“…That group includes those isotherms where no competitive action between the adsorbate and solvent occurs. The same form of isotherms was achieved by those authors, who studied phosphorus adsorption processes on goethite [13,15] and on other iron-containing adsorbents, e.g., the alginate/Fe 3+ hydrogel beads [33], lignocellulose [43], wood biomass partially impregnated with carboxylmethylcellulose, and FeCl 3 [44,45] or surfactant-modified natural zeolite [46]. As a result of studies on adsorption of phosphorus on a mix of iron oxide and gypsum, an S-type adsorption isotherm was obtained, characteristic for arrangements where the solvent is strongly adsorbed.…”
The basic process to reduce the phosphate ions in aquatic environments is to move the phosphorus circulation processes on the water–sediment phase boundary towards depositing it in the solid phase through chemical precipitation or adsorption. Modern technologies for removal of phosphorus can be based on cheap and environmentally friendly natural polysaccharides modified with multivalent metals. In this study alginate/goethite hydrogel composite has been investigated for phosphate uptake from aqueous solutions. The composite was produced by a cross-linking reaction between sodium alginate and calcium chloride in six configurations of suspensions, which differed in goethite content. In all cases, spherical and durable capsules of alginate/goethite composite were produced. In laboratory tests, mechanical stability of the capsules at various temperatures and the coexisting ions of lake water were tested. Chemical composition of the aquatic environment had a strong influence on their mechanical stability. Static batch adsorption of phosphate studies were carried out for two adsorbents: goethite and alginate/goethite composite. The goethite gelation resulted in almost double growth of sorption capacity in the case of adsorption from deionized water and, on average, a 50% growth in adsorption from the environmental water compared to raw goethite. The alginate/goethite adsorbent removed phosphate in a wide pH spectrum—from 4 to 10. Results suggest that the proposed adsorbent has potential for the removal of phosphate from contaminated water.
“…That group includes those isotherms where no competitive action between the adsorbate and solvent occurs. The same form of isotherms was achieved by those authors, who studied phosphorus adsorption processes on goethite [13,15] and on other iron-containing adsorbents, e.g., the alginate/Fe 3+ hydrogel beads [33], lignocellulose [43], wood biomass partially impregnated with carboxylmethylcellulose, and FeCl 3 [44,45] or surfactant-modified natural zeolite [46]. As a result of studies on adsorption of phosphorus on a mix of iron oxide and gypsum, an S-type adsorption isotherm was obtained, characteristic for arrangements where the solvent is strongly adsorbed.…”
The basic process to reduce the phosphate ions in aquatic environments is to move the phosphorus circulation processes on the water–sediment phase boundary towards depositing it in the solid phase through chemical precipitation or adsorption. Modern technologies for removal of phosphorus can be based on cheap and environmentally friendly natural polysaccharides modified with multivalent metals. In this study alginate/goethite hydrogel composite has been investigated for phosphate uptake from aqueous solutions. The composite was produced by a cross-linking reaction between sodium alginate and calcium chloride in six configurations of suspensions, which differed in goethite content. In all cases, spherical and durable capsules of alginate/goethite composite were produced. In laboratory tests, mechanical stability of the capsules at various temperatures and the coexisting ions of lake water were tested. Chemical composition of the aquatic environment had a strong influence on their mechanical stability. Static batch adsorption of phosphate studies were carried out for two adsorbents: goethite and alginate/goethite composite. The goethite gelation resulted in almost double growth of sorption capacity in the case of adsorption from deionized water and, on average, a 50% growth in adsorption from the environmental water compared to raw goethite. The alginate/goethite adsorbent removed phosphate in a wide pH spectrum—from 4 to 10. Results suggest that the proposed adsorbent has potential for the removal of phosphate from contaminated water.
“…6), characteristic for the arrangements free from competitive interactions between the adsorbent and the solvent. The same form of isotherm was received by authors examining the process of phosphorus adsorption on various adsorbents, e.g., goethite (Chitrakar et al 2006; Nowack and Stone 2006), wood fiber treated with carboxymethyl (Eberhardt et al 2006; Eberhardt and Min 2008), and surfactant-modified natural zeolite (Dionisiou et al 2013). In the course of tests on phosphate adsorption on a mixture of iron oxide and gypsum, an adsorption isotherm class S was obtained, as characteristic for arrangements where the solvent is strongly adsorbed (Bastin et al 1999)Fig.…”
Section: Resultsmentioning
confidence: 85%
“…Because the coagulation and precipitation processes in the natural waters are accompanied by co-precipitation and adsorption processes of different forms of phosphorus (Xiong and Peng 2011), a variety of adsorbents are added to water, for instance, iron oxide in order to increase their rate and to decrease the desorption of phosphorus compounds from the bottom sediments (Geelhoed et al 1997; Zeng and Li 2004; Chitrakar et al 2006). Other widely promoted adsorbents are lanthanum-modified bentonite (Haghseresht et al 2009), natural zeolite (Tian et al 2009; Dionisiou et al 2013; Meng et al 2013), mesoporus silicate material (Zhang et al 2011), composite adsorbents containing two (or more) different metal oxides (Long et al 2011; Li et al 2014), and poly (vinyl alcohol) hydrogel beads with aluminum (Hui et al 2014). Tian et al (2009) recommended adsorption as one of the most effective removal processes for the low concentration of phosphorus.…”
Binding phosphate at participation of alginate/FeCl3 capsules was studied with laboratory experiments. The hydrogel microcapsules were obtained with the dropping-in method, by gelation of sodium alginate water solution by iron (III) chloride solution. Phosphate adsorption characteristics were studied in a static batch system with respect to changes in contact time, initial phosphates concentration, pH of solution, and temperature. After 24 h of the tests, average 87.5% of phosphate ions were removed from the natural water solutions; after 48 h, an equilibrium was reached. The adsorption data were well fit by the Freundlich isotherm model. Parameter k of the isotherms amounted from 43.4 to 104.7, whereas parameter n amounted from 0.362 to 0.476. The course of processes of phosphate adsorption and iron desorption to aquatic phase, as well as changes in pH, suggests that phosphate adsorption is a major mechanism of phosphate removal, whereas simultaneously, but at a much lower degree, a process of precipitation of phosphate by iron (III) ions released from the capsules to the solution takes its place. Parameters calculated in the Freundlich isotherm equation show that by using several times smaller amounts of iron, it is possible to remove similar or bigger amounts of phosphorus than with other adsorbents containing iron. The alginate/FeCl3 adsorbent removes phosphate in a wide pH spectrum—from 4 to 10. Results suggest that the proposed adsorbent has potential in remediation of contaminated waters by phosphate.
“…The isotherms are most commonly found in solute adsorption in aqueous solution and it was indicated that the adsorption occurs due to relatively weak forces, such as van der Waals forces and a low competition from solvent molecules [ 35 ]. The same form of isotherm was received by authors examining the process of phosphate adsorption on various adsorbents, e.g., goethite [ 12 ], wood fiber treated with carboxymethyl [ 18 ] and surfactant-modified natural zeolite [ 36 ].…”
Wastewater is characterized by a high content of phosphate and toxic metals. Many studies have confirmed the sorption affinity of alginate adsorbents for these ions. In this study, the adsorption of phosphate from effluent of sewage sludge on biodegradable alginate matrices cross-linked with Fe3+ ions (Fe_Alg) was investigated. Kinetics and adsorption isotherms were tested in laboratory conditions in deionized water (DW_P) and in the effluent (SW_P), and in the same solutions enriched in toxic metals ions—Cu2+, Cd2+, Pb2+, and Zn2+ (DW_PM and SW_PM). Batch experiments were performed by changing the concentration of phosphate at constant metal concentration. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data for both metals and phosphate. The Freundlich equation provided the best fit with the experimental results of phosphate adsorption from DW_P and DW_PM, while the adsorption from SD_P and SD_PM was better described by the Langmuir equation. For tested systems, the affinity of the Fe_Alg for metal ions was in the following decreasing order: Pb2+ > Cu2+ > Cd2+ > Zn2+ in DW_PM, and Pb2+ > Cu2+ > Cd2+ > Zn2+ in SW_PM. The metals’ enrichment of the DW_P solution increased the affinity of Fe_Alg beads relating to phosphate, while the addition of the metals of the SW_P solution decreased this affinity.
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