxides and oxyanions, the adsorption of added fulvic acid (FA) and the corresponding release of phosphate (PO4) were studied for a series of agricultural soils (∼0 – 25 cm), strongly varying in soil properties. Interpretation of the data with surface complexation modeling using the NOM-CD model applied in a dual-phase mode shows that the adsorption of added FA, in contrast to PO4, is restricted to the external surfaces of nano-aggregates. The adsorption is relatively weak and pH-independent, due to its competition with the native NOM of the organo-mineral phase. At low pH, the functional groups of both added FA and native NOM shift in the interface towards the soil oxide surfaces, making both a good competitor for adsorbed phosphate, resulting in a higher amount of phosphate being released. With an increase in pH, the competition becomes weaker. As a result, more phosphate is bound and less is released when FA is added. Our surface complexation modeling points to the existence of organo-mineral nano-aggregates with sizes of >∼10 – 270 nm, which depends on the total reactive surface area of the soil. Our findings imply that organic amendments containing FA equilibrate with only a portion of the total reactive surface area. In acidic soils, the addition of such organic amendments will be more effective in solubilizing phosphate, which is beneficial from a plant nutrition perspective, but simultaneously it may also contribute more to environmental eutrophication.

A Comparative Study of the Dynamic Fractionation of Rare-Earth Elements in Soils Using a Rotating Coiled Column and a Microcolumn

Rare earth elements (REEs) are currently used in fertilizers, but their behavior in the soil–plant system remains poorly studied. The assessment of the binding of REEs to various organomineral phases of soils remains an important task. Using soddy-podzolic soil and typical chernozem as examples, we performed a comparative study of the dynamic fractionation of REEs in a rotating coiled column (RCC) and a microcolumn (MC). We isolated the exchangeable fraction, specifically adsorbed fraction, and fractions bound to manganese oxides, bound to organic matter, and bound to amorphous and weakly crystallized iron and aluminum oxides using, 0.05 M Ca(NO3)2, 0.43 M CH3COOH, and a 0.1 M NH2OH·HCl solution (pH 3.6), a 0.1 M K4P2O7 solution (pH 11.0), and a 0.1 M (NH4)2C2O4 solution (pH 3.2), respectively. Concentrations of elements in the initial samples and eluate fractions were determined by atomic emission spectrometry and inductively coupled plasma mass spectrometry. The results suggest that the main extractable REE form (up to 40% of the total content) is provided by organometallic complexes extracted with a 0.1 M K4P2O7 solution. For chernozem (soils with a high content of organic matter), fractionation in the RCC and MC yielded comparable results. For soddy-podzolic soil, some differences were observed in the isolation of the first three fractions: exchangeable, specifically adsorbed, and bound to manganese oxides. Both RCC and MC can be successfully used for the dynamic fractionation of REE in soils; however, it is preferable to use an MC in analyzing many samples as a simpler and more affordable device.

Chemical weathering of mafic rocks in boreal subarctic environment (northwest Russia) under influence of glacial moraine deposits

Chemical weathering of mafic rocks represents substantial sink of atmospheric CO2 yet the mechanismes of this process in high-latitude regions are poorly understood. This work addresses geochemical migration and partitioning of major and trace elements between rock, soil and surface waters during chemical weathering of mafic rocks and soil formation under the influence of a glacial moraine in the northwestern Russian subarctic. We used multidisciplinary approach which included major and trace element chemical analysis, Sr isotopic measurements, and mineralogical structural and microscopic investigations. Quaternary (Pleistocene) deposits were observed even in the deepest horizons of soil profiles and confirm a strong moraine influence as most soils showed podzolic features. Chemical and Sr isotopic analyses revealed a strong impact of the moraine on soil chemistry and mineralogy. Mineralogical studies showed the presence of non-aeolian quartz and zircon in soils which were not linked to the nature of the parental rocks (i.e. mafic and felsic). At the same time, we observed the presence of etch pit corrosion on the surface of zircons and feldspars, and a newly-formed matter adjacent to the surface of primary phases. The chemical index of alteration (CIA) showed weak or no weathering of rocks within the soil profile and the weathering intensity scale confirmed the “felsic” chemical composition of soils developed over mafic and ultramafic rocks. Analysis of Sr radiogenic isotopes demonstrated preferential removal of easily weatherable and less radiogenic minerals over the full depth of soil profile and a more radiogenic signature of the granitic moraine compared to mafic and felsic bedrocks. The composition of most surface waters reflected the weathering of silicate rocks but did not allow for distinguishing purely mafic source. The chemical weathering rates of ultramafic rocks were calculated to be higher than those for the granitic till, but the moraine depositions which dominate this region hide evidence of the real weathering process. This could be due to retention of Mg and Ca in soil due to precipitation of secondary phases such as Mg-vermiculite or divalent cation adsorption on mineral, organic or organo-mineral phases. As a result, weathering rates estimated for the olivinite rock appear to be lower than the weathering rates of mafic rocks reported in other boreal and subarctic regions. Overall, the felsic moraine deposits are capable to sizably decrease the weathering intensity of mafic rocks which should be taken into account for chemical weathering modelling of high-latitude regions subjected to glaciation in the past.

Nanoscale analyses of the surface structure and composition of biochars extracted from field trials or after co-composting using advanced analytical electron microscopy

Biochars have been recognized as an important material to improve soil properties. In a number of studies their beneficial properties have been found to increase with residence time in soil and during the composting process. The beneficial properties have been correlated with surface functional groups resulting from the interactions between char particles, inorganic and organic matter in the soil and soil biota. These interactions result in the formation of organo-mineral phases on the internal and external surfaces of the biochar. A paucity of information exists, particularly from longer-term field trials, on organo-mineral phases present on both the internal and external surfaces of the biochar. To characterize the structure of, and interface between, the carbon and mineral phases, we examined biochars recovered from two field trials and after composting from different countries using high resolution scanning electron microscopy (SEM), atomic resolution transmission electron microscopy (TEM) and scanning TEM (STEM), energy electron loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDS) at resolutions of 1–20nm. The work revealed the formation of porous agglomerates of different minerals/inorganic compounds bound together with organic compounds on the surfaces of the biochar. In some cases, these agglomerates were bound together to form organo-mineral associations. The analyses also showed that the organic compounds containing both N and C functional groups and mixed valence iron oxide nanoparticles are possibly interacting with the organic compounds. The analysis also showed the formation of pores at the interface of the carbon matrix and organo-mineral aggregates.

Study on the Effect of Condensate-Type and Copolymer-Type Combined Superplasticizers on Hydration of Cement

For the limitation of single-component superplasticizer, condensate-type and copolymer-type combined superplasticizers were prepared. The adsorption of compound superplasticizers on cement paste was tested by Total Organic Carbon (TOC) measurement. Influences of superplasticizers on early hydration process of cement and Organo-mineral phase formation were studied by X-Ray Diffraction Analysis (XRD), Scanning Electron Microscope analysis (SEM) and so on. The results show that owing to the electrostatic repulsion and steric effect cooperative mechanism, condensate-type and copolymer-type combined superplasticizers reduce the superplasticizers adsorption in cement minerals and its hydration products surface, delay the process of hydration of C3A, form Organic-Layered double hydroxides (LDH), increase the early chemical shrinkage and promote the growth of cement early hydration and Ettringite

Formation of organo-mineral phases at early addition of superplasticizers: The role of alkali sulfates and C3A content

Most superplasticizers (SPs) exhibit significantly higher dispersing performance when added to an already mixed concrete (delayed mode) instead of addition with mixing water (early addition). Here, the specific parameters which determine this effect were investigated. At first, the tendency of four polycarboxylates and a naphthalene-polycondensate to intercalate into C3A hydrates was correlated with the flow values of pastes prepared from six different commercial cements at early and delayed addition. It was found that the contents of alkalisulfates and C3A present in the cement samples play the key role. For cements exhibiting a low alkalisulfate/C3A molar ratio (0.04–1.29), huge differences in paste flow at early and delayed addition were observed, presumably because of chemisorption (intercalation) of SP into C3A hydrates. While at high alkalisulfate/C3A molar ratios (~2), AFt (ettringite) is formed predominantly, and SP intercalation is impossible. Consequently, similar flow values are attained at early and delayed addition.

Occurrence of intercalation of PCE superplasticizers in calcium aluminate cement under actual application conditions, as evidenced by SAXS analysis

Intercalation of polycarboxylate (PCE) superplasticizers in calcium aluminate cement (CAC) during early hydration under both idealized and actual application conditions was confirmed by small-angle X-ray scattering (SAXS) analysis. The CaAl-PCE-LDHs were characterized by XRD, TEM, SEM and elemental analysis, and exhibited interlayer distances (d-values) ranging from 5 to 24nm, owed to the polydispersity of the PCE samples. Intercalating ability of the PCEs was dependent on their grafting density and anionicity, but was independent of their molecular weights. When highly anionic PCEs were utilized, significant amounts of nanocrystalline, colloidal intercalates were recovered, while few intercalates were detected when less anionic PCEs possessing high graft density were employed. Thus, contrary to OPC, less anionic PCEs disperse CAC better as little amount is wasted via intercalation, whereas higher dosages are required for more anionic PCEs, owed to abundant formation of organo-mineral phases. Finally, recommendations for reliable analysis of PCE intercalates in cement are given.

Thermal analysis as an express method for assessing the quality and quantity of natural and synthesized organoclays

New data on the energy stability of the structure of montmorillonite depending on the nature of organic compounds in natural and synthesized organoclays are reported. The organomineral phase was identified by specific features of the thermal effects in natural bentonite at the Tikhmenevka deposit. Montmorillonite was modified through intercalation with a cationic surfactant such as benzalkonium chloride by the ion exchange mechanism using a spiral mixer. The changes in the surface and structure of the obtained mineral and also the adaptability of molecules in the structure of modified montmorillonite were characterized by thermal gravimetric analysis (TGA). The data were used to calculate the optimum amount of modifier.

Influence of Dicyclopentadiene Co-Polymers on the Hardening Processes and Properties of Portland Cement Composites

Dicyclopentadine (DCPD) polymers can be used for the manufacture of self healing materials due to their ability to form in the presence of a catalyst a highly cross-linked polycyclopendiene. The DCPD polymers selected for this work contain also another constituent sequence (maleic anhydride), therefore in this paper we assess also the possibility to use it for a potential self healing process. In this paper is presented the influence of two types of (DCPD) co-polymers based on maleic anhydride copolymers on the hardening processes and main properties of portland cement pastes and mortars, as a first step in the development of a self-healing cementitious composite. The properties (mechanical strengths and volume variations) of the cementitious composites with DCPD co-polymers are influenced by the chemical structure of the obtained compounds and curing medium (dry or humid air). The mortars with AM (maleic anhydride/dicyclopentadiene co-polymer) did not develop any mechanical strength due to an important swelling phenomenon determined by the hydrolysis of anhydride groups and sterical modifications in chain structures. The presence of APA (AM copolymer modified with p-amino phenyl acetic acid) decreases the compressive strengths but has a less important effect on the flexural strength. The APA polymer-cement interaction consists in a chelatization process involving the nitrogen atoms and hydrogen bonding of carboxyl groups providing, in this case, a good cohesion of the composite material. For both polymers a delay in cement hydration was noticed at early ages as well as the formation of organo-mineral phases.

A SEM-EDS Study of Cultural Heritage Objects with Interpretation of Constituents and Their Distribution Using PARC Data Analysis

Two cultural heritage objects studied with scanning electron microscopy-energy dispersive spectroscopy (EDS) are presented in this article: (1) archeological iron present in a soil sample and (2) a chip from a purple-colored area of an undisclosed 17th century painting. Novel PARC software was used to interpret the data in terms of quantitative distribution of mineral and organo-mineral phases as well as their chemical composition. The study serves to demonstrate the power of PARC rather than solving specific archeological issues. The observations on archeological iron potentially can assist in (1) studing the source of iron-metal and the style of forging, (2) learning about alteration processes of artifacts in the particular soil from which the sample originated, and (3) determining the nature of the fractures in the Fe-oxide envelope (desiccation of the sample after excavation, or as primary feature caused by volume change from oxidation). In the paint chip, 11 consecutive layers can be distinguished using the PARC software. In general, each layer consists of a carrier supporting inorganic fragments. In the basal layer the fragments are dominant; in the superimposed layers the carrier usually is. Both organic and inorganic carriers appear to be present. Organic carriers can contain typically inorganic constituents (e.g., Pb, Al), beyond the chemical spatial resolution of EDS (i.e., <1 μm).

Fundamental mechanisms for polycarboxylate intercalation into C 3A hydrate phases and the role of sulfate present in cement

The fundamental reactions leading to the intercalation of polycarboxylate (PC) superplasticizers into calcium aluminum hydrates were studied by hydration of pure C 3A in the presence of PC at 75 °C. It was found that the amount of dissolved sulfate present in cement pore solution determines whether organo-mineral phases are formed or not. In the absence of sulfate, PCs easily intercalate during C 3A hydration in alkaline solution. Under these conditions, only excessive steric size of the PC will prevent intercalation. At low sulfate concentrations (SO 4 2−/C 3A molar ratios of 0.1–0.35), PC intercalates with intersalated alkali sulfate, are formed. At high sulfate concentrations (SO 4 2−/C 3A molar ratios of 0.7–2), PC can no longer intercalate. Instead, sulfate, because of its higher negative charge density, fills the interlayer space and monosulfoaluminates with different water contents are formed. Anion exchange experiments confirm that from the initially formed C 4AH 13, PC will exchange the interlayer OH − anion whereas with monosulfoaluminates, no replacement of sulfate by PC was found. Consequently, in alkaline solution, PC intercalates will not exchange their PC against OH − anions whereas sulfate will gradually replace the PC. Generally, intercalation of PC is an unwanted process because it consumes superplasticizer which is effective only when it adsorbs onto the cationic surfaces of AF m and AF t phases. Our experiments demonstrate that intercalation can be avoided by using PCs with long side chains or highly sulfated cements (SO 4 2−/C 3A molar ratio ≥ 0.75) containing alkali or calcium sulfates which dissolve fast. In undersulfated cements, however, PC intercalates can be formed, either directly during the stacking process of the [Ca 2Al(OH) 6] + main layer, with PC acting as the template which determines the interlayer distance, or by anion exchange between initially formed aluminate hydrates (e.g. C 4AH 13 or C 2AH 8) and the PC anion.

Effect of PCs superplasticizers on the rheological properties and hydration process of slag-blended cement pastes

The effect of polycarboxylate (PC) superplasticizers with different structure on the rheological properties and hydration process of slag-blended cement pastes with a slag content between 0 and 75% has been studied. Fluidizing properties of PCs admixtures are significantly higher in slag-blended cement with respect to non-blended Portland cement. Also, it has been observed that the rise of the fluidity induced by the PCs on the cement pastes increases with the slag content. This effect is mainly attributed to a decrease in the amount of C3A available to adsorb and consume admixture to form an organo-mineral phase. Consequently, the PC admixtures are absorbed onto the silicate phases of the clinker and onto the slag particles, inducing a repulsion and the concomitant reduction in yield stress despite a reduction in the zeta potential. The rheological results allow us to conclude that the highest increase of the fluidity is caused by the admixtures with highest molecular weight due to the higher steric repulsion induced. As a consequence of the adsorption of the PCs, a delay of the hydration process of the pastes has been observed.

Novel organo-mineral phases obtained by intercalation of maleic anhydride–allyl ether copolymers into layered calcium aluminum hydrates

The work presented here deals with the intercalation of worm- and brush-shaped polycarboxylates (PC) into calcium aluminum layered double hydroxide (Ca–Al-LDH). The nanocomposite materials were obtained from tricalcium aluminate hydration in presence of polycarboxylate copolymers with different side chain lengths. As polycarboxylate compound, amphiphilic copolymers composed of maleic anhydride and α-allyl-ω-methoxy-poly(ethylene glycol) ether with side chain lengths of n = 7, 10, 34, 70 and 90 ethylene oxide units (EOUs) were chosen. These polymers possess a high side chain density due to strictly alternating copolymerization. Powder X-ray diffraction (XRD) of the synthesized Ca–Al–PC-LDH composites revealed that basal spacings ( d-values) increase with the number n of EOUs in the side chain. An extremely high d-value of 4.85 nm was obtained for the polymer with n = 34 EOUs. According to elemental analysis data, the amounts of organic material present in the different composites were found to lie between 48 and 77 wt.%, respectively. Additionally, IR spectroscopy and thermogravimetric measurements were carried out in order to characterize the intercalates. The layered structure of the organo-mineral materials was confirmed by transmission electron microscopy (TEM).

A simplified view on chemical effects perturbing the action of superplasticizers

Understanding and quantifying effects of superplasticizers in concrete is a complex task. Even for nonreactive systems, such as ceramic suspensions, the stabilizing effects of dispersants are a subject of ongoing research. In cementitious systems, hydration reactions can perturb the behavior of suspensions. In this article, we propose three categories to describe the interactions and state of the superplasticizers with the cement suspensions. The first part would be consumed by intercalation, coprecipitation or micellization, i.e., by the formation of an organo-mineral phase (OMP). A second part of the polymer could be adsorbed onto the surface of particles and help disperse cement agglomerates. The third part consists of the excess superplasticizer neither consumed nor adsorbed and which remains dissolved in the aqueous phase. Thus, at equal dosage, a cement with a larger degree of consumption (Part 1) could have a lower surface coverage and consequently poorer workability (for cements otherwise equal: specific surface, composition, etc.), unless an excess of superplasticizer is added to ensure saturation. Differentiating consumption from adsorption is essential for correct interpretation of experimental data, a fact that is not yet appreciated often enough and to which this paper attempts to draw larger attention.

Preparation and application of organo-minerals as sorbents of phenol, benzene and toluene

Nonionic organic contaminants (NOCs) such as benzene, phenol, and toluene from contaminated wastewater can be effectively sorbed by organo-modified minerals. Organo-minerals were prepared from Na-montmorillonite, sericite, and zeolite by exchanging quaternary ammonium cations with various molecular weights such as Benzyldimethyltetradecylammonium (BDTDA), Hyamine 1622®, and Benzyltrimethylammonium (BTMA). The adsorption capacity of these organic cations onto these minerals is in the order of montmorillonite>zeolite>sericite, which is mainly dependent on the Ca/Mg cation exchange capacity (CEC) of each mineral. The interlayer expansion of the basal spacings of BDTDA- and Hyamine-montmorillonite increases from 12.5 to 30.8 Å as the amount of interlayer organic cation increases. BTMA-montmorillonite is characterized by less interlayer expansion. The aliphatic tale on the BDTDA ion apparently contributes to the multiple interlayer sorption in BDTDA in contrast to BTMA's reluctance to sorb a second interlayer. The exchange capacity of organic cations onto montmorillonite and the interlayer expansion of organo-montmorillonite correlate with the sorption of phenol, benzene, and toluene. BDTDA-, Hyamine-, and BTMA-montmorillonite complexes include benzyl functional groups and are effective sorbents for NOCs such as phenol, benzene, and toluene in aqueous solutions and may have practical applications in wastewater purification. The BTMA-zeolite complexes have potential for application as a sorbent for phenol. Organo-sericite complexes were the least effective sorbents of the three minerals tested. Comparison of the three NOCs with activated carbon indicates that these organo-mineral complexes all fall short of sorbing as did the activated carbon. BDTDA-montmorillonite stands out as the best performing product and it improved with each addition of surfactant to about 70% of the activated carbon sorption of benzene and 66% of toluene. BTMA-zeolite sorption was 65% of the sorption of the activated carbon for benzene and about 50% of the activated carbon sorption of toluene. Phenol was sorbed little on the untreated zeolite or sericite surfaces and poorly on the organo-mineral phases except that the BDTDA- and BTMA-montmorillonite sorbed about 35% as much phenol as sorption by activated carbon.

An examination of new procedures for fractionation of plutonium- and americium-bearing sediments

Sediment from the Ravenglass estuary has been fractionated by procedures which might be expected to bring about no change in the chemical forms of the bound plutonium and americium. The action of molten N-methylmorpholine- N-oxide (NMMNO) on the sediment extracts 20% of the 239Pu and 241Am, possibly in forms associated with humic-like materials. On dialysis, these extracts appear to lose 40% of the 239Pu and 20% of the 241Am. However, on pretreatment with base there is no significant loss of radioactivity on subsequent dialysis and this may indicate the existence of cationic forms of these elements. High gradient magnetic separation (HMGS) has fractionated the clay constituents (<0.2 μm and 0.2–2.0 μm) into three subfractions. From an analysis of the 239Pu/ 241Am ratio it would appear that there is no conservation of isotopic ratios; this might indicate that the environmental forms of 239Pu and 241Am exhibit markedly different affinities for the organo-mineral phases of the sediment.