Effect of Humic Acid on Pyrene Removal from Water by Polycation-Clay Mineral Composites and Activated Carbon

Abstract

Pyrene removal by polycation-montmorillonite (MMT) composites and granulated activated carbon (GAC) in the presence of humic acid (HA) was examined. Pyrene, HA, and sorbent interactions were characterized by FTIR, fluorescence and zeta measurements, adsorption, and column filtration experiments. Pyrene binding coefficients to the macromolecules were in the order of PVPcoS (poly-4-vinylpiridine-co-styrene) > HA > PDADMAC (poly diallyl-dimethyl-ammonium-chloride), correlating to pyrene-macromolecules compatibility. Electrostatic interactions explained the high adsorption of HA to both composites (∼100%), whereas HA adsorption by GAC was low. Pyrene removal by the composites, unlike GAC, was enhanced in the presence of HA; removal by PDADMAC-MMT increased from ∼50 (k d = 2.2 × 10 3 kg/L) to ∼70% (k d = 2.4 × 10 3 kg/L) in the presence of HA. This improvement was attributed to the adsorption of pyrene-HA complexes. PVPcoS-MMT was most efficient in removing pyrene (k d = 1.1 × 10 4 kg/L, >95% removal) which was explained in terms of specific π donor−π acceptor interactions. Pyrene uptake by column filters of GAC reached ∼50% and decreased to ∼30% in the presence of HA. Pyrene removal by the PVPcoS-MMT filter was significantly higher (100−85% removal), exhibiting only a small decrease in the presence of HA. The utilization of HA as an enhancing agent in pollutant removal is novel and of major importance in water treatment. ■ INTRODUCTIONPolycyclic aromatic hydrocarbons (PAHs) are a group of persistent hydrophobic contaminants that have been detected in aquatic systems all over the world and are included in the US EPA and the EU priority list of pollutants (e.g., benzo(a)pyrene limit in water is 0.0002 mg/L). 1,2 Fate and transport of hydrophobic organic pollutants (including PAHs) in the environment is strongly affected by interactions with dissolved organic matter (DOM). 3−5 These interactions depend on both the chemical and structural characteristics of the pollutant and of the DOM and on the characteristics of the environmental system. 6 Studies have shown that in environmental systems the fate of organic contaminants can vary greatly in terms of adsorption or mobility. Several studies have demonstrated higher solubility and mobility of the pollutants in the presence of DOM. 7−9 For example, a study on enhanced organic pollutant solubility by DOM demonstrated increased partitioning coefficients into DOM with a decrease in pollutant water solubility and DOM polarity. 7 On the other hand, other studies have shown that the presence of DOM increased sorption and immobilization of organic pollutants to soil sediments and solid surfaces. 9−11 RavAcha and Rebhun 1992 suggested that DOM tended to solubilize organic pollutants when the adsorption coefficients (of the DOM) to the clay were relatively low, while adsorption of the pollutants to the clay increased as the DOM adsorption coefficients to the clay increased. 9 A later study also emphasized this complex behavior; the adsorption of an insecticide to soils d...

Developing Polycation-Clay Sorbents for Efficient Filtration of Diclofenac: Effect of Dissolved Organic Matter and Comparison to Activated Carbon

“…Experiments were conducted as published previously. 27 DCF (1 mg/L in tap water at pH-7.4) filtration by columns of QPVPcS and PVPcS composites (0.15 ± 0.01 g/g) and GAC was studied (4 replicates). The flow rate was 2 mL/min, 600 mL solution were filtered per column equivalent to 30 pore volumes (PV).…”

“…Pyrene adsorption to a poly-4-vinylpyridine-co-styrene (PVPcS)-clay composite was high and increased in the presence of humic acid (HA) which was explained by the high affinity of HA to the composite and a cosorption mechanism. 27 In contrast, pyrene removal by GAC decreased in the presence of HA. Zedaka et al 28 demonstrated the efficient removal of atrazine by protonated PVPcS (HPVPcS)-clay composites.…”

A Stepwise-Cluster Inference Model for Phenanthrene Immobilization at the Aqueous/Modified Palygorskite Interface

“…By gradually increasing the HA concentration to 80 mg OC/L, the retention of phenanthrene was hindered from 0.460 to 0.416 mg/g. At a low HA dose, the initial phenanthrene sorption increase was presumably due to the binding of phenanthrene to HA along with the sorption of HA onto modified palygorskite, forming a complexation of sorbed HA with phenanthrene [38]. The hydrophobic interaction mechanism was reported as the major factor responsible for the binding of PAHs to HA [39].…”

Designing a regenerable stimuli-responsive grafted polymer-clay sorbent for filtration of water pollutants

“…In addition, the pyridine group of the polymer can be further functionalized to improve composite performance [13,14]. Indeed, adsorbed functionalized PVP–MMT composites were efficient sorbents for filtration of a variety of pollutants including dissolved organic matter [14], pyrene [15], phenolic derivatives [16], pharmaceuticals [13] and pesticides [12,17]. …”