Removal of Phosphate from Aqueous Solution Using Alginate/Iron (III) Chloride Capsules: a Laboratory Study

Abstract

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.

Adsorption of Phosphates from Aqueous Solutions on Alginate/Goethite Hydrogel Composite

“…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.…”

“…In the case of alginate with modification by Fe 3+ , some adsorbents were produced for purifying water from oxygen anions containing Se 4+ , Cr 6+ , and As 5+ [30,31]. The literature refers to two similar formula obtained for adsorption of phosphate ions from the aquatic phase alginate/zirconium sulfate matrix, which has better sorptive qualities than powdered zirconium sulfate [32] and alginate/Fe 3+ beads [33].…”

Natural vs. Synthetic Phosphate as Efficient Heterogeneous Compounds for Synthesis of Quinoxalines

“…The phenomenon of phosphate adsorption in Scheme 2 presents the creation route of this coordination structure on the surface of NP. Two surface oxygen groups of NP exist in intermediate I and II (shown in Scheme 3), by which the aminic hydrogen (NH) of diamine can form a doubly H-bonded composition to give hydroxyl (see structures 1 and 2, Schemes 2 and 3); subsequently, they are replaced with one oxygen of phosphate group (P 2 O 5 ) of NP [60][61][62]. It is confirmed that gray-to-black-colored particles that appeared on the recycled NP is hematite (Fe 2 O 3 ), which is released from NP during the reaction [63,64].…”

Competitive Interaction of Phosphate with Selected Toxic Metals Ions in the Adsorption from Effluent of Sewage Sludge by Iron/Alginate Beads

“…After chemical modification, it can be converted into adsorbents with anionic sorption capacity. By such modification using Fe(III) or Zr(IV) compounds, adsorbents for purifying water from oxygen anions containing Se(IV), Cr(VI) and As(V) [ 25 , 26 ] or P [ 27 , 28 ] compounds were obtained.…”