Surface Of Mineral Particles Research Articles

Determination of activity/selectivity ratio in physical and chemical adsorption of a reagent

Under discussion is the particle and bubble interaction in froth flotation. Water flow from an interlayer between a particle and a gas bubble under effect of hydrophobic component of wedging pressure is studied. It is assumed for a mineral to be extracted, that electrostatic interaction slightly influences the particle and bubble contingence and the liquid interlayer thinning. For this reason, particular attention is given to the effect exerted by mineral particle surface hydrophobicity on water flow rate from the interlayer. It is found that water flow rate under influence of hydrophobic component of wedging pressure is less than water flow rate under physical adsorption of a reagent. The authors hypothesize that hydrophobization creates areas on the mineral particle surface, where the reagent species active relative to gas–water interface attach in accordance with the polarity equalizing rule. Physically adsorbed reagent species pull out water from the interlayer after the interlayer rupture and, thus, remove the kinetic constraint of the particle–bubble attachment.

Relationships between the biomass and production of bacterio- and phytoplanktonic communities

Quantitative ratios of the biomasses of bacterio- and phytoplankton, interrelation of their production characteristics, and association of the functional characteristics with environmental factors were studied for Lake Khanka, the Yenisei River and the Krasnoyarsk Reservoir. The ratio between the biomasses of bacterioplankton (Bb) and phytoplankton (Bp) in these water bodies was shown to vary within the range exceeding three orders of magnitude. Bacterioplankton biomass was relatively stable and varied from sample to sample by an order of magnitude. In more than 50% of the samples (total sample number, 495), bacterioplankton biomass exceeded that of the phytoplankton. The average Bb/Bp ratios for Lake Khanka, Yenisei River, and Krasnoyarsk Reservoir were 5.1, 2, and 1.4, respectively. Increased Bb/Bp ratios were found to correlate with elevated specific (per unit biomass) phytoplankton production. This finding indicated additional supply of biogenic elements to phytoplankton due to their recycling by bacterial communities. The ratio between bacterioplankton and phytoplankton production for Lake Khanka varied from year to year (0.07 to 0.76). For the Yenisei River and the Krasnoyarsk Reservoir these ratios were on average 0.19 and 0.27, respectively. According to the literature data for other water bodies, bacterial production may reach from 10 to over 100% of the primary production. The equilibrium density of bacterioplankton (maximal density of the population) in Lake Khanka was ~1.5 times higher than in the Yenisei River and the Krasnoyarsk Reservoir due to higher content of suspended mineral matter and associated organo-mineral detritus in the lake. The interaction between dissolved organic compounds sorbed of the surface of mineral particles results in chemical alteration of biochemically stable substrate into compounds which may be assimilated by aquatic micoorganisms.

Effect of biochar and organic fertilizers on C mineralization and macro-aggregate dynamics under different incubation temperatures

Understanding the effects of soil amendments on organic matter dynamics is essential for the sustainable management of soil. Less is known about the effects of biochar in comparison to commonly used organic fertilizers on soil aggregation and organic matter dynamics. Here, we aimed to analyze the effect of biochar, slurry, and manure on carbon (C) mineralization and macro-aggregate formation. Soil material whose macro-aggregates (>250μm) have been carefully crushed was mixed with biochar and/or slurry or manure and incubated at 5°C, 15°C, and 25°C over a period of eight weeks. We determined and modelled the CO2 emissions over the course of the incubation experiment and analyzed the contents of newly formed macro-aggregates, associated C and microbial biomass C after four and eight weeks. Temperature effects on the decomposition intensity were found to be highest for the manure and lowest for the biochar application. CO2 fluxes across treatments and temperatures were mostly satisfactorily described using 1- or 2-pool-models. Macro-aggregate yields were smaller at higher temperatures in the control and biochar (after 4 weeks) as well as manure (after 4 and 8 weeks) treatments, presumably because of a metabolization of binding agents. At 15°C, slurry addition resulted in significantly higher aggregate yields compared to all other treatments, which may be attributed to its more liquid state allowing an easier and more efficient contact with mineral particle surfaces. In combination with slurry, biochar resulted in lower aggregate yields than slurry alone at 15°C. Manure application did not significantly change aggregate yields compared to the control. Correlations between aggregate yields and the microbial biomass or CO2 production point towards a direct interaction of the respective substrates with soil particles to form aggregates followed by decomposition of the amendments and production of microbially derived aggregate binding agents.

Chemical Characterization of PM1 at a Regional Background Site in the Western Mediterranean

From February 2011 to September 2012, PM_1 samples were collected at the regional background station of Mt. Aitana, located near the eastern coast of the Iberian Peninsula at 1558 m a.s.l. Samples were subsequently analyzed to determine the major chemical composition (elemental and organic carbon, secondary inorganic ions and oxalate). The seasonal patterns of the concentrations of PM_1 and its main components and the influence of long-range transport of dust from the Sahara desert were studied in this work. PM_1 was mainly composed of organic matter and ammonium sulfate, while EC and nitrate were minor components. Concentrations ranged from 3.4 μg m^(-3) in winter to 5.8 μg m^(-3) during summer. This seasonal cycle is typical of high mountain sites, which are generally above the planetary boundary layer during winter time. All the analyzed components exhibited the same seasonal pattern except nitrate, which showed minimum values in summer. This is most likely the result of the decomposition of NH_4NO_3 favored by the higher summer temperatures. Due to the close proximity to the African continent, PM_1 levels significantly increased during Saharan dust intrusions. The concentrations of sulfate were 35% higher during dust events since the formation of secondary ammonium sulfate is favored by heterogeneous reactions on the surface of mineral particles.

Tuning Electrical Conductivity of Inorganic Minerals with Carbon Nanomaterials.

Conductive powders based on Barite or calcium carbonate with chemically converted graphene (CCG) were successfully synthesized by adsorption of graphene oxide (GO) or graphene oxide nanoribbons (GONRs) onto the mineral surfaces and subsequent chemical reduction with hydrazine. The efficient adsorption of GO or GONRs on the surface of Barite and calcium carbonate-based mineral particles results in graphene-wrapped hybrid materials that demonstrate a concentration dependent electrical conductivity that increases with the GO or GONR loading.

Gold and silver in a system of sulfide tailings. Part 1: Migration in water flow

Wastes of the ore cyanide process are prone to oxidation and acid leaching that cause mobilization, migration, and precipitation of elements, including noble metals. The issues of waste oxidation, as well as release and transport of oxidation products, are of principal environmental concern and a focus of active geochemical research. We study the behavior of Au and Ag in the natural–industrial system “sulfide wastes–surface/pore waters–particulate matter–bottom sediments” in the presence of different elements (Na, Mg, K, Ca, Al, Fe, Cu, Zn, Se, Ag, Au, Hg, Pb, REE, etс.), at the Novo-Ursk auriferous pyritic deposit (Salair, Kemerovo region, Russia).The wastes include processed primary ore (wastes I) and ore from the gold-bearing weathering profile (wastes II) that store, respectively, 0.5ppm Au, 18ppm Ag and 0.26ppm Au, 13ppm Ag. Gold in wastes I occurs in the native form with Cu and Ag impurities and also Au exist as invisible species in pyrite. In wastes II, gold is adsorbed onto the surfaces of secondary mineral particles (kaolinite, montmorillonite, hydromica, and Fe(III) compounds) while silver is an isomorphic impurity in alunite–jarosite minerals. The oxidation of wastes produces acid mine drainage (AMD) water, with рН=1.9 and high concentrations of sulfate, Fe, Al, Cu, Zn, Pb, As, Se, Te, Hg, Сd, and REE, which flows into the Ur River (a tributary of the Inya).The stream transports gold and silver existing in dissolved+colloidal and particulate forms. Dissolved+colloidal gold and silver have similar distribution patterns with their contents inversely proportional to рН. Dissolved+colloidal gold in the AMD water is more abundant than silver (0.4–1.2ppb Au against 0.1–0.3ppb Ag). Gold changes from the dissolved+colloidal (in AMD) to particulate (till 0.03ppb) forms and precipitates in progressively larger amounts with distance from the tailings. Silver in most of the analyzed natural and tailings-impacted waters exists as suspended particles (to 1ppb). The concentrations of gold and silver are the highest (1.8–2.1ppb Au and 4.5–5.7ppb Ag) in peat pore waters within the geochemical trains of the tailings, apparently as a result of re-precipitation on organic barriers.

Influence of Nonswelling Clay Minerals (Illite, Kaolinite, and Chlorite) on Nonaqueous Solvent Extraction of Bitumen

Artificial mixtures of bitumen with three natural clay standards, dominated by illite, kaolinite, and chlorite, were reacted for several days and washed three times each with cyclohexane to remove bitumen from the clays. The main goal was to determine and better understand the effect of nonswelling clay minerals (illite, kaolinite, and chlorite) on nonaqueous solvent bitumen extraction. The experimental results showed that the total amount of residual cyclohexane insoluble organic carbon (CIOC) measured for clay–bitumen mixtures after nonaqueous solvent bitumen removal is a function of intrinsic resistance of high molecular weight (MW) organic compounds to cyclohexane extraction and the nature of nonswelling clays. The intrinsic resistance of high MW organic compounds to cyclohexane extraction accounted for 42–80% of the total CIOC content. The nonswelling clays retained from 20 to 58% of CIOC of the total CIOC content primarily on the external surfaces (basal planes and edges) of clay mineral particles i...

Impact of Sodium and Sulfur Species on Agglomeration and Defluidization during Spouted Bed Gasification of South Australian Lignite

Transformations of inorganic elements during steam gasification of a high-sodium, high-sulfur lignite were investigated in a 77 mm i.d. spouted bed reactor. The role of sodium and sulfur in agglomeration and defluidization of the bed material is assessed by analysis of inorganics in the bed char, in cyclone dust, in any agglomerates formed, and in deposits formed at the gas inlet to the reactor. It was found that a sodium disilicate-quartz eutectic was the key species in causing stickiness of the surface of mineral particles within the coal. The present data indicate that sodium and silica from the coal are reacting to form sodium silicate species, which forms the “glue” causing solid ash particles to cohere, initiating particle growth and agglomeration. This finding agrees with a fundamental study conducted by other authors. Sodium–calcium–sulfur eutectics, which have been found by other authors to cause agglomeration for similar coals under combustion conditions in a fluidized bed, were only found to form near the steam–air inlet to the reactor and thus do not play a significant part in agglomerate chemistry under the reducing conditions which exist throughout the majority of the bed under gasification conditions.

Interaction of humic acids with soil minerals: adsorption and surface aggregation induced by Ca2+

Environmental context Humic acids, important components of natural organic matter in soils, sediments and aquatic media, can interact with the surface of minerals affecting key environmental processes. In the presence of calcium, humic acids can also interact among themselves leading to molecular aggregates. We demonstrate that a solid mineral surface facilitates the formation of humic acid aggregates, and thus surface aggregation occurs under conditions where normal aggregation in solution does not occur. Abstract Humic acids (HAs) interact with the surface of mineral particles leading to the formation of clay–humic complexes that affect the transport of nutrients and contaminants in the environment, soil structure, soil erosion and carbon sequestration by soils. The interaction is influenced by the presence of multivalent ions, such as Ca2+, which enhances the uptake of HAs by the particles. This article reports the effects of Ca2+ on the interaction between a HA and a soil clay fraction, both obtained from the same soil sample. The study was performed by using zeta potential measurements, HA adsorption isotherms, Ca2+ adsorption isotherms and microscopy. The results show that at low HA concentrations and low Ca2+ concentrations HA adsorption takes place, but that at high concentrations surface aggregation and precipitation also takes place, a process that is seldom reported or analysed in the literature. HA adsorption isotherms only give the overall HA uptake by the solid but they do not allow differentiation of HA adsorption from surface aggregation. However, HA adsorption v. Ca2+ concentration plots and Ca2+ adsorption isotherms at different HA concentrations can distinguish these two processes quite clearly. In addition, surface aggregation could be undoubtedly observed with optical microscopy. Surface aggregation starts to take place at a 0.7mM Ca2+ concentration, which is lower than the Ca2+ concentration needed to start HA aggregation in solution. This indicates that the surface of soil minerals acts as a nucleation centre for HA aggregation.

Preparation of copper oxide in smectites

Copper oxide nanoparticles were prepared in the interlayer spaces of sodium- and cetyltrimethylammonium–smectites by a titration of an aqueous solution of copper nitrate at 70°C in the presence of dispersed smectites. The resulting hybrids were characterized by powder XRD, SEM, TEM, TG-DTA, as well as FT-IR and UV–visible spectroscopies. A massive blue shift (from 490nm to 232–478nm) of the UV–visible absorption observed for the hybrids confirmed the formation of nanometer-sized copper oxide (3–7nm) in the interlayer spaces. A small amount of larger CuO particle with the size of around 0.6–2.9μm formed at the external surface of clay mineral particles. The nature of the broad absorption band (at around 490nm) of pure copper oxide and the hybrids with high copper oxide loading was attributed to the overlapping of the Cu2+ to O2− charge transfer as well as d–d transition of copper oxide. The interactions with smectites played a role in stabilizing and protecting the formed copper oxide nanoparticles.

Soils of wet valleys in the Larsemann Hills and Vestfold Hills oases (Princess Elizabeth Land, East Antarctica)

The properties and spatial distribution of soils and soil-like bodies in valleys of the coastal Larsemann Hills and Vestfold Hills oases—poorly investigated in terms of the soil areas of East Antarctica—are discussed. In contrast to Dry Valleys—large continental oases of Western Antarctica—the studied territory is characterized by the presence of temporarily waterlogged sites in the valleys. It is argued that the deficit of water rather than the low temperature is the major limiting factor for the development of living organisms and the pedogenesis on loose substrates. The moisture gradients in the surface soil horizons explain the spatial distribution of the different soils and biotic complexes within the studied valleys. Despite the permanent water-logging of the deep suprapermafrost horizons of most of the soils in the valleys, no gley features have been identified in them. The soils of the wet valleys in the Larsemann Hills oasis do not contain carbonates. They have a slightly acid or neutral reaction. The organic carbon and nitrogen contents are mainly controlled by the amount of living and dead biomass rather than by the humic substances proper. The larger part of the biomass is concentrated inside the mineral soil matrix rather than on the soil surface. The stresses caused by surface drying, strong winds, and ultraviolet radiation prevent the development of organisms on the surface of the soil and necessitate the search for shelter within the soil fine earth material (endoedaphic niche) or under the gravelly pavement (hypolithic niche). In the absence of higher plants, humified products of their decomposition, and rainwater that can wash the soil profile and upon the low content of silt and clay particles in the soil material, “classical” soil horizons are not developed. The most distinct (and, often, the only diagnosed) products of pedogenesis in these soils are represented by organomineral films on the surface of mineral particles.

Particle morphological and roughness controls on mineral surface charge development

Effects of mineral particle morphology and roughness on potential determining ion (p.d.i.; H+, OH−) loadings achieved at synthetic lepidocrocite (γ-FeOOH) surfaces were predominantly investigated by potentiometry and thermodynamic modeling. Nanosized rod- (RL) and lath-shaped (LL) particles exhibiting different proportions of the same predominant crystallographic faces acquired largely comparable pH, ionic strength and counterion (NaCl, NaClO4) dependencies on p.d.i. loadings. These results supported previous claims that faces ideally containing proton silent sites only, are likely populated by additional proton active sites. This concept was supported further by results of roughened LL-like particles (LLR) also showing highly congruent pH-, ionic strength- and composition-dependent p.d.i. loadings with those of LL and RL. These loadings thereby correspond to maximal levels allowed by net attractive and repulsive forces at each solution composition, irrespective of particle morphology. Contrasting equilibration times required to achieve these loadings revealed considerably slower exchange of p.d.i. and electrolyte ions near the point of zero charge in the rough LLR than in the more idealized LL and RL particles.Thermodynamic modeling was used to test various concepts accounting for these results. The model made use of a novel framework capable of isolating electrostatic contributions from different faces, and of accounting for ion-specific double-layer properties within a single crystallographic face. These efforts made use of capacitance values for each electrolyte ions within the framework of a recently developed Variable Capacitance Model. Attempts at modeling all three particle types were used to suggest that the (010) face contains ∼0.9sitenm−2 of proton active sites, a value notably constrained by recently published Na+, Cl−, and ClO4− loadings derived by cryogenic X-ray photoelectron spectroscopy. The model presented in this work thus provides a means to predict p.d.i. loadings on multifaceted mineral particle surfaces, and can therefore be used to constrain further our understanding of mineral/water interface reactivity.

Biogeochemical Interface Formation: Wettability Affected by Organic Matter Sorption and Microbial Activity

Batch incubation and column percolation experiments with dissolved organic matter solution at different pH values were performed to investigate the effect of organic matter sorption and microbial activity on the wettability of clean quartz sand particles. Sodium azide was used as a biocide to control microbial activity. Changes in wettability were evaluated by contact angle measurements. Wettability of the quartz sand was found to significantly decrease after sorption of organic matter. An adsorbed C content of <0.1 g C kg−1 turned out to be effective in increasing the contact angle from initially 30 to >70°. Results of the percolation experiments revealed that the change in contact angle was depth dependent, with the greatest increase in the upper part of the columns. The low C/N ratio (<10) of the organic matter adsorbed in the upper part of the sand columns percolated without biocide addition suggested that the depth dependency was caused not only by sorption of organic matter but also was affected by microbial activity. This finding was supported by an increasing contact angle for sand columns percolated with a solution close to neutral pH (6.7), where more favorable living conditions for bacteria could be assumed. We also observed a trend of a linear inverse relationship between C/N ratio and contact angle, i.e., increasing contact angle with decreasing C/N ratio. Overall, the results indicated that the formation of biogeochemical interfaces can strongly change the original wetting properties of mineral particle surfaces.

Influence of Bacteria <i>Pseudomonas fluorescens</i> on the Properties of Latvian Clay

Wide varieties of bacteria are able to produce extracellular polymeric substances (EPS) which are mostly composed of polysaccharides. It is suggested that EPS substances can alter certain clay soil properties due to their ability to adhere to the surface of mineral particles. Most common used microorganisms by the researchers for this purpose are of either genus Bacillus or genus Pseudomonas. In this study growth of bacteria P. fluorescens AM PS11 culture in locally obtained clay is studied for the purpose of establishing their influence on rheological properties of clay. An attempt to evaluate it has been made using FT-IR and XRD. Change in plasticity of clay using Atterberg limits method and coefficient of drying sensitivity has also been determined.

Synthesis and study of phospate-polyalkyleneoxide flotation reagent for oxidized minerals

Polyalkylene oxidephosphates were obtained by phosphorylation of polyethylene oxide and polypropyleneoxide of different molecular weight. Evaluation of flotation activity in experiments on the extraction of tungsten oxide from wolf ramite pulp showed that the introduction of oxygen donor atoms into phosphate group substituent, responsible for hydrophobization of the surface of mineral particles, increase the degree of the heavy metal extraction.

Study of adsorptive behaviours of polynaphthalene sulfonate superplasticiser on 3CaO·3Al2O3·CaSO4 mineral

Calcium sulfoaluminate (3CaO·3Al2O3·CaSO4, C4A3S¯) was synthesised with pure chemical reagents. The adsorption amounts of polynaphthalene sulfonate superplasticiser (NSF) on the surface of C4A3S¯ mineral and the mineral mixture (C4A3S¯+Ca(OH)2+CaSO4·2H2O) were detected by ultraviolet–visible absorption spectrometry. The adsorptive behaviours of NSF on the surface of mineral particles in the hydration system were studied. The results showed that the adsorption amount of NSF on C4A3S¯ mineral and the mineral mixture increased with higher initial concentration, the adsorption amount and the maximum adsorption amount increased with prolonged hydration time, and the adsorption amount and maximum adsorption amount of NSF on the mineral mixture were more than those on C4A3S¯ mineral in the hydration system within the same hydration time.

Production of heavy minerals concentrate and bitumen from oil sands froth treatment tailings

AbstractIn producing valuable heavy minerals, including zircon and those bearing titanium dioxide, into a heavy minerals concentrate (HMC), the key technical challenges involve bitumen removal from mineral particle surfaces, rejection of fine gangue and recovery of residual solvent. (Organics and fines contamination severely sours downstream heavy minerals production performance). This is accomplished in a manner that is both conducive and integral with oil sands current bitumen production and processing operations. The Company's research and development efforts are based on sophisticated variations of common unit operations, including flotation, solvent extraction and vapour‐phase stripping. Experimentation has indicated optimal design parameters for these unit operations. A large‐scale physical demonstration was completed with performance that has met or exceeded expectations and, after several months of operation, commercial benefits arising from these novel processes have largely been confirmed and validated. Clean HMC with attractive mineralogy is produced containing residual bitumen values sufficiently low to affect high downstream recoveries of zircon (and titania), while producing coker‐feed quality bitumen.

Multi-scale method of Nano(Micro)-CT study on microscopic pore structure of tight sandstone of Yanchang Formation, Ordos Basin

Abstract Multi-scale (nano-to-micro) three-dimensional CT imaging was used to characterize the distribution and texture of micro-scale pore throats in tight sandstone reservoirs of the Triassic Yanchang Formation, Ordos Basin. First, the low-resolution Micro-CT was used to reflect the micro-pore texture of the core column with a diameter of 2.54 cm. Then, some samples with a diameter of 65 μm was derived from different areas according the different characteristics of micro-pore texture of the core scanned by low-resolution Micro-CT and scanned by high-resolution Nano-CT. Thus, a three-dimensional texture model of nano-scale micro-pores was reestablished and the permebility and porosity data of the sample could be obtained. On a micrometer scale, the size of the micro-pores varies, and their diameters range from 5.4 to 26.0 μm. The micro-pores are isolated, locally in the shape of a band. On a nanometer scale, the quantity of nanoscale micropores increases, the diameter of which ranges from 0.4 to 1.5 μm. The pore throats are arranged in the shape of tube and ball inside or on the surface of mineral particles(crystals). The ball-shaped micropores in nanoscale, often isolated in the three-dimensional space, show the poor connectivity and consequently act as the reservoir space. By contrast, the tube-shaped micropores in nanoscale show certain connectivity with micro-scale tube-shaped micropores and adjacent isolated ball-shaped micropores in nanoscale. Therefore, these tube-shaped micropores in nanoscale serve as throats and pores. Based on the calcution, the permeability of the samples is 0.843×10 −3 μm 2 and porosity is 10%.

Decomposition of clay minerals in model experiments and in soils: Possible mechanisms, rates, and diagnostics (analysis of literature)

The analysis of model experiments on the dissolution of clay minerals showed that, beginning from a certain moment, this process reaches a steady state and proceeds at a constant rate. The minimum dissolution rate was observed in a neutral environment, where this value varied in the range from n × 10−14-n × 10−12 mol/(m2 s). Under acidic and alkaline conditions, this value increased to n × 10−12 or n × 10−10 mol/(m2s) for most clay minerals. The first stage of the dissolution mechanism involved the formation of protonated (in an acidic environment) and deprotonated (in an alkaline environment) complexes, which destabilized and polarized metal-oxygen (or metal-hydroxyl) bonds in the crystal lattice. At the second stage, the rupture of Si-O and Al-O bonds and the release of these components into the solution occurred at a specific concentration of these complexes, and this stage largely controlled the dissolution rate of the mineral. The presence of organic ligands forming mononuclear polydentate complexes on the surface of the mineral particles at the same solution pH increased the dissolution rate of the minerals by several times and sometimes by an order of magnitude proportionally to the concentration of these complexes on the surface of the particles. It was found that the dissolution rates of kaolinite, illite, and smectite in the podzolic horizon of loamy podzolic soil calculated from the losses of clay minerals in the soil profile with consideration for the soil age exceeded the corresponding values obtained in model laboratory experiments at the same pH values by several orders of magnitude. The revealed differences could be related to the long-term functioning of biota in native soils and the existing uncertainties in the assessment of the active surface of mineral particles.

Phosphate desorption from the surface of soil mineral particles by a phosphate-solubilizing fungus

High phosphate (Pi) sorption in soils is a serious limiting factor for plant productivity and Pi fertilization efficiency, particularly in highly weathered and volcanic ash soils. In these soils, the sorbed Pi is so strongly held on the surfaces of reactive minerals that it is not available for plant root uptake. The use of phosphate-solubilizing microorganisms (PSM) capable of Pi desorption seems to be a complementary alternative in the management of these soils. The aim of this study was to evaluate the effectiveness of the soil fungus Mortierella sp., a known PSM, to desorb Pi from four soil minerals differing in their Pi sorption capacity. The fungus was effective in desorbing Pi from all tested minerals except from allophane, and its desorption depended on the production of oxalic acid. The effectiveness of the fungus to desorb Pi was ranked as montmorillonite > kaolinite > goethite > allophane. The quantity of desorbed Pi increased by increasing the amount of sorbed Pi. The Pi sorption capacity expressed as P0.2 value (amount of P required to increase a solution P concentration up to 0.2 mg L−1) was a good indicator of the effectiveness of Mortierella sp. to desorb Pi from soil minerals.