Abstract
This manuscript presents new method of phosphorus recovery from aqueous solutions in a convenient form of readily-soluble phosphates using chitosan hydrogels. Non-modified chitosan hydrogel granules (CHs) and chitosan hydrogel granules crosslinked with epichlorohydrin (CHs-ECH) served as orthophosphate ion carriers. The developed method was based on cyclic sorption/desorption of orthophosphates, with desorption performed in each cycle to the same solution (the concentrate). The concentrations of orthophosphates obtained in the concentrates depended on, i.a., sorbent type, sorption pH, source solution concentration, and desorption pH. Phosphorus concentrations in the concentrates were even 30 times higher than these in the source solutions. The maximum concentrate concentrations reached 332.0 mg P-PO4/L for CHs and 971.6 mg P-PO4/L for CHs-ECH. The experimental series with CHs-ECH were characterized by higher concentrations of the obtained concentrate, however the concentrates were also more contaminated with Cl− and Na+ ions compared to series with CHs. The high content of chlorine and sodium ions in the concentrates was also favored by the low pH of sorption (pH < 4) and very high pH of desorption (pH > 12) in the cycles. After concentrate evaporation, phosphorus content in the sediment ranged from 17.81 to 19.83% for CHs and from 16.04 to 17.74% for CHs-ECH.
Highlights
MethodsPreparation of non‐crosslinked chitosan hydrogel granules (CHs). 25 g d.m. of chitosan flakes, 925 g of water, and 50 g of acetic acid were added into a beaker (vol 2000 mL) and stirred with a spatula until chitosan dissolved completely
Due to the rapid salination of the concentrate at pH 13 in the successive cycles, higher maximum concentrations of the concentrate were obtained in the experimental series with desorption performed at pH 12
A too long contact time of the sorbent with the desorption solution could result in re-resorption of orthophosphates, that had earlier been released to the solution
Summary
Preparation of non‐crosslinked chitosan hydrogel granules (CHs). 25 g d.m. of chitosan flakes, 925 g of water, and 50 g of acetic acid were added into a beaker (vol 2000 mL) and stirred with a spatula until chitosan dissolved completely. The chitosan hydrogel sorbents were pre-treated by orthophosphate sorption using the N aH2PO4 solution (10 mg P-PO4/L) with pH value optimal for each sorbent (established in point 3.3). After 2 h, samples (10 mL) were collected from each flask to determine the concentration of P-PO4 in desorption solutions. After 0, 5, 10, 15, 20, 30, 45, 60, 90, 120, 150, 180, and 240 min, samples (5 mL) were collected from the flasks to determine P-PO4 concentration in desorption solutions. N aH2PO4 solutions with concentrations of 10/50/100 mg P-PO4/L and an optimal sorption pH (established for each sorbent in point 3.3) were poured into the flasks. After optimal desorption time (established in point 3.6), the sorbent was separated from the desorption solution (concentrate) using laboratory screens. Where k1—constant in the pseudo-first order equation [L/min], k 2—constant in the pseudo-second order equation [L/min], qe—equilibrium amount of sorbed/desorbed phosphorus [mg P-PO4/g]; q—momentary amount of sorbed/desorbed phosphorus [mg P-PO4/g]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
