title: Fluoride removal from aqueous solution by direct contact membrane distillation: theoretical and experimental studies.
abstract: Direct contact membrane distillation (DCMD) process using polyvinylidene fluoride (PVDF) membrane was used for fluoride removal from aqueous solution. This study has been carried out on heat and mass transfer analyses in DCMD. The dusty-gas model was used to analyze the mass transfer mechanism and to calculate the permeate flux. The heat transfer is analyzed based on energy balance, and the different layers are considered as a series of thermal resistances. Mass transfer analysis showed that the transition Knudsen-molecular diffusion is the dominant mechanism to describe the transport of water vapor through the pores of the PVDF membrane. The most significant operating parameter is the feed temperature. The permeate increases sensitively with feed temperature and velocity, and it shows insignificant change with feed salts concentration. Heat transfer analysis showed the conduction through the matrix of the membrane presents the major part of available energy. The increasing feed temperature leads to increase thermal efficiency (TE) and decrease temperature polarization coefficient (TPC). The experimental results are in good agreement with theoretical values. Therefore, it is suggested to work at high feed temperature, which will benefit both the thermal efficiency and permeate flux. The experimental results proved that DCMD process is able to produce almost fluoride-free water suitable for many beneficial uses.
authors.affiliation: Laboratory of Wastewater Treatment, Center of Researches and Water Technologies, PB 273, 8020, Soliman, Tunisia, ali.boubakri@certe.rnrt.tn.
authors.forename: Ali
authors.initials: A
authors.lastname: Boubakri
authors.forename: Raja
authors.initials: R
authors.lastname: Bouchrit
authors.forename: Amor
authors.initials: A
authors.lastname: Hafiane
authors.forename: Salah Al-Tahar
authors.initials: SA
authors.lastname: Bouguecha
mesh_terms: D057168:Distillation; D005459:Fluorides / Q000032:analysis / Q000302:isolation & purification*; D008567:Membranes, Artificial; D008956:Models, Chemical; D011145:Polyvinyls; D013696:Temperature; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D005465:Fluorocarbon Polymers
chemical_list: D005459:Fluorides; D008567:Membranes, Artificial; D011145:Polyvinyls; D014874:Water Pollutants, Chemical; C024865:polyvinylidene fluoride; D005465:Fluorocarbon Polymers
references.citation: J Hazard Mater. 2009 Sep 15;168(2-3):888-94
references.pmid: 19327886
references.citation: J Hazard Mater. 2013 Oct 15;261:307-15
references.pmid: 23959250
references.citation: J Environ Manage. 2009 Oct;91(1):67-77
references.pmid: 19775804
references.citation: Water Res. 2010 Nov;44(19):5750-60
references.pmid: 20579681
references.citation: Sci Total Environ. 2014 Aug 1;488-489:532-8
references.pmid: 24238810