Removal of phosphate by Donnan dialysis coupled with adsorption onto calcium alginate beads

Abstract

In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.

Transport and Electrochemical Characteristics of CJMCED Homogeneous Cation Exchange Membranes in Sodium Chloride, Calcium Chloride, and Sodium Sulfate Solutions

“…Concentration dependences of the specific electrical conductivity of CMX membrane (κ * ) upon the specific electrical conductivity of NaCl solutions (a) and lgκ * vs lgκ (b) coordinates, Figure S3. Schematic of the unit for measuring the diffusion permeability of membranes: (1) two-compartment cell, (2) membrane under study, (3,4) flow-through compartments of cell 1, (5) tank with distilled water, (6) tank with an electrolyte solution of the set concentration, (7) pumps, (8) conductometer, (9) immersion conductometric cell, (10-13) connecting hoses, ( 14) pH meter, and (15) combined glass electrode for pH measurements, Figure S4. Schematic design of the set-up used for determining mass transfer and electrochemical characteristics of the CEM membranes forming the desalination compartment.…”

“…Schematic design of the set-up used for determining mass transfer and electrochemical characteristics of the CEM membranes forming the desalination compartment. The set up includes: an intermediate feed tank (1); an additional tank (2) for maintaining a constant pH; valves (3,4); Luggin capillaries (5) connected with measuring Ag/AgCl electrodes (6); platinum polarizing electrodes (7); an electrochemical complex (an Autolab PGSTAT-100) (8); a flow cell (9) with an immersed combined electrode for pH measurement; a pH meter (10) connected to a computer; a combined electrode for pH measurement (11) connected to a pH meter; a conductivity cell (12) connected to a conductometer; a device (13) for maintaining a constant pH in the solution circulating through tank (2); CEM * are the cation-exchange (CMX, CJMC-5, CJMC-3) membranes under study; CEM and AEM are the auxiliary membranes. The dotted lines schematically show the electrolyte concentration profiles in the cell compartments: 15-compartment with an enriched diffusion layer next to the membrane under study, 16-desalination compartment with a depleted diffusion layer next to the membrane under study, Table S1: Some characteristics (at 25 • C) of ions included in the studied solutions.…”

“…Recently, ion-exchange membranes (IEMs) have been widely used in capacitive deionization [ 1 ], electrolysis [ 2 ], Donnan [ 3 ] and neutralization dialysis [ 4 ], fuel cells [ 5 , 6 ], and bioelectrochemical systems [ 7 ]. They are utilized for extracting valuable components, such as ammonia, along with producing electricity [ 8 ], and in other applications.…”

“…Membrane equilibrated with 0.02 M NaCl solution;2 Membrane equilibrated with 0.5 M NaCl solution;3 The data were provided by the manufacturer.…”

Response Surface Methodology for Boron Removal by Donnan Dialysis: Doehlert Experimental Design

“…This process is easy to handle and only requires a few chemicals and low pumping energy. Donnan dialysis is widely used to recover or concentrate [ 20 , 21 , 22 ] and eliminate various ions such as nitrates [ 23 ], nitrates and nitrites simultaneously [ 24 ], fluorides [ 25 , 26 , 27 ], chromium [ 28 , 29 ], phosphates [ 30 ] and boron [ 18 , 19 ].…”