Sorption of Organic Compounds to Fresh and Field-Aged Activated Carbons in Soils and Sediments

Abstract

Activated carbon (AC) amendment to polluted sediment or soil is an emerging in situ treatment technique that reduces freely dissolved porewater concentrations and subsequently reduces the ecological and human health risk of hydrophobic organic compounds (HOCs). An important question is the capacity of the amended AC after prolonged exposure in the field. To address this issue, sorption of freshly spiked and native HOCs to AC aged under natural field conditions and fresh AC amendments was compared for one soil and two sediments. After 12-32 months of field aging, all AC amendments demonstrated effectiveness for reducing pore water concentrations of both native (30-95%) and spiked (10-90%) HOCs compared to unamended sediment or soil. Values of K(AC) for field-aged AC were lower than freshly added AC for spiked HOCs up to a factor of 10, while the effect was less for native HOCs. The different behavior in sorbing native HOCs compared to freshly spiked HOCs was attributed to differences in the sorption kinetics and degree of competition for sorption sites between the contaminants and pore-clogging natural organic matter. The implications of these findings are that amended AC can still be effective in sorbing additional HOCs some years following amendment in the field. Thus, a certain level of long-term sustainability of this remediation approach is observed, but conclusions for decade-long periods cannot be drawn solely based on the present study.

Extraction of sediment‐associated polycyclic aromatic hydrocarbons with granular activated carbon

“…Our current results suggest sorption attenuation of HOCs to GAC, as observed in earlier studies [12,22,23,43]. Two plausible competitive mechanisms, which might be responsible for the fouling of GAC, are direct site competition and pore blocking by dissolved organic carbon (DOC) [22,23].…”

Effect of activated carbon and biochars on the bioavailability of polycyclic aromatic hydrocarbons in different industrially contaminated soils

“…The f sorbent is the fraction of the OC in the soil plus the individual sorbent. The Freundlich exponent of sorption to the different chars (n F,sorbent ) was assumed to be 0.8, under the assumption that the main sorption mechanisms are similar for various PAHs in the same sorbent material (Oen et al 2012). All comparisons were evaluated using a one-way analysis of variance (ANOVA) and by a t tests at a 95 % confidence level.…”

Sorption/desorption of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane(4,4′-DDT) on a sandy loam soil

“…A recent study with fresh and field-aged activated carbon also reported that DDT sorption-desorption was highly dependent on the contact time between contaminant and sorbent. Aged activated carbon sorbed up to 10 % more than freshly spiked carbons (Oen et al 2011). Soil parameters affecting desorption of DDT were stated to be % organic matter, amount of dissolved organic carbon, surface area, % clay/silt, and pH levels (Ghazali et al 2010;Holoubek et al 2009;Oen et al 2011;Thangavadivel et al 2011).…”

“…Aged activated carbon sorbed up to 10 % more than freshly spiked carbons (Oen et al 2011). Soil parameters affecting desorption of DDT were stated to be % organic matter, amount of dissolved organic carbon, surface area, % clay/silt, and pH levels (Ghazali et al 2010;Holoubek et al 2009;Oen et al 2011;Thangavadivel et al 2011). For instance, relatively low pH values (pH=5.4) were said to cause stronger hydrogen bonding when compared to neutral or alkali pH conditions (Boivin et al 2005;Thangavadivel et al 2011).…”