The effects of pH and calcium on the diffusion coefficient of humic acid

Wang, Yingge; Combe, Corine; Clark, Mark M.

doi:10.1016/s0376-7388(00)00555-x

Cited by 110 publications

(63 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result, the molecular volume decreases at low solution pH and high ionic strength, and the adsorption process is facilitated due to greater access to porous media in which HA molecules can penetrate and be retained, which will increase the adsorption of HA onto the solid surfaces of particles and increase the R values. Our results were also supported by the findings of [1] and by the HA molecular shape changes due to solution pH and ionic strength changes indicated by [18] and [35].…”

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportsupporting

confidence: 88%

“…This, in turn, will significantly influence diffusivity [12], which will ultimately affect the dispersion coefficients. This is evidenced by the results of [11] and [35] who found that the larger dispersion coefficients of HA at relatively low solution pH and large ionic strength conditions are associated with increased diffusivity.…”

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportmentioning

confidence: 90%

“…It has been suggested that HA may exist as a spherical structure at lower pH and higher ionic strengths and as linear or stretched structures at higher pH and lower ionic strengths [35]. Ghosh and Schnitzer [18] also concluded that the shapes of HA molecules could be transformed from large, flexible, linear shapes at high pH and low ionic strengths to small, rigid, spherical shapes at low pH and high ionic strength.…”

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportmentioning

confidence: 99%

See 2 more Smart Citations

Humic Acid Transport in Water-Saturated Porous Media

Wei

Shao

Horton

et al. 2009

Environ Model Assess

View full text Add to dashboard Cite

The presence of humic acid (HA) in water poses environmental problems because it enhances the transport of several contaminants. A series of column experiments was conducted toward studying HA transport in different porous media under various pH, ionic strength, and flow rate conditions. The results showed that decreasing pH and increasing ionic strength increased adsorption and therefore delayed the transport of HA in porous media. However, increasing flow rate accelerated the transport of HA in porous media. The effects of pH, ionic strength, and flow rate varied with the solid matrix and were more evident in sands of smaller average particle diameter than in those with larger ones. These factors must be considered when predicting the environmental fate of HA. The results also suggested that HA adsorption was an important process controlling HA transport and should be considered in studies of HA behavior in porous media.

show abstract

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportsupporting

confidence: 88%

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportmentioning

confidence: 90%

Section: Effects Of Solution Ph and Ionic Strength On Ha Transportmentioning

confidence: 99%

See 1 more Smart Citation

Humic Acid Transport in Water-Saturated Porous Media

Wei

Shao

Horton

et al. 2009

Environ Model Assess

View full text Add to dashboard Cite

show abstract

“…Possessing a large number of free hydroxyl and carboxylic functional groups, the humic 277 acid layer can be highly hydrated (Wang et al 2001). These hydrated humic acid molecules 278 can block the membrane pores and enhance solute rejection by steric hindrance, which 279 reduces solute transport through the membrane.…”

Section: [Figure 2] 276mentioning

confidence: 99%

Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis

et al. 2013

View full text Add to dashboard Cite

The impact of humic acid fouling on the membrane transport of two pharmaceutically active compounds (PhACs) -namely carbamazepine and sulfamethoxazole -in forward osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was promoted by the complexation with calcium ions in the feed solution and the increase in ionic strength at the membrane surface due to the reverse transport of NaCl draw solute. The increase in the humic acid deposition on the membrane surface led to a substantial decrease in the membrane salt (NaCl) permeability coefficient but did not result in a significant decrease in the membrane pure water permeability coefficient. As the deposition of humic acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of water molecules. The membrane water and salt (NaCl) permeability coefficients were fully restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate into the membrane pores. Abstract 16The impact of humic acid fouling on the membrane transport of two pharmaceutically 17 active compounds (PhACs) -namely carbamazepine and sulfamethoxazole -in forward 18 osmosis (FO) was investigated. Deposition of humic acid onto the membrane surface was 19 promoted by the complexation with calcium ions in the feed solution and the increase in ionic 20 strength at the membrane surface due to the reverse transport of NaCl draw solute. The 21 increase in the humic acid deposition on the membrane surface led to a substantial decrease 22 in the membrane salt (NaCl) permeability coefficient but did not result in a significant 23 decrease in the membrane pure water permeability coefficient. As the deposition of humic 24 acid increased, the permeation of carbamazepine and sulfamethoxazole decreased, which 25 correlated well with the decrease in the membrane salt (NaCl) permeability coefficient. It is 26 hypothesized that the hydrated humic acid fouling layer hindered solute diffusion through the 27 membrane pore and enhanced solute rejection by steric hindrance, but not the permeation of 28 water molecules. The membrane water and salt (NaCl) permeability coefficients were fully 29 restored by physical cleaning of the membrane, suggesting that humic acid did not penetrate 30 into the membrane pores. 31

show abstract

“…Indeed, additional measurements (not shown) revealed that the organic content of both the extract and the solid residue decreased for extraction times from 12 h to 24 h. Figure 1 also shows that the TOC EX is higher for lower KOH concentration, expressed as the feed ratio K 2 O/TOC FEED . It is likely that the higher extraction rates are due to a faster diffusion coefficient for humic acids, which in turn are associated with a favorable conformation of the humic acid molecules in solution at lower pH and ionic strength values (Wang et al, 2001). Figure 2 shows that the TOC EX is higher when TOC FEED is higher, that is, more HSs are extracted when the peat is richer in organic matter.…”

Section: Exploratory Extraction Experimentsmentioning

confidence: 99%

Alkaline extraction of humic substances from peat applied to organic-mineral fertilizer production

Saito¹,

Seckler

2014

Braz. J. Chem. Eng.

View full text Add to dashboard Cite

-An organic-mineral fertilizer based on humic substances (HSs) and potassium was developed based on the alkaline extraction of HSs from peat. The HSs have interesting properties for use as a fertilizer since they improve the physical and chemical structure of the soil and provide a source of organic carbon which is readily absorbable by the plants, whereas potassium is a primary nutrient for plants. It was found that highly decomposed peats containing a small inorganic fraction are more favorable for the extraction of HSs. Using these peats, organic-mineral fertilizers that meet the Brazilian legislation have been obtained for a peatextractant mixture containing 2.57 wt% total organic content (TOC), a K 2 O/TOC ratio of 1 wt% and an extraction time of 12 hours.

show abstract

The effects of pH and calcium on the diffusion coefficient of humic acid

Cited by 110 publications

References 21 publications

Humic Acid Transport in Water-Saturated Porous Media

Humic Acid Transport in Water-Saturated Porous Media

Impact of humic acid fouling on membrane performance and transport of pharmaceutically active compounds in forward osmosis

Alkaline extraction of humic substances from peat applied to organic-mineral fertilizer production

Contact Info

Product

Resources

About