Competitive Adsorption Of Phosphate Research Articles

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.

Effect of coexisting ions on adsorptive removal of arsenate by Mg-Fe-(CO3) LDH: multi-component adsorption and ANN-based multivariate modeling

The adsorptive removal of a pollutant from water is significantly affected by the presence of coexisting ions with various concentrations. Here, we have studied adsorption of arsenate [As(V)] by calcined Mg–Fe–(CO3)–LDH in the presence of different cations (Mg2+, Na+, K+, Ca2+, and Fe3+) and anions (CO3 2‒, Cl‒, PO4 3‒, SO4 2‒, and NO3 ‒) with their different concentrations to simulate the field condition. The experimental results indicated that Ca2+, Mg2+ , and Fe3+ have a synergistic effect on removal efficiency of As(V), whereas PO4 3‒ and CO3 2‒ ions have a significant antagonistic impact. Overall, the order of inhibiting effect of coexisting anions on adsorption of As(V) was arrived as NO3 –˂Cl–<SO4 2–<CO3 2 –<PO4 3 –. Among them, competitive adsorption of phosphate with arsenic at different initial phosphate concentrations was found to be responsive to formulate a binary adsorption system. We have also developed a modified non-competitive Langmuir and Langmuir–Freundlich models; however, the modified competitive Langmuir model was arrived to be the most adequate model for this binary system. An Artificial Neural Network based multivariate prediction model was developed, delineating the impact of coexisting ions on the adsorption system. The proposed method may appropriately demonstrate the overall system and exhibited a significantly adequate prediction model with high R2, high F-value, and low error values.

Competitive adsorption of phosphate and dissolved organic carbon on lanthanum modified zeolite

Lanthanum (hydr)oxide-based materials are attractive as highly efficient adsorbents for phosphate removal from both sewage and lake environment. However, dissolved organic carbon (DOC) coexists in the waters and exact information is still lacking on how DOC influence the phosphate adsorption process. In this study, competitive adsorption of phosphate and DOC on lanthanum modified zeolite (LMZ) was investigated using humic acid as the representative. In LMZ, lanthanum hydroxide was shown to be the active ingredient accounting for >98% of the binding sites of both phosphate and DOC. Without competition, the maximum adsorption capacity of phosphate and DOC estimated from the Langmuir isotherm model was 52.25 and 41.32 mg/g, respectively. When coexisted, DOC did not affect the adsorption of phosphate while phosphate reduced the adsorption of DOC by ~40%. In addition, preloading LMZ with DOC had little effect on phosphate adsorption while coating with phosphate substantially lowered DOC adsorption. Furthermore, phosphate can release most of the adsorbed DOC (>60%), while DOC can not replace adsorbed phosphate (<2%). The adsorption kinetics of both phosphate and DOC was best described by the psudo-second-order model (r2 > 0.999). The adsorption of both phosphate and DOC increased with decreasing pH or increasing ionic strength. We proposed that phosphate was competitive than DOC for the ligand exchange sites of singly-coordinated hydroxyls, but DOC can be solely adsorbed onto the uncharged hydroxyls via hydrogen bonding.

Effect of Si/Al Ratio of Allophane on Competitive Adsorption of Phosphate and Oxalate*

Effect of Si/Al Ratio of Allophane on Competitive Adsorption of Phosphate and Oxalate*

Effect of Si/Al Ratio of Allophane on Competitive Adsorption of Phosphate and Oxalate

Effect of Si/Al Ratio of Allophane on Competitive Adsorption of Phosphate and Oxalate

Adsorption of glyphosate on clays and soils from Paraná State: effect of pH and competitive adsorption of phosphate

This work showed that the adsorption of glyphosate (GPS) depends on surface area for clays and amount of clays and CEC for soils. Organic matter (OM) had a secondary role in the adsorption of GPS on soils. The adsorption of GPS on soils from Londrina and Floraí counties and clays (montmorillonite, kaolinite) decreased when pH increased, however, for bentonite clay and soil from Tibagi county was kept constant. For the soils, the competitive adsorption between GPS and phosphate showed that displace of GPS by phosphate was related to the amount of clays, CEC and pH. GPS was not easily displaced by phosphate on the clays. The FT-IR spectra of the soils and clays showed that soil from Londrina resembled kaolinite. Thus, this could explain the results of adsorption of GPS and the competitive adsorption between GPS and phosphate.

Adsorption of 2,4‐Dichlorophenoxyacetic Acid by an Andosol

To identify the important soil components involved in 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption on Andosols, 2,4-D adsorption on a surface horizon of an Andosol was compared with that on hydrogen peroxide (H2O2)-treated (soil organic matter [SOM] was removed), acid-oxalate (OX)-treated (active metal hydroxides and SOM were removed), and dithionite-citrate-bicarbonate (DCB)-treated (free and active metal [hydr]oxides and SOM were removed) soil samples at equilibrium pHs ranging from 4 to 8. Although the untreated soil contained a large amount of organic C (71.9 g kg-1), removal of SOM had little effect on 2,4-D adsorption. Active surface hydroxyls, which were attached to the active and free metal (hydr)oxides and metal SOM complexes, were identified as the most important soil functional group for 2,4-D adsorption. The dominant mechanism of the 2,4-D adsorption was a ligand exchange reaction in which the carboxylic group of 2,4-D displaced the active surface hydroxyl associated with metals and formed a strong coordination bond between the 2,4-D molecule and soil solid phase. The ligand exchange reaction reasonably accounted for the selective adsorption of 2,4-D over Cl-, competitive adsorption of phosphate over 2,4-D, reduction in plant-growth-inhibitory activity of soil-adsorbed 2,4-D, and the high 2,4-D adsorption ability of Andosols. Although a humic acid purified from the soil did not adsorb 2,4-D, the presence of the humic acid increased 2,4-D adsorption on Al and Fe, probably by inhibiting the hydrolysis and polymerization of Al and Fe resulting in the preservation of available adsorption sites on these metals. The adsorption behavior of 2,4-D on soils could be a good index for predicting the adsorption behavior of other organic acids in soils.

Competitive adsorption of phosphate and phosphonates onto goethite

Phosphate and phosphonates are both strongly adsorbed onto mineral surfaces and their removal during wastewater treatment is mainly due to adsorptive processes. We have conducted experiments to study the mutual influence of phosphate and six different phosphonates on each other in buffered medium at pH 7.2. We have used phosphonates having one to five phosphonic acid groups (HMP, IDMP, HEDP, NTMP, EDTMP and DTPMP). The presence of phosphonates suppressed the adsorption of phosphate. The monophosphonate HMP had the smallest and the polyphosphonates the largest effect on phosphate adsorption. The presence of phosphate lowered phosphonate adsorption. The competition in the multicomponent system can reasonably well be predicted using a surface complexation model developed for single component systems. The competitive model only failed in systems containing the polyphosphonate DTPMP. With this approach we can predict the behavior of both compounds during wastewater treatment. The calculations show that phosphonates have a small effect on phosphate adsorption at the actual concentrations in observed wastewater. Adsorption of low concentrations of phosphonates was calculated to be significantly reduced by phosphate concentrations as observed in wastewater.

Individual and competitive adsorption of phosphate and arsenate on goethite in artificial seawater

Phosphate and arsenate adsorption on goethite was studied in single batch experiments at 25 °C upon the addition of Ca 2+, Mg 2+ and SO 4 2− to a 0.7 M NaCl solution at their respective seawater concentrations. Phosphate adsorption increases slightly in the presence of Mg 2+ and Ca 2+ and decreases at low pH upon the addition of SO 4 2−. The enhanced adsorption may result from the formation of ternary surface complexes. In contrast, arsenate adsorption is not affected by the addition of Mg 2+ or Ca 2+ to the 0.7 M NaCl solution. Similarly, phosphate adsorption in seawater is enhanced at neutral pH relative to 0.7 M NaCl, whereas arsenate adsorption is identical in both solutions except for a decrease at low pH in seawater. An equilibrium model derived by combining interaction parameters obtained from the single adsorbate subsystems predicts the phosphate and arsenate adsorption behaviours in the PO 4–SO 4–goethite and AsO 4–Ca–goethite systems very well but fails to accurately reproduce the adsorption data in the PO 4–Ca–goethite, PO 4–Mg–goethite, PO 4–seawater–goethite, AsO 4–Mg–goethite and AsO 4–seawater–goethite systems. The inclusion of ternary surface complexes in the latter systems improves model fits significantly at high pH. Experimental investigations of phosphate and arsenate competitive adsorption in seawater were also carried out. The fraction of phosphate adsorbed in the competitive experiments in seawater is identical to the results obtained in the 0.7 M NaCl solution, whereas arsenate adsorption is greater in seawater at pH>7. The difference in the extent of arsenate adsorption in both solutions is proportional to the initial amount of phosphate in solution. In competitive experiments in seawater, phosphate adsorption is underpredicted at pH<6.5, whereas arsenate adsorption is reproduced well using the constant capacitance model (CCM) with the inclusion of ternary surface complexes.

Competitive adsorption of phosphate and carboxylate with natural organic matter on hydrous iron oxides as investigated by chemical force microscopy

Abstract The behaviour of phosphate and natural organic matter (NOM) in soils and aqueous media is strongly influenced by their association with surfaces of colloidal mineral oxide and oxyhydroxide particles of iron. Here we investigate the interaction of atomic force microscope (AFM) tips terminated with bis(11-thioundecanoic)phosphate and 16-thiohexadecanoic acid as a function of pH in the context of competitive phosphate–organic matter adsorption interactions at the surface of hydrous iron oxide colloids. Experiments were carried out on unmodified colloids as well as colloids coated with gallic acid, tannic acid or peat-derived humic material. The colloids were also examined by infrared spectroscopy (IR) and zeta potentiometry. Force titrations on a gallic acid control surface revealed that the main mode of interaction of this compound with the tips was hydrogen bonding. A strong interaction in the pH range 4–8 observed for the PO2H probe on the unmodified iron (hydroxy)oxide was attributed to a specific adsorption reaction with an A-type FeOH surface site. The CO2H tip displayed a strong but less specific interaction that extended over the pH range 4–10. Force titrations of probes against colloids post-precipitated with gallic acid, tannic acid or peat-derived humic material were significantly different than for the unmodified surfaces. Surface-bound organic molecules reduced the specific mid pH range interactions and gave rise to two new force titration features with maxima about pH 4 and 8, which were assigned to H-bonding between the probes and benzoic and phenolic groups of surface-bound organic acids, respectively.

Competitive adsorption of phosphate and arsenate on goethite.

The competitive adsorption of phosphate and arsenate on goethite was investigated to better understand the bonding mechanisms for the two ions. The anions were added both simultaneously and sequentially. When added simultaneously, the two ions were adsorbed about equally, with the total surface coverage being slightly greater than for either ion alone. When added sequentially, the extent of exchange for the first ion depended on the equilibration time before the second ion was introduced--the longer the equilibration time the greater the exchange. There is a nonexchangeable fraction for both ions that is approximately equal to the initially adsorbed amount of each ion. The results suggest a two-phase reaction on the surface, with the first phase being a rapid surface complex formation on the goethite surface, followed by the slower buildup of a surface precipitate on the adsorbed layer. The exchangeable ions are in the surface precipitate. These results are incompatible with a surface complexation model (SCM) for anion adsorption on geothite and indicate that the actual reactions are more complicated than the reaction assumed in a SCM.

Competition in Adsorption between Phosphate and Oxalate on an Aluminum Hydroxide Montmorillonite Complex

AbstractA study was conducted to provide information on phosphate and oxalate sorption on an Al(OH)x‐montmorillonite (chlorite‐like) complex under changing conditions of pH, total solution ligand concentrations, and order of anion addition. The competitive adsorption of phosphate and oxalate on a chlorite‐like complex (3.3 mol Al kg−1 montmorillonite) was influenced by pH (5.0–9.0), order of anion addition, and initial oxalate/phosphate molar ratio (Ri). In systems containing a constant amount of phosphate (500 or 400 mmol kg−1) and increasing quantities of oxalate (Ri from 0.5 to 3.34), more phosphate than oxalate was adsorbed even when the initial concentration of oxalate was much higher than that of phosphate. Of the sites on the clay surface that were available for adsorption by both anions, 51 to 79% were occupied by phosphate at Ri = 3.34 in the range of pH studied. Minimum reduction in phosphate adsorption occurred when phosphate was added to the clay mineral before oxalate, whereas maximum reduction occurred when oxalate was introduced before phosphate. The efficiency of oxalate in inhibiting phosphate adsorption was stronger at pH 5.0 than at pH 7.0 or 9.0. At pH 5.0, by increasing Ri from 0.5 to 3.34, phosphate sorption decreased from 20 to 44% when OX was added before phosphate. Many sites of the clay mineral were highly specific for phosphate, whereas some others, common to both the anions, had a higher affinity for phosphate than for oxalate. However, some sites were specific for oxalate anions.

Competitive Adsorption of Phosphate and Oxalate by Aluminum Oxides

AbstractThe aim of this work was to study: (i) the competitive adsorption of phosphate (P) and oxalate (OX) anions on an Al oxide as influenced by pH and order of anion addition; and (ii) the adsorption of P on and the desorption of OX from an Al precipitation product [Al(OH)x‐OX] formed in the presence of OX ions. The amount of P adsorbed on Al oxide in the absence of OX decreased with increasing pH. In the absence of P, OX adsorption exhibited a broad maximum between pH 5.0 and 7.0, but rapidly decreased at a pH &lt;5.0 or &gt;7.0. The order of anion addition strongly influenced the adsorption of both P and OX. Maximum reduction in P adsorption occurred when OX was introduced before P, whereas reduction was negligible when P was added before OX. The efficiency of OX in reducing P adsorption was relatively high at acidic pH values, but it was poor at a pH &gt;7.0. The presence of P strongly depressed OX adsorption when P was added before OX or when the anions were added together. The efficiency of P in reducing OX adsorption increased with increasing pH. Finally, the ability of P in replacing OX ions from Al(OH)x‐OX was poor at pH values &lt;7.0, but increased in alkaline environments with increasing pH. The data thus reveal that OX ions compete strongly with P for adsorption sites of Al oxides when they are added before the inorganic ions or are coprecipitated with Al in Al precipitation products, and mainly at acidic or neutral pH values.

Competitive adsorption of phosphate on goethite in marine electrolytes

Competitive adsorption of phosphate on goethite in marine electrolytes

Competitive Adsorption of Phosphate with Malate and Oxalate by Tropical Soils

AbstractA study about the competition between organic anions (oxalate and malate)—currently present in the rhizosphere and phosphate for adsorption sites in tropical soils—indicate that in the presence of organic anions, phosphate adsorption by soils is reduced. The extent of such reduction is dependent on the way in which either phosphate or the organic anion are added to the soil. The organic oxyanions studied are more rapidly adsorbed to the soil surface than the phosphate; consequently those anions, when existing in the rhizosphere, can improve the phosphate status of soil.

Competitive Adsorption of Phosphate with Polygalacturonate and other Organic Anions on Kaolinite and Oxide Surfaces

SOME plants are known to remove phosphate readily from soils low in phosphate. It is likely that root excretions and microorganisms greatly modify the chemical environment in the rhizosphere and this may result in the more ready displacement of the adsorbed phosphate from soil colloids. Organic compounds found in the root exudates of several plants, reviewed by Rovira1, include many organic acids known to form strong complexes with metal ions. Examination of the root–soil interface under the electron microscope has also revealed a slimy gel between the root and the soil colloidal particles2,3, which has been called “mucigel” and is considered to consist of pectic substances, chiefly partially methylated polygalacturonic acids.