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Recent interest has arisen in the use of biochar as a low-cost adsorbent for control of organic micropollutants in water. However, compared with activated carbon (AC), biochar adsorption capacity is typically one to two orders of magnitude lower. This study reports batch mode adsorption of anionic (2,4-D, C0 100 μg/L) and neutral (simazine [SZN], C0 1.5 μg/L) herbicides from surface water containing dissolved organic matter at 4 mg/L total organic carbon concentration. Enhanced adsorption was observed by biochars generated from updraft gasifiers under conditions of simultaneous co-pyrolysis thermal air activation (CPTA). 2,4-D adsorption by ≥850°C CPTA biochars was more than 10 times greater on a mass basis compared with biochars generated from a conventional anoxic pyrolysis (CAP) reactor and was equivalent to AC reference adsorbents on a surface area normalized basis. Biochars generated at ≥850°C under CPTA conditions had similar micropore surface area to CAP biochars (∼330 m2/g) but about 2.5 times the mesopore surface area (∼110 m2/g CPTA, ∼40 m2/g CAP), suggestive of increased pore accessibility generated by thermochemical widening of pores and/or removal of pyrolysis tars by CPTA. 2,4-D adsorption from surface water was shown to correlate strongly with biochar H:C molar ratio within but not between biochars grouped by CAP and CPTA generation conditions. Comparing adsorption of 2,4-D and SZN by biochars generated from CAP and CPTA conditions suggested that herbicide interaction with biochar surface functional groups through formation of charge-assisted H-bonds did not play a significant role in herbicide uptake from surface water. [ABSTRACT FROM AUTHOR]

Cyclohexanol, phenol, benzoic acid, and phenanthrene fractional removal (italicized words are defined within the main text) by pulverized granular activated carbon and biochar adsorption in deionized water and stormwater was independent of target-adsorbate initial concentrations (C0) when C0s were below concentration thresholds. This permits a simple-modeling approach. C0-independent removal in deionized water at low-target-adsorbate concentrations potentially suggests that DOM in the deionized water induce a competitive effect that causes deviations from the Freundlich model. The Ideal Adsorbed Solution Theory-Equivalent Background Compound model was used to determine the magnitude of concentration thresholds and the competitive effect of stormwater DOM and possibly deionized water DOM. These competing substances' competitive effects were influenced by target-compound adsorbability and structure. Concentration thresholds positively correlate with competing substances' competitive effect and negatively correlate with target-adsorbate-Freundlich 1/n values. In deionized water, concentration thresholds increase as target-compound adsorbability decreases. In stormwater, concentration thresholds do not correlate with adsorbability, potentially because stormwater DOM is better suited to compete for aromatic-compound-adsorption sites. The extent known-competitor adsorbates decrease target-adsorbate removal in the presence of DOM is investigated, which depends on the competing adsorbates' relative adsorbabilities and if they adsorb to a different subpopulation of adsorption sites. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) negatively impacts granular activated carbon (GAC) adsorption of micropollutants and is a disinfection byproduct precursor. DOM from surface waters, wastewater effluent, and 1 kDa size fractions were adsorbed by GAC and characterized using fluorescence spectroscopy, UV-absorption, and size exclusion chromatography (SEC). Fluorescing DOM was preferentially adsorbed relative to UV-absorbing DOM. Humic-like fluorescence (peaks A and C) was selectively adsorbed relative to polyphenol-like fluorescence (peaks T and B) potentially due to size exclusion effects. In the surface waters and size fractions, peak C was preferentially removed relative to peak A, whereas the reverse was found in wastewater effluent, indicating that humic-like fluorescence is associated with different compounds depending on DOM source. Based on specific UV-absorption (SUVA), aromatic DOM was preferentially adsorbed. The fluorescence index (FI), if interpreted as an indicator of aromaticity, indicated the opposite but exhibited a strong relationship with average molecular weight, suggesting that FI might be a better indicator of DOM size than aromaticity. The influence of DOM intermolecular interactions on adsorption were minimal based on SEC analysis. Fluorescence parameters captured the impact of DOM size on the fouling of 2-methylisoborneol and warfarin adsorption and correlated with direct competition and pore blockage indicators. [ABSTRACT FROM AUTHOR]

This study examined sorption of the human and veterinary antibiotic sulfamethoxazole (SMX) at environmentally relevant concentrations from laboratory clean water, surface water, stormwater, and wastewater effluent to wood and wastewater-sludge derived biochars produced under a wide range of conditions. SMX sorption by commercial powdered activated carbon (PAC) was also quantified as a benchmark. Wood-based biochar produced around 850 °C performed similarly to PAC. Biochar sorption capacity increased with surface area up to ∼400 m 2 /g. However, a further increase in surface area did not correspond to an increase in sorption capacity. Sorbent H:C ratios correlated with SMX uptake by PAC and wood-based biochars, but not for the sludge-based biochars. This is possibly due to an indirect influence of the high ash content in sludge-based biochars, as the isolated ash fraction exhibited negligible SMX sorption capacity. The presence of dissolved organic matter (DOM) in the natural and anthropogenic waters fouled most of the sorbents (i.e., decreased SMX uptake). The sludge-based biochars experienced less DOM fouling relative to wood-based biochar, particularly in the wastewater effluent. Biochar and PAC sorption kinetics were similar when examined over a contact time of four-hours, suggesting their performance ranking would be consistent at contact times typically utilized in water treatment systems. In the presence of DOM, SMX relative removal (C/C 0 ) was independent of SMX initial concentration when the initial concentration was below 10 μg/L, thus permitting the relative removal results to be applied for different SMX initial concentrations typical of environmental and anthropogenically impacted waters. [ABSTRACT FROM AUTHOR]

This study demonstrates that the ideal adsorbed solution theory-equivalent background compound (IAST-EBC) as a stand-alone model can simulate and predict the powdered activated carbon (PAC) adsorption of organic micropollutants found in drinking water sources in the presence of background dissolved organic matter (DOM) under nonequilibrium conditions. The IAST-EBC represents the DOM competitive effect as an equivalent background compound (EBC). When adsorbing 2-methylisoborneol (MIB) with PAC, the EBC initial concentration was a similar percentage, on average 0.51%, of the dissolved organic carbon in eight non wastewater impacted surface waters. Using this average percentage in the IAST-EBC model yielded good predictions for MIB removal in two non wastewater impacted waters. The percentage of competitive DOM was significantly greater in wastewater impacted surface waters, and varied markedly in DOM size fractions. Fluorescence parameters exhibited a strong correlation with the percentage of competitive DOM in these waters. Utilizing such correlations in the IAST-EBC successfully modeled MIB and sulfamethoxazole adsorption by three different PACs in the presence of DOM that varied in competitive effect. The influence of simultaneous coagulant addition on PAC adsorption of micropollutants was also investigated. Coagulation caused the DOM competitive effect to increase and decrease with MIB and sulfamethoxazole, respectively. [ABSTRACT FROM AUTHOR]

• Biochar removes short-chain PFAS from groundwater, surface water, and wastewater. • New method achieves accurate simulation of full-scale PFAS removal from rapid benchtop testing. • UV and fluorescence parameters provide surrogate monitoring for PFAS removal in carbon adsorbers. • Cost-effective PFAS prediction and monitoring enabled for a variety of treatment applications. Carbon adsorbent fouling by dissolved organic matter (DOM) inhibits the ability of the widely-used rapid small-scale column test (RSSCT) to accurately predict the removal of organic micropollutants (OMP) from water by full-scale carbon adsorbers. Here, the adsorption of 11 short-chain per-/poly-fluoroalkyl substances (PFAS) from groundwater, surface water, and wastewater was examined in pilot columns as well as RSSCTs using constant diffusivity (CD) and proportional diffusivity (PD) designs. Neither the CD- or PD-RSSCT accurately predicted pilot adsorber breakthrough of PFAS using standard diffusional mass transfer models. However, PFAS breakthrough relative to optical property (e.g., peak C, UV absorbance at 254 nm) breakthrough remained constant between pilot column, CD-RSSCT, and PD-RSSCT designs. This finding permitted accurate breakthrough predictions for the sum of PFAS and for 9 of the 11 PFAS on an individual basis in pilot columns using RSSCTs. Multiple linear regressions incorporating influent and treated water optical parameters enabled the modeling approach to be applied to water sources with heterogeneous DOM characteristics. It is hypothesized that this methodology was successful because (i) optical parameters adequately quantified the competitive nature of DOM and their adsorption behaved similar to OMP and (ii) competitive adsorption by low-molecular weight DOM was the predominant fouling mechanism. An OMP monitoring approach was developed for waters containing DOM with heterogenous characteristics that also relied on raw and treated water optical properties. UVA 254 and fluorescence monitoring could therefore enable water treatment to remove PFAS in a variety of scenarios that face inhibitory cost and analytical limitations, such as decentralized and low-resource settings. [Display omitted] [ABSTRACT FROM AUTHOR]