Adsorption Of 2-methylisoborneol Research Articles

Geosmin and 2-methylisoborneol adsorption using different carbon materials: Isotherm, kinetic, multiple linear regression, and deep neural network modeling using a real drinking water source

High concentrations of geosmin (GSM) and 2-methylisoborneol (MIB) caused by cyanobacterial blooms are problematic issues in drinking water treatment plants on the Nak-Dong River in South Korea. The goal of this study was to identify the best-performing carbon materials to treat GSM and MIB in river water and to predict the final concentrations of GSM and MIB according to different water quality parameters using computational predictive modeling, multiple linear regression (MLR), and a deep neural network (DNN) for practical applications. Three types of powdered activated carbon (PAC) and three types of mesoporous carbon (MC) were compared in terms of their adsorption capacities using a source of drinking water from the Nak-Dong River. The highest maximum adsorption capacities were achieved when using C-PAC (1485.06 μg/g) in both distilled water and river water. C-PAC possesses a high micropore volume (0.45 cm3/g), low mesopore volume (0.11 cm3/g), and small, narrow pore size distribution, yielding optimal adsorption conditions. PACs yielded better results than MCs because dominant mesopore structures can hinder the adsorption of small molecules (0.6–0.8 nm) and allow them to pass through pores. GSM was removed more effectively than MIB because GSM is more hydrophobic and has a flatter structure. The high dissolved organic carbon concentration in the river water caused no reduction in GSM and MIB adsorption, but actually enhanced adsorption because a small portion of natural organic matter can compete with adsorption sites and provide additional adsorption sites based on the shrunk pore effect. The MLR and DNN models were used to predict the removal efficiency of C-PAC for GSM and MIB using 72 individual datasets with cross-validation for robust prediction and sensitivity analysis. MLR predicted the relationships between the input variables and GSM and MIB concentrations with an acceptable mean absolute error (MAE) of 6.43 ng/L for GSM and 5.80 ng/L for MIB. However, the DNN provided better agreement with a higher R2 value (>0.99) and lower MAE of 1.67 ng/L for GSM and 1.24 ng/L for MIB.

Effects of pre, post, and simultaneous loading of natural organic matter on 2-methylisoborneol adsorption on superfine powdered activated carbon: Reversibility and external pore-blocking

Three different natural organic matter (NOM)-loading methods were compared for the adsorptive removal of 2-methylisoborneol (MIB) by superfine powdered activated carbon (SPAC) and conventionally-sized powdered activated carbon (PAC). The three NOM-loading methods were: NOM adsorption followed by MIB (MIB adsorption on NOM-preloaded carbon), MIB adsorption followed by NOM (MIB adsorption on NOM post-loaded carbon), and simultaneous NOM and MIB loading (MIB adsorption on NOM-simultaneously loaded carbon). MIB removals were similar for the smaller-sized carbon (SPAC) at higher AC dosages and at lower initial NOM concentrations. The similar MIB removals indicate direct site competition between MIB and NOM with MIB adsorption reversibility (complete desorption of MIB by NOM). At lower AC doses, especially for PACs, and at higher initial NOM concentrations, the adsorption of MIBs depended on the sequence of MIB or NOM adsorption. MIB removal was lowest for the NOM-preloaded carbon, followed by NOM-simultaneously loaded carbon. The highest MIB removal was achieved by post-loading of NOM, indicating that the adsorption is irreversible. MIB adsorption on SPAC was more reversible than on PAC, although the pore size distributions of the two carbons were similar. The high degree of adsorption irreversibility for PAC compared with SPAC indicated that pore blocking occurs due to NOM loading at the PAC particle surface. Images of the external adsorption were obtained using isotope mapping and 15N-labeled effluent organic matter.

Projecting competition between 2-methylisoborneol and natural organic matter in adsorption onto activated carbon from ozonated source waters

Though the ozone-activated carbon process has been widely applied for drinking water purification, little is known about how ozone-modified natural organic matter (NOM) competes with micropollutants in activated carbon adsorption. In this study, three natural waters and one synthetic water (standard humics solution) with highly heterogeneous NOM compositions were employed to investigate the interference of ozonated NOM with the adsorption of 2-methylisoborneol (MIB). Analysis using liquid chromatography with online carbon and UV254 detection (LC-OCD-UVD) revealed that ozonation led to various disintegration patterns of macromolecules in NOM, and UV absorbance was reduced markedly for nearly all NOM fractions. Powdered activated carbon (PAC) adsorption experiments showed that increasing ozone consumption coincided with reducing NOM competition against MIB in the three natural waters, as expressed by the fitted initial concentrations of the equivalent background compound (c0,EBC). In the synthetic water, in contrast, competition increased under low/moderate specific ozone consumptions and then decreased with further elevation of ozone consumptions. Regarding the significance on affecting ozonated NOM interference, aromaticity reduction outweighed formation of low molecular weight (LMW) organics in most cases, enhancing MIB adsorption capacity. However, disintegration of the humics fraction with larger molecular weight (1,103 g/mol, as compared to 546–697 g/mol in three natural waters) into smaller, more competitive fractions caused the observed initial deteriorated MIB adsorption in synthetic water. A superior correlation between c0,EBC and the UV absorbance of LMW organics (R2 = 0.93) over concentrations of LMW organics underlined the importance of the aromatic properties in competitive adsorption projection for ozone pretreated natural waters. Furthermore, the change of relative concentration of UV absorbing compounds during ozonation could help estimate the decrease of c0,EBC, which could be a promising tool for waterworks to adjust PAC doses for MIB removal in ozonated waters.

Adsorption of 2-methylisoborneol and geosmin by a low-cost hybrid adsorbent synthesized from fly ash and bentonite

This paper describes the synthesis of a low-cost hybrid adsorbent from activation of fly ash and bentonite to remove 2-methylisoborneol (MIB) and geosmin from water. These substances produce objectionable taste and odor problems at levels as low as 4–10 ng/L and an effective, low-cost method of removal would be useful. The effect of the initial pH, contact time and adsorbent dosage on the adsorption process was investigated. In the range of 42–234 ng/L of MIB and geosmin, the maximal adsorption efficiency was obtained at the conditions of a dose level of 15 mg/L adsorbent, pH 8 and 60 min contact time, reaching 59.9 and 63.7%, respectively. Comparing to the natural fly ash and bentonite, the adsorbent showed higher surface area and micropores. The interlayer distance of the hybrid adsorbent was 0.59 nm, in accord with the molecular dimension of MIB and geosmin. The effect of humic acid, representative of natural organic matter (NOM), on MIB and geosmin adsorption was investigated for absorbent systems and indicated the presence of NOM would decrease adsorption slightly. The leaching experiments showed that the leaching of heavy metals from the adsorbent was negligible.

Adsorption of 2-Methylisoborneol in Drinking Water by Different Granular Carbons

Three kinds of granular carbon made from different materials of coal, coconut shell and jujube seed were evaluated for adsorption of 2-methylisoborneol in drinking water by equilibrium isotherm simulation. Results showed that Freundlich isotherm can more suitable to describe the adsorption of these three kinds of carbon. For coal-based, coconut shell and jujube seed carbon, the largest adsorption capacity of 2-MIB were 2225.0，3152.8 and 1E-07（ng/g）(L/ng)n respectively in pure water, and in raw water they were 559.6，612.5 and 6E-28（ng/g）(L/ng)n respectively, about one-fifth of those in pure water. Among the selected carbons, coconut shell carbon had the largest adsorption capacity, followed by coal-based and jujube seed carbon which can hardly absorb 2-MIB.

Geosmin and 2-methylisoborneol adsorption on super-powdered activated carbon in the presence of natural organic matter

Geosmin and 2-methylisoborneol (2-MIB) are naturally occurring compounds responsible for musty-earthy-odors in surface water supplies. They are a severe problem confronting utilities worldwide. Adsorption by powdered activated carbon (PAC) is a widely used process to control this problem, but it has low efficiency, which engenders large budget spending for utilities services. Super-powdered activated carbon (S-PAC) is activated carbon with much finer particles than those of PAC. Experiments on geosmin and 2-MIB adsorptions on S-PAC and PAC were conducted. Geosmin and 2-MIB adsorption capacities on S-PAC were not smaller than those on PAC although natural organic matter, which adversely impacted the adsorption capacity of geosmin and 2-MIB, was more adsorbed on S-PAC than on PAC, meaning that the adsorption competition is less severe for S-PAC than for PAC.

The role of surface acidity and pore size distribution in the adsorption of 2-methylisoborneol via powdered activated carbon

Powdered activated carbon (PAC) is a common answer to water utilities’ taste and odor problems. However, these utilities are often uncertain as the characteristics of PAC are critical for optimum taste and odor abatement. In order to separate the effects, if any, that pore structure and surface chemistry have on the adsorption of the odorant 2-methylisoborneol (MIB), two sets of carbons were created: five physically activated (PA)-PACs, with different pore size distributions and similar surface chemistries, and four chemically treated (CT)-PACs with similar pore structures and different surface chemistries. Nitrogen adsorption, reverse mass titrations, and Boehm titrations were used to characterize the physical and chemical attributes of the carbons. Batch tests utilized 14C-MIB and contact times resembling those found at water utilities. The pore size distributions and the percent removal of MIB for the PA-PACs indicated that a range of micro- and meso-pores (12–100 Å) were necessary regardless of natural organic matter (NOM) concentration. The performance of the CT-PACs indicated that surface chemistry did affect MIB removal, but differently depending on the concentration of NOM. In DI water, surface acidity had a strong inverse relationship with MIB removal, but increasing NOM levels lowered the impact of the acidic functional groups. In fact, in a Florida raw water, surface chemistry demonstrated no effects on adsorption as all CT-PACs performed equally.

Adsorptive ozonation of 2-methylisoborneol in natural water with preventing bromate formation

This paper presents an application of our newly developed adsorptive ozonation process using a high silica zeolite adsorbent (USY) for drinking water treatment. First, the adsorption of 2-methylisoborneol (2-MIB) on USY in a river water/pure water mixture was clarified by a batch-type adsorption experiment. The results showed that 2-MIB was adsorbed on USY; however, almost all of the adsorbed 2-MIB was desorbed over time. The desorption rate was increased with the ratio of river water to pure water, indicating that compounds dissolved in the river water, such as natural organic matter (NOM), prevent the adsorption of 2-MIB on USY. Second, the ability of the river water to consume ozone was confirmed in an experiment using a USY-packed column reactor. The ozone consumption was obviously increased by the presence of USY, indicating that USY-adsorbing compounds dissolved in the river water (probably small size NOM) consumed the ozone. However, the rapid ozone consumption was occurred by 6–8 s in the retention times when 3.14–4.38 mg L −1 of water dissolved ozone was fed, this rapid ozone consumption lasted no more than these times. This result revealed that the rapid consumption of ozone by the adsorptive compounds in our process could be avoided within a certain retention time (6–8 s; especially for the river water used in this study) when enough concentration of ozone (3.14 mg L −1 or more; same above) was supplied. We therefore performed a trial in which 2-MIB dissolved in river water was continuously decomposed using a USY-packed column with various ozone concentrations. In the process, the adsorptive compound dissolved in the river water adsorbed and reacted with ozone in the parts of the apparatus upstream of the column, while the adsorption and decomposition of 2-MIB took place in the parts of the apparatus downstream of the column. This resulted in a sufficient 2-MIB decomposition with minimizing bromate ion formation.

Influence of characterised natural organic material on activated carbon adsorption: II. Effect on pore volume distribution and adsorption of 2-methylisoborneol

The adsorption of four ultrafiltration fractions of natural organic material (NOM) had a significant effect on the surface area and pore volume distributions of a coal-based activated carbon. This effect was dependent on the size of the compounds; the smaller fraction had the greatest effect on the micropore volume, and the larger fractions had a greater effect on the mesopore volume. Only the mesopore volume of a wood-based activated carbon was reduced by adsorption of the NOM fractions. The competitive adsorption between five NOM ultrafiltration fractions and 2-methylisoborneol (MIB) was greatest for the smallest fraction (ultrafiltration molecular weight <500), as this fraction was the most similar in size to MIB and therefore provided direct competition for the same adsorption sites. The NOM in a natural water sample displayed the greatest competition with MIB, due to the presence of small compounds that were lost during the concentration and desalting procedures used to obtain the NOM fractions. The competition between MIB and the largest ultrafiltration fraction was very small and could probably be attributed to smaller compounds present in this fraction.