Amorphous Mineral Research Articles

Biocalcification in porcelaneous foraminifera.

Living organisms control the formation of mineral skeletons and other structures through biomineralization. Major phylogenetic groups usually consistently follow a single biomineralization pathway. Foraminifera, which are very efficient marine calcifiers, making a substantial contribution to global carbonate production and global carbon sequestration, are regarded as an exception. This phylum has been commonly thought to follow two contrasting models of either in situ 'mineralization of extracellular matrix' attributed to hyaline rotaliid shells, or 'mineralization within intracellular vesicles' attributed to porcelaneous miliolid shells. Our previous results on rotaliids along with those on miliolids in this paper question such a wide divergence of biomineralization pathways within the same phylum of Foraminifera. We have found under a high-resolution scanning electron microscopy (SEM) that precipitation of high-Mg calcitic mesocrystals in porcelaneous shells takes place in situ and form a dense, chaotic meshwork of needle-like crystallites. We have not observed calcified needles that already precipitated in the transported vesicles, what challenges the previous model of miliolid mineralization. Hence, Foraminifera probably utilize less divergent calcification pathways, following the recently discovered biomineralization principles. Mesocrystalline chamber walls in both models are therefore most likely created by intravesicular accumulation of pre-formed liquid amorphous mineral phase deposited and crystallized within the extracellular organic matrix enclosed in a biologically controlled privileged space by active pseudopodial structures. Both calcification pathways evolved independently in the Paleozoic and are well conserved in two clades that represent different chamber formation modes.

Chiral gypsum with high‐performance mechanical properties induced by self‐assembly of chiral amino acid on an amorphous mineral

AbstractFunctional chiral suprastructures are common in biology, including in biomineralization, and they are frequently found in many hardened structures of both marine and terrestrial invertebrates, and even in pathologic human otoconia of the inner ear. However, the biological processes by which they form remain unclear. Here, we show that chiral hierarchical suprastructures of calcium sulfate dihydrate (gypsum) can be induced by the chiral Aspartic acid (Asp). Left‐handed (clockwise) morphology of gypsum is induced by the d‐enantiomer of Asp, while right‐handed (counterclockwise) morphology is induced by the l‐enantiomer. A layer‐by‐layer, oriented inclination mineral growth model controlled by continuous self‐assembly of chiral Asp enantiomers on an amorphous calcium sulfate mineral surface of gypsum platelet layers is postulated to produce these chiral architectures. This hybrid amorphous‐crystallized chiral and hierarchical suprastructure of gypsum displays outstanding mechanical properties, including high‐performance strength and toughness. Furthermore, the induction of chiral gypsum suprastructures can be more generally extended from specific acidic amino acids to other (nonamino acid) molecules. These findings contribute to our understanding of the molecular mechanisms by which biomineral‐associated enantiomers exert structural control over chiral architectures commonly seen in biominerals and in biomimetically synthesized functional materials.

Mineral Fusion via Dehydration‐Induced Residual Stress: From Gels to Ceramic Monoliths

AbstractMan‐made ceramics generally undergo harsh manufacturing conditions (e.g., high‐temperature sintering). In contrast, mineral structures with superior mechanical strength are generated in organisms under mild biocompatible conditions. Herein, it is reported that ceramic objects can be directly produced and strengthened by drying purely inorganic gels (PIGs), mimicking the biological tactic of fabricating continuous monoliths from hydrated amorphous precursors. The overall process is easy and biocompatible in that solutions of common iron and molybdate salts are mixed to generate a PIG, consisting of 80 wt% liquid water and amorphous mineral nanoparticles (hydrated iron molybdate: FeMo2H7O11), which, upon drying under mild temperature, turns into a residual stress‐strengthened ceramic block that displays a high mechanical performance (with a hardness/elastic modulus of 1.7/17.5 GPa). Analogous to the well‐known Prince Rupert's drop reinforced by residual stress upon quenching, the uneven volume shrinkage from the outside inwards during dehydration builds up residual stress that enables amorphous mineral fusion (with the assistance of hydration water) and strengthening. Furthermore, a dramatic bandgap reduction is achieved in the dried objects due to local structural changes of the Fe atoms under residual stress. This PIG‐dehydration approach holds promise for green ceramic manufacturing and offers insights into biomineralization puzzles.

Experimental investigation on thermal modification and burnout of residual carbon in coal gasification fine slag

Disposal of coal gasification fine slag (CGFS) has caused environmental pollution and resource waste. Its decarbonization is the bottleneck of aluminum and silicon resource utilization. A fluidization-melting combustion system is proposed in this study to realize the decarbonization. The fluidized thermal modification and burnout characters of residual carbon in CGFS were investigated experimentally on a bench-scale test rig. A two-stage decarburization path of CGFS was concluded and verified. The fluidized modification of CGFS is first conducted to decrease the particle size and improve the specific surface area and combustion reactivity. So, the modified exposed carbon in CGFS rapidly burns in the melting furnace to generate the condition above the fluid temperature of minerals. Then the mineral shell of the amorphous mineral covered carbon in CGFS is molten and damaged, and the carbon appears and burns out. The decrease in the thermal modification temperature induced deceases in melting combustion temperature and decarbonization efficiency. Efficient decarbonization of CGFS produced by three different entrained bed gasifiers was realized by the fluidization-melting combustion, the decarburization efficiencies are all above 95% and the comprehensive carbon contents of ash and slag are all below 5%.

Effects of long-term application of inorganic fertilizer and organic amendments on the amounts of fractionated soil organic carbon and their determining factors in paddy fields

ABSTRACT To investigate how the long-term application of inorganic fertilizer and organic amendments affects the accumulation of organic matter in physico-chemically fractionated components in paddy soils and how the accumulation is determined by soil properties and anthropogenic carbon input, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the amounts of accumulated soil organic carbon (SOC) in fractionated components in three paddy fields. SOC was fractionated into four components based on their physical and chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. On average, the amount and percentage of accumulated C in the four fractions were as follows: OxF (6.63 gC kg−1 soil, 46%) > NOxF (5.32, 35) > LF (1.68, 12) > HF (1.12, 7.2), suggesting about 80% of SOC was in fine, stable fractions. The amount of accumulated C in all fractions increased slightly with the application of inorganic fertilizer, while it increased considerably with the use of organic amendments. In addition, the application of fertilizers and amendments raised the proportion of C content in LF and HF, which are labile and related to soil fertility. Stepwise multiple regression analysis using two principal component analysis scores of soil properties and anthropogenic C input further revealed that the labile fractions (LF and HF) were more strongly determined by the management of fertilizers and amendments, while the stable fractions (OxF and NOxF) were more strongly determined by soil-specific properties, mainly the amorphous nature of the soil. These results indicate that the use of certain amounts of organic amendments would be recommended to carry out rational management to improve soil fertility and C sequestration in paddy fields, with the application of amorphous minerals as an additional option.

Crystal induced arthropathies-a comparative study of 40 patients with apatite rheumatism, chondrocalcinosis and primary synovial chondromatosis.

Introduction: Apatite rheumatism (AR), chondrocalcinosis (Ch-C), and primary synovial chondromatosis (prSynCh) are regarded as distinct clinical entities. The introduction of the non-staining technique by Bély and Apáthy (2013) opened a new era in the microscopic diagnosis of crystal induced diseases, allowing the analysis of MSU (monosodium urate monohydrate) HA (calcium hydroxyapatite), CPPD (calcium pyrophosphate dihydrate) crystals, cholesterol, crystalline liquid lipid droplets, and other crystals in unstained sections of conventionally proceeded (aqueous formaldehyde fixed, paraffin-embedded) tissue samples. The aim of this study was to describe the characteristic histology of crystal deposits in AR, Ch-C, and prSynCh with traditional stains and histochemical reactions comparing with unstained tissue sections according to Bély and Apáthy (2013). Patients and methods: Tissue samples of 4 with apatite rheumatism (Milwaukee syndrome), 16 with chondrocalcinosis, and 20 with clinically diagnosed primary synovial chondromatosis were analyzed. Results and conclusion: Apatite rheumatism, chondrocalcinosis, and primary synovial chondromatosis are related metabolic disorders with HA and CPPD depositions. The authors assume that AR and Ch-C are different stages of the same metabolic disorder, which differ from prSynCh in amorphous mineral production, furthermore in the production of chondroid, osteoid and/or bone. prSynCh is a defective variant of HA and CPPD induced metabolic disorders with reduced mineralization capabilities, where the deficient mineralization is replaced by chondroid and/or bone formation. The non-staining technique of Bély and Apáthy proved to be a much more effective method for the demonstration of crystals in metabolic diseases than conventional stains and histochemical reactions.

CPPD and Associated Crystals in Clinically Diagnosed Chondrocalcinosis: A Clinicopathological Study of 20 Patients

Introduction: Chondrocalcinosis (Ch-C), induced by calcium pyrophosphate dihydrate crystals (CPPD) [Ca2P2O7.2H2O] is considered as a distinct metabolic disease and a well-defined clinical entity, with characteristic clinical manifestations and symptoms. This study used previously found method by the author .i.e, non-staining approach to discover crystal deposits in patients with clinically diagnosed Ch-C, to find a possible correlation between coexisting crystals, and to assess the role of coexistent crystals in inflammatory cellular processes of joints. Patients and methods: There were forty (40) surgical specimens that had been traditionally processed from 16 patients who had been clinically diagnosed with Ch-C. Results: In unstained tissue sections CPPD crystals were found in 22 of 40 samples of all 16 patients. Beside the CPPD crystals calcium hydroxyapatite (HA) [Ca5(PO4)3(OH)] crystals were found in 26 tissue samples of all 16 patients, cholesterol (CC) [C27H46O] in 23 tissue samples of 12 patients, and crystalline liquid lipid droplets (CL) in 11 tissue samples of 5 patients. More or less amorphous deposits of calcium carbonate [CaCO3] and/or calcium phosphate [Ca3(PO4)2] were present alongside CPPD and the contemporaneous crystals. There was a significant and positive correlation between prevalence of CPPD and HA. The connection between inflammatory cellular infiltration and CPPD, HA, CC or CL crystals surrounded by mineral deposits was not significant. Conclusions: The non-staining approach is a practical, low-tech way to find CPPD, HA, CC, and other crystals (with or without CL). The positive and significant correlation between CPPD and HA support the earlier premise that CPPD and HA represent basically an identical metabolic disorder). CPPD and/or HA crystals can provoke inflammatory processes responsible for the clinical symptoms, but the variable amounts of amorphous minerals enclose (isolate) the crystals, and can reduce or eliminate the inflammatory reaction. The authors assume that CC (with or without CL) is an associated phenomenon (concomitant fat metabolic malady) without direct cause of inflammation, and is not responsible for clinical symptoms of crystal induced arthropathies.

Amorphous 1-D nanowires of calcium phosphate/pyrophosphate: A demonstration of oriented self-growth of amorphous minerals

Amorphous inorganic solids are traditionally isotropic, thus, it is believed that they only grow in a non-preferential way without the assistance of regulators, leading to the morphologies of nanospheres or irregular aggregates of nanoparticles. However, in the presence of (ortho)phosphate (Pi) and pyrophosphate ions (PPi) which have synergistic roles in biomineralization, the highly elongated amorphous nanowires (denoted ACPPNs) form in a regulator-free aqueous solution (without templates, additives, organics, etc). Based on thorough characterization and tracking of the formation process (e.g., Cryo-TEM, spherical aberration correction high resolution TEM, solid state NMR, high energy resolution monochromated STEM-EELS), the microstructure and its preferential growth behavior are elucidated. In ACPPNs, amorphous calcium orthophosphate and amorphous calcium pyrophosphate are distributed at separated but close sites. The ACPPNs grow via either the preferential attachment of ∼2 nm nanoclusters in a 1-dimension way, or the transformation of bigger nanoparticles, indicating an inherent driving force-governed process. We propose that the anisotropy of ACPPNs microstructure, which is corroborated experimentally, causes their oriented growth. This study proves that, unlike the conventional view, amorphous minerals can form via oriented growth without external regulation, demonstrating a novel insight into the structures and growth behaviors of amorphous minerals.

Using a novel approach to characterize the surface reactivities of silica-rich ferrihydrite and biogenic cyanobacteria-ferrihydrite aggregates and the implications for Archean ocean geochemistry

Precambrian banded iron formations (BIF) are iron- and silica-rich chemical sedimentary rocks that are commonly used as paleo-redox proxies for Archean and Paleoproterozoic seawater geochemistry. At the onset of the Great Oxidation Event (herein GOE) around 2.4 Ga, cyanobacteria flourished with increasing nutrient fluxes due to oxidative weathering on land. In turn, this led to increased primary productivity that facilitated the permanent shift from a reducing Earth atmosphere to an oxidizing one. Interestingly, the duration of GOE also overlapped with one of the most prolific periods of BIF deposition.It is widely accepted that cyanobacteria were likely responsible for BIF formation during the GOE. Oxidation of dissolved Fe(II) by oxygen produced from cyanobacteria forms a metastable and amorphous mineral phase ferrihydrite, Fe(OH)3. As an essential component in both ancient BIF deposits and various modern ecosystems, the surface reactivity of ferrihydrite has been extensively studied under different conditions (i.e., pH and ionic strengths). Not only are the highly reactive surfaces of ferrihydrite particles important shuttles for trace element transport from the water column to the sediment pile, but previous studies have also demonstrated that cyanobacterial cells and ferrihydrite tend to aggregate at seawater pH. This means that ferrihydrite was also a vector for the transport of organic carbon to the seafloor. However, a complicating issue is how co-ions affect the surface reactivity of ferrihydrite, specifically dissolved silica which was abundant in ancient seawater. Although previous studies have demonstrated that silica can passivate the surface reactivity of ferrihydrite, what remains unclear is how silica impacts ferrihydrite-biomass aggregation. To fill this knowledge gap, we formed both silica-spiked ferrihydrite and cyanobacteria-ferrihydrite aggregates in situ and subsequently conducted empirical potentiometric acid-base titrations and Cd adsorption experiments on the fresh aggregate samples at three different ionic strengths (0.56 M, 0.1 M and 0.01 M). We minimized sample processing (i.e., drying and powdering) to a simple washing step, in which the aggregate pellets remained hydrated to avoid any mineral transformation thus altering their true surface reactivity in seawater. Experimental results were then fitted with non-electrostatic model to predict both surface charges and metal-adsorption behavior of ferrihydrite aggregates. Different from previous surface-complexation modelling studies, here we used a novel and more powerful modelling program called Phreefit. It utilizes the global optimization algorithms instead of more commonly used Newton-Raphson method in FITEQL program, which is often too limited for precisely modelling complex systems such as the two samples in this study. Furthermore, we also measured the surface charges of both samples over the pH range from 3 to 9 on a Malvern Zetasizer and characterized the surface functional groups through Fourier-Transform Infrared Spectroscopy to help with our interpretation of the experimental data.Preliminary results show that cyanobacteria-ferrihydrite aggregates formed primarily due to ionic bridging. Cyanobacterial cells likely facilitated the precipitation of dissolved silica. Findings from titration and Cd adsorption experiments indicate that the surface reactivity and capacity of both silica-rich ferrihydrite cyanobacteria-ferrihydrite aggregates to adsorb trace elements differ from their individual components, likely due to site blockage. This distinction is particularly prominent when considering the expected Archean seawater pH from 6 to 8. This disparity implies that the biogenic ferrihydrite aggregates do not exhibit an additive surface reactivity, which is in agreement with similar previous studies. Our combined results are crucial to accurately predict the adsorption of trace elements onto the aggregate surface and, ultimately, comprehend the archive of trace elements in sedimentary rocks used to reconstruct Precambrian ocean chemistry.

Relating mineral-organic matter stabilization mechanisms to carbon quality and age distributions using ramped thermal analysis.

Organic carbon (OC) association with soil minerals stabilizes OC on timescales reflecting the strength of mineral-C interactions. We applied ramped thermal oxidation to subsoil B horizons with different mineral-C associations to separate OC according to increasing temperature of oxidation, i.e. thermal activation energy. Generally, OC released at lower temperatures was richer in bioavailable forms like polysaccharides, while OC released at higher temperatures was more aromatic. Organic carbon associated with pedogenic oxides was released at lower temperatures and had a narrow range of 14C content. By contrast, N-rich compounds were released at higher temperatures from samples with 2 : 1 clays and short-range ordered (SRO) amorphous minerals. Temperatures of release overlapped for SRO minerals and crystalline oxides, although the mean age of OC released was older for the SRO. In soils with more mixed mineralogy, the added presence of older OC released at temperatures greater than 450°C from clays resulted in a broader distribution of OC ages within the sample, especially for soils rich in 2 : 1 layer expandable clays such as smectite. While pedogenic setting affects mineral stability and absolute OC age, mineralogy controls the structure of OC age distribution within a sample, which may provide insight into model structures and OC dynamics under changing conditions. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.

Mechanical activation of coal gasification fine slag and mechanical and thermal properties of coal gasification fine slag–poly(vinyl chloride) composites

To facilitate the high-value utilization of activate coal gasification fine slag (CGFS), a wet mechanical activation process was used. As a result of this treatment, CGFS samples with different particle size distributions were obtained. The effects of mechanical activation on various physical and chemical properties of CGFS were investigated, including its particle size distribution, mineral composition, specific surface area, pore size, crystallinity, particle morphology, chemical bonding, and binding energy. Poly(vinyl chloride) (PVC)/CGFS composites were prepared via a melt blending process, and their mechanical and thermal properties were evaluated. It was found that with increasing levels of mechanical activation, the CGFS particle size distribution became more concentrated and the particle spacing became more uniform. With the increasing mechanical activation, the crystallinity was found to decrease and the content of amorphous mineral matter (such as SiO2 and Al2O3) increased. The observed increase in specific surface area and decrease in average pore diameter due to the mechanical activation was seen to lead to an increase in the number of active sites. The produced PVC/CGFS composite materials were found to exhibit good mechanical properties and dynamic thermal stability. The thermal stability of the PVC composites was also found to improve relative to the composites produced without the use of mechanical activation.

Journey of Mineral Precursors in Bone Mineralization: Evolution and Inspiration for Biomimetic Design.

Bone mineralization is a ubiquitous process among vertebrates that involves a dynamic physical/chemical interplay between the organic and inorganic components of bone tissues. It is now well documented that carbonated apatite, an inorganic component of bone, is proceeded through transient amorphous mineral precursors that transforms into the crystalline mineral phase. Here, the evolution on mineral precursors from their sources to the terminus in the bone mineralization process is reviewed. How organisms tightly control each step of mineralization to drive the formation, stabilization, and phase transformation of amorphous mineral precursors in the right place, at the right time, and rate are highlighted. The paradigm shifts in biomineralization and biomaterial design strategies are intertwined, which promotes breakthroughs in biomineralization-inspired material. The design principles and implementation methods of mineral precursor-based biomaterials in bone graft materials such as implant coatings, bone cements, hydrogels, and nanoparticles are detailed in the present manuscript. The biologically controlled mineralization mechanisms will hold promise for overcoming the barriers to the application of biomineralization-inspired biomaterials.

Synthesizing alkali-activated binder from locally available sedimentary rock as precursors

Significant research efforts have been made recently to broaden the selection of precursors for alkali-activated binders, especially to utilize the locally available resources. This study presents the experimental investigation of utilizing sedimentary rocks rich in silica and alumina excavated during the construction of Jurong Rock Caverns in Singapore for alkali-activated binders. The precursors were synthesized by calcinating rock powder mixed with alumina and sodium hydroxide. The crystalline structure of the quartz and albite was broken after being subjected to calcination, and disordered, amorphous minerals were formed. The influence of the initial Si/Al and Na/Al molar ratios on the chemical composition and reactivity was investigated. The degree of polymerization decreased with the increase in the alumina and sodium hydroxide content. Higher alumina content also promoted the formation of aluminosilicate crystals during the cooling process, which reduced the reactivity of the precursors. The compressive strength of the alkali-activated binder was found to be dependent on the concentration of the soluble Si and Al released during alkali activation. Overall, the excavated sedimentary rocks could be used as potential precursors in alkali-activated binders.

Interdependence between bacterial EPS and early grain coat development

AbstractBacteria are the most abundant forms of life we know on our planet, able to survive in a variety of habitats, that play an important role in mineral formation and transformation processes. Here, we present laboratory experiments in which unconsolidated quartz grains were seeded with Geobacter sulfurreducens cells and exposed to a mineral medium solution for 96 hours at temperatures of between 60°C and 120°C. Experimental data show the interdependence between extracellular polymeric substances (EPS) and the early formation of grain‐coating material. The occurrence of EPS promotes the development of web and bridging structures binding the quartz grains and creating EPS‐coated surfaces. With increasing temperature, an amorphous mineral phase grows preferentially on these surfaces suggesting that EPS can act as a template for mineral nucleation. At temperatures >100°C, the order of crystallinity of the amorphous authigenic phase increases, transitioning to poorly‐ordered rosette‐like textures.

Flexible design in the stomatopod dactyl club.

The stomatopod is a fascinating animal that uses its weaponized appendage dactyl clubs for breaking mollusc shells. Dactyl clubs are a well studied example of biomineralized hierarchical structures. Most research has focused on the regions close to the action, namely the impact region and surface composed of chitin and apatite crystallites. Further away from the site of impact, the club has lower mineralization and more amorphous phases; these areas have not been as actively studied as their highly mineralized counterparts. This work focuses on the side of the club, in what is known as the periodic and striated regions. A combination of laboratory micro-computed tomography, synchrotron X-ray diffraction mapping and synchrotron X-ray fluorescence mapping has shown that the mineral in this region undergoes the transition from an amorphous to a crystalline phase in some, but not all, clubs. This means that this side region can be mineralized by either an amorphous phase, calcite crystallites or a mixture of both. It was found that when larger calcite crystallites form, they are organized (textured) with respect to the chitin present in this biocomposite. This suggests that chitin may serve as a template for crystallization when the side of the club is fully mineralized. Further, calcite crystallites were found to form as early as 1 week after moulting of the club. This suggests that the side of the club is designed with a significant safety margin that allows for a variety of phases, i.e. the club can function independently of whether the side region has a crystalline or amorphous mineral phase.

Exploitation of waste perlite products in lime-based mortars and grouts

Perlite is an amorphous mineral, coming from volcanic deposits and mainly consists of alumino-siliceous compounds. Perlite mining presents a low environmental burden, while during the last 60 years less than the 1% of the worldwide reserves have been exploited. During its industrial process, a significant number of secondary products derives and remain unexploited, inducing the environmental burden. The study focuses on exploiting two secondary products coming from the elaboration of perlite (named after D1S, D1C), in the Hellenic plant. These products have been used as pozzolans in the production of mortars and grouts. During the experimental part, nine mixtures where manufactured and tested, including five mortars and four grouts, where natural pozzolan was substituted by D1S and D1C. The fresh state properties of all mixtures were recorded, as well as their hardened ones, including shrinkage deformations, porosity, apparent specific gravity, water absorption coefficient due to capillary action, dynamic modulus of elasticity, flexure and compressive strength. From the correlation of the results, it was asserted that the partial or even total substitution of natural pozzolan by perlite secondary products, can positively influence the physical and mechanical properties of the composites. D1S seem to be an alternative pozzolanic material leading in mortars and grouts of enhanced properties. It maybe therefore concluded that the exploitation of perlite secondary products in the construction sector is feasible, leading to the development of effective, low-cost and environmentally friendly products for specific applications.

Effect of Fertilization and Agricultural Amendments on the quality of a Prairy Established on a Volcanic Soil, Andosol

This research was established at El Prado-IASA1 farm, Agricultural Engineering Career, on a soil of volcanic origin of the Andisol order, in order to evaluate the quality of the forage due to the effect of chemical fertilization and four amendments: lime (E1), gypsum (E2), magnesium silicate (E3) and phosphate rock (E4), mixed amendment (EM) and two level of NPK fertilization. These treatments were applied in an established meadow with: kikuyo (Pennisetum clandestinum), blue grass (Dactylis glomerata), perennial rye grass (Lolium perenne) and white clover (Trifolium repens). The amendments and fertilization were incorporated after the first cut, in an amount equivalent to 1500 of lime, 500 of gypsum, 300 of magnesium silicate and 300 of phosphate rock kg ha-1 year-1, plus fertilization F1: N100-P50-K50 and F2: N300-P100-K100, fractionated for 10 cuts per year. The variables evaluated were: green mass production, dry matter, macro and micronutrient soil content. The forage assessment was based on the physiological growth of rye grass as a dominant prairie species. The results positively affected the quality and production of forage in t ha-1, due to the effect of lime, phosphate rock, and NPK fertilization. There was a high fixation of NH4, K, and P, due to the effect of amorphous minerals, high Fe content, and water deficit. Hence it is recommended to keep close to the soil's field capacity level.

Geopolymerization kinetics of steel slag activated gasification coal fly ash: A case study for amorphous-rich slags

The geopolymer processing of amorphous-rich slag required excessive soluble alkali usage severely limiting the application of geopolymer materials. In this study, industrial solid waste steel slag (SS) was introduced as alkali substitution for stimulating the potential activity of Shell gasification coal fly ash (SFA). Result shows that a 15%–20% addition of SS can reduce 14.5–23.3% NaOH consumption for the preparation of high-strength geopolymers. SS accelerates the dissolution rate of SFA promoting the early strength of geopolymer (ES) via alkalinity adjustment and reducing the wetting angle of refactoring globular particles in the slurry. The long-term strength of geopolymer (LS) is increased to 68.5 MPa with the higher devotion of SFA (67 ω%). During the geopolymerization course, Ca-rich hydrates growth are competed with the polymerization of amorphous minerals. The geopolymerization kinetics enlightens that the soluble tetrahedral SiO4 or AlO4 and hydrates in pozzolanic phase initially generated in paste then transformed to a more stable form of amorphous phase after a series of repeated processes of dissolution, homogeneous nucleation, and heterogeneous growth. This work paves a environmentally friendly way for disposing amorphous-rich slags with low activity and discloses the detailed mechanism of related geopolymerization.

Competitive adsorption of phosphate with sulfate, humic acid, and fulvic acid by allophane in different parent materials in Central Java

Andisol is a soil that has andic properties and develops from volcanic parent materials, especially ash. Andic soil properties are formed due to weathering of tephra or other parent materials that contain volcanic glass in large quantities. The main components of soil-forming Andisol are amorphous (short-range-order) minerals, such as allophane, imogolite, ferrihydrite, and Al/Fe-humus complexes. The existence of short-range-order minerals causes Andisol to have high P-tapping ability, but efforts to lower the amount of P plunged with organic and inorganic an-ons have not been widely studied. This study aimed to compare the ability of humic acid, fulvic acid, and sulfate in suppressing P adsorption by amorphous minerals from the Andisol of Mount Dieng, Merbabu, and Sumbing. The highest calculation of % ferrihydrite was found at the location of Mount Merbabu with a value of 3.05%, while the % allophane + imogolite was determined by the content of Sio in the ground. The calculation results showed that the highest was found at the location of Mount Sumbing with a value of 7.17%. Based on TEM analysis, Mount Sumbing has allophane diameter of 2.24 – 5.93 nm and the imogolite length of 24 – 187 nm.

Adsorption and release of soil P in andisols under organic and conventional vegetable farming system

Phosphorous (P) is strongly adsorbed by soil components, such as soil organic matter and soil amorphous minerals in Andisols, which have been identified as an influential factor in adsorption and release of soil P. The aim of this study was to characterize the pattern of soil P adsorption and release in both organic and conventional vegetable farming systems in Merbabu Mountain area, Indonesia. Soil samples were collected from soil layers (0 cm to 20 cm and 20 cm to 40 cm) in organic and conventional farming systems. The result showed that the highest adsorption rate was found in organic farming systems at a depth of 20 cm to 40 cm. The lowest adsorption rate was found in conventional farming systems with low input of organic matter at a depth of 20 cm to 40 cm. A higher rate of P release was also found in organic farming systems with a low input of organic matter. It can be concluded that vegetable soils in organic farming systems are not only highly capable of adsorbing P but also capable of releasing P rapidly.