Sorption Of Pentachlorophenol Research Articles

Quantification of the sorption of organic pollutants to minerals via an improved mathematical model accounting for associations between minerals and soil organic matter.

The retention of organic pollutant (OP) in soils is commonly attributed to interactions with soil organic matter (SOM), perhaps overlooking substantial involvement of soil minerals. In this study, 36 soil samples with far-ranging ratios of clay to organic carbon were used to examine contribution of minerals on soil sorption of pentachlorophenol (PCP) and phenanthrene (PHE). Sorption isotherms (n=216) were fit individually using three typical sorption models, with the most fitted Kd values screened out for quantification of the net mineral contribution to total sorption via development of mathematical model accounting for associations between minerals and SOM. Two mineral-relevant parameters [adsorption distribution coefficient (Kmin) and mineral contribution index (MCI)] were simultaneously defined. Previously reported soil sorption data of PCP, PHE and butachlor (13, 12 and 46, respectively) were also extracted and included to improve the credibility of mathematic model. The average MCI values were calculated as 0.421, 0.405 and 0.512 in PCP, PHE and butachlor treated soils, respectively, very close to or even over than the minerals dominant critical value (0.5). This suggested the significant, or even predominant, contribution of minerals - as compared to SOM. Significant dependence of MCI with four conventional parameters of soil property further offered the possibility to roughly evaluate mineral contributions based on estimated threshold values of soil property parameters (especially TOC). This study provides an accessible approach for predicting the contribution of minerals in soil OP retention, especially highlighting their predominant roles vs. SOM in regulating OP removal in most of subsurface soil or contaminated brownfields where organic carbon content of soil was very low, that was not like what previously believed.

Sorption of pentachlorophenol and phenanthrene by humic acid-coated hematite nanoparticles

Hematite nanoparticles (NPs) exist naturally and ubiquitously in soil, and they are always associated with soil organic matter by forming organic-inorganic complexes. In this work, hematite NPs coated with peat humic acid (HApeat) and soil humic acid (HAsoil) were chosen as sorbents for hydrophobic organic contaminants (HOCs) to simulate the sorption processes in soil. Ionizable pentachlorophenol (PCP) and non-ionizable phenanthrene (PHE) were selected as representative HOCs. Compared with sorption isotherms of uncoated hematite NPs, the coating of HA onto the surface of hematite NPs substantially increased its sorption affinity for PCP and PHE by about 1-2 orders of magnitude, and the increasing degree was positively correlated to the HA content. These phenomena emphasized the dominant role of HA in the sorption process. The reduced polarity and the introduction of functional groups contributed to the enhanced sorption of HOCs on HA-coated hematite NPs. Furthermore, HApeat-hematite NPs showed higher sorption affinity for both PCP and PHE than HAsoil-hematite NPs, which was mainly due to the lower polarity and higher hydrophobicity of HApeat-hematite NPs. The sorption of PCP and PHE on HA-coated hematite NPs was inhibited obviously with increasing pH values and the pH effect on PCP sorption was more significant than that of PHE, due to the deprotonation of functional groups within adsorbed HA, the loose structure of adsorbed HA and the dissociation of PCP. Our findings elucidated the mechanisms involved in HOCs sorption processes by HA-hematite NPs and provided a theoretical basis for environmental remediation with natural NPs (e.g., hematite NPs).

Effects of heavy metal species, concentrations, and speciation on pentachlorophenol sorption by river biofilms.

The sorption of trace organic pollutants at solid/liquid interfaces is one of the most important processes that influence their fate and behaviours in the aquatic environment. Sorption is affected by coexisting contaminants. The process and extent to which coexisting heavy metals affect the sorption of organochlorine pesticides (OCPs), especially acid radical anion heavy metals, are still unclear. Here, the effects of the species, concentrations, and speciation of the heavy metals Cu, Pb, and Cr, and the metalloid As on the sorption of pentachlorophenol (PCP), as a model OCP, by river biofilms were investigated through batch experiments. The results show that the presence of Cu, Pb, Cr, and As decreased the maximum sorption quantity of PCP onto the biofilms by 67.7, 9.2, 58.4, and 14.4%, respectively. The inhibitory effect of heavy metals on sorption decreased as the initial concentration ratios of heavy metals to PCP increased. In addition, the impact of heavy metals on PCP sorption was attributed to differences in heavy metal speciation. Cu and Pb commonly existed as divalent cations, but Cr and As existed as anionic acid radicals under the experimental conditions. The inhibitory effects of heavy metals on PCP sorption by biofilms were enhanced as the cation valence state increased, while the effects were weakened as the anionic acid radical valence state increased. Although all four heavy metals had inhibitory effects on PCP sorption by biofilms, there were distinct differences in the mechanisms causing these effects.

Sorption of pentachlorophenol (PCP) in the marine bottom sediments\u2014batch sorption experiment at varying pressure

Study was undertaken to determine the effect of hydrostatic pressure on the sorption of pentachlorophenol (PCP). The experiment was conducted at atmospheric pressure (1000 hPa) and at increased pressure (6000 hPa) simulating conditions at the water depth of 50 m. The sorption of PCP was examined in an artificial environment (microcosm) consisting of the marine water and the bottom sediments from a Polish harbor and the southern Baltic Sea. The first part of the experiment comprised the determination of PCP sorption parameters in the microcosms and parameters of the sediments (organic matter content, conductivity) and of the overlying water (pH, ion concentration) at 1000 hPa. The second part of the experiment was conducted at 6000 hPa inside the hyperbaric chamber. The hyperbaric exposure affected parameters of the harbor sediments and the overlying water but had little influence on the concentration of PCP in the microcosms containing the southern Baltic Sea sediments. Considering the specific characteristics of the harbor sediments, it can be assumed that the impact of hydrostatic pressure on the sorption process of PCP at 50-m depth appears to be negligible.

The role of extracellular polymeric substances on the sorption of pentachlorophenol onto natural biofilms in different incubation times: a fluorescence study

ABSTRACTExtracellular polymeric substances (EPS) have been regarded as the most significant components in sorbing organic contaminants onto natural biofilms. However, few investigations have reported the effects of EPS on the sorption of organic contaminants onto biofilms in different incubation times. Here, pentachlorophenol (PCP), selected as a model organic pollutant, was sorbed by biofilms and EPS-free biofilms cultured for 15, 30, and 45 days, to evaluate the role of EPS in the sorption process. EPS were extracted from biofilms to investigate the binding mechanism of PCP to the fluorescence matters in EPS by fluorescence quenching titration. Results showed that EPS, bound with biofilms or released to water, could increase or decrease the sorption amounts of PCP on biofilms in various incubation times. The presence of bound EPS in biofilms enhanced the sorption amounts of 30-day biofilms (6.0 ± 0.11 μmol g−1) because of the formation of the EPS-PCP complex between PCP and fluorescence matters in EPS, such as protein-like matters. In contrast, the release of PCP-bound EPS in 15- and 45-day biofilms decreased the sorption amounts of PCP on biofilms. All the results suggested that EPS dominated the sorption of PCP onto biofilms.

Sorption behaviour of pentachlorophenol in sub-Saharan tropical soils: soil types sorption dynamics

In order to predict exposure risks as well as appropriate remediation strategies for pesticides in soils, knowledge of pesticides sorption processes onto various representative soils is vital. Hence, laboratory batch experiments were carried out to study sorption of a pesticide, pentachlorophenol (PCP), on five soils obtained from different sub-Saharan agro-ecological zones (AEZs) in order to understand sorption equilibrium, kinetics, and thermodynamics. Experimental data showed that sorption equilibrium was attained within 24 h. The fitting of kinetic results and equilibrium data to different models suggested partly surface adsorption and partly partitioning of PCP within voids of the various soil components. Sorption was mainly attributed to sharing or exchange of valence electrons between negatively charged PCP molecules and positively charged soil sorption sites. The sorption process was spontaneous and accompanied by decreased entropy, but was pH and temperature dependent, reducing with increase in pH and temperature. The various soils’ PCP sorption capacities were directly proportional to their cation exchange capacities. The low PCP sorption observed in these soils suggested high risk of PCP being present in soil water solution, especially at higher temperatures, which can lead to contamination of the aquifer. This risk may be higher for soils obtained from AEZs with warmer natural temperatures.

Distribution and interactions of pentachlorophenol in soils: The roles of soil iron oxides and organic matter

Soil iron oxides (IOs) and organic matter (OM) play varying roles in pentachlorophenol (PCP) retention and mobility, but the extent and mechanism are still unknown. Therefore, in order to have a better understanding of the adsorption of PCP on soils, batch sorption studies were carried out on whole soils and soils selectively treated to remove IOs (IOR) and OM (OMR). The effects of pH, time, and temperature were investigated. Results showed that PCP sorption was temperature and pH dependent; sorption decreased as both temperature and pH increased. Sorption was partly surface adsorption and partly partitioning within voids of IOs components as revealed by the kinetics models. The surface adsorption was multi-layer in nature. Equilibria were faster in the IOR soils than the untreated and OMR soils. IOs played greater roles in PCP sorption than OM. Removal of soil components, especially the IOs, as experienced in soils plagued by soil erosion, may lead to increased risks of PCP pollution of environmental media especially the aquifer.

Interactive influence of Fe–Mn and organic matter on pentachlorophenol sorption under oxic and anoxic conditions

This study examined the adsorption of pentachlorophenol (PCP) on geosorbents (original bulk soil and soils treated to significantly remove organic carbon and oxides of Fe and Mn) under oxic and anoxic experimental conditions. pH effects on adsorption capacities were maximal at pH<pKa of PCP (4.7). Decrease in redox potential and an increase in dissolve organic carbon inhibited PCP sorption. While contribution of Mn oxide to PCP sorption was negative due to decreasing charge interference, the study equally implied negligible role of surface area compared to organic matter contents and oxides of Fe with R2≤0.825. The rate of Fe2+ and Mn2+ release under anoxic condition reduced interactions of phenolate with iron oxides and consequently, the distribution coefficients coupled with increased dissolve organic carbon. Pseudo second order and Langmuir isotherm provided the best kinetic and isotherm models respectively, although adsorption processes appeared to involve more than one kinetic stage based on intra-particle diffusion model (R2≤0.982). The study suggests that soil treatment to remove Mn oxide may encourage transitory PCP sinks in some reductomorphic environments.

The change of organic matter in sewage sludge composting and its influence on the adsorption of pentachlorophenol (PCP).

Due to the abundance of organic matter in compost, the addition of compost to soil can promote the adsorption of pesticides. However, few studies have examined the influence of the composting duration on the organic matter (OM) transformation and adsorption capacity of the compost. In this study, a mixture of sewage sludge and straw was composted, and then the physicochemical properties of various OM were studied. Additionally, the sorption capacities of humic acid (HA), humin (HM), humic acid + humin, and fulvic acid (FA) + humic acid + humin extracted from composts of different stages toward pentachlorophenol (PCP) were compared. The sorption data can be well-described by the Freundlich model, and the sorption capacity of PCP on HM is the strongest of all organic components. After 120 days of composting, the sorption abilities of HA and HM increased by 54.76 and 36.73%, respectively, which corresponds with increases in the aromatization degree, BET specific area, and pore volume and with a decrease in acid functional groups. The sorption ability of HA and HM increased by 54.76 and 36.73% due to the increase of the aromatization degree. However, the sorption capacity of the compost decreased by 51.2%, which resulted from a decrease in total organic matter content and from the interaction between organic components in composts. This could be verified by the sequence of the sorption capacity: HM > HM + HA > HM + HA + FA > HA. The contribution of humus to the sorption of PCP onto compost is approximately 41 to 55%, and it increases with composting time. Therefore, it is possible that other components are present that affect the adsorption of PCP on composts.

Amphiphilic compounds enhance the dechlorination of pentachlorophenol with Ni/Fe bimetallic nanoparticles

Abstract Pentachlorophenol (PCP), a general ionized chlorinated aromatic contaminant, was treated with Ni/Fe nanoparticles (NPs). An increase in the Ni/Fe dosage enhanced the removal of PCP. The most effective nickel percentage was 0.5%. Among the selected surfactants including carboxymethyl cellulose, Triton X-100, and cetyl trimethylammonium bromide (CTAB), CTAB markedly enhanced the removal of PCP by Ni/Fe. From removal kinetics, increased sorption of PCP onto Ni/Fe surfaces with CTAB was observed when compared to that without CTAB. This is the result of the small particle size of Ni/Fe-CTAB and the electrostatic interaction between an electronegative phenolate group of PCP and the electropositive Ni/Fe-CTAB. The increased sorption of PCP onto Ni/Fe surfaces by CTAB accelerated the reduction of PCP. In addition, with CTAB, the observed bulky and soft surface of Ni/Fe NPs allows enhanced electron transfer from the zerovalent iron core. The removal mechanism of PCP is dechlorination for Ni/Fe-CTAB but, for bare Ni/Fe, adsorption is mainly responsible for the removal. The dechlorination pathways of PCP with Ni/Fe-CTAB were investigated. The ortho position of chloride can be more easily reduced than other positions. Ni/Fe-CTAB NPs have a high potential to treat polychlorinated aromatics.

Pentachlorophenol Sorption by Rhizopus oryzae ENHE: pH and Temperature Effects

In this work, the sorption of pentachlorophenol (PCP) by non-viable biomass of Rhizopus oryzae ENHE was evaluated. The kinetics and isotherm studies were performed at pH 5.0, 6.0, and 8.0. The point of zero charge of the biomass was determined; this value allowed us to explain the changes of pH during sorption studies. The analyzed experimental kinetic data revealed that Ho’s model adjusted better to the experimental data than Lagergren’s model. PCP sorption was fast; an equilibrium sorption time was reached within 30 min, regardless of pH. PCP sorption at pH 5.0 and 6.0 was better described by the Freundlich isotherm than by the Langmuir isotherm. In contrast, at pH 8.0, the Langmuir isotherm describes better the PCP sorption. Sorption data showed that at pH 5.0 and 6.0, the sorption capacity of PCP was higher than at pH 8.0. Sorption of PCP by the fungal biomass occurred spontaneously; it was endothermic and due to physical sorption. Finally, FT-IR analysis of the dried biomass indicated that amino and hydroxyl groups were involved in the sorption of PCP. This work is one of the few reporting the effect of pH and temperature on the sorption of PCP by microbial biomass from a filamentous fungus belonging to the genus Rhizopus.

Biochar enhances the microbial and chemical transformation of pentachlorophenol in paddy soil

It is widely believed that biochar plays an important role in sequestrating pollutants in soil. The impacts of biochar on soil microbial community structure, and consequently on the environmental fate of soil pollutants, however, remains poorly understood. In this study, rape-straw derived biochar was used to investigate how biochar amendment affected microbial communities and pentachlorophenol (PCP) transformation in a paddy soil under anoxic conditions. PCP sorption and transformation and HCl-extractable Fe(II) generation were significantly enhanced in biochar amended soils. The results showed that the enhanced transferred extracellular electron in biochar amended soils promoted the PCP transformation while biochar supplement promoted the growth and metabolism of microorganisms in the soil. The relative abundance of dominant microbial population was bearing on biochar dosages in the soil. In addition, quantitative real-time PCR results illustrated that biochar acted as a growth stimulant for iron(III)-reducing and dechlorinating bacteria, which consequently promoted PCP biotransformation. Our findings indicated that rape-straw derived biochar may be an important agent for activating the soil functional microbial communities and can be used to environmental-friendly accelerate the remediation of PCP contaminated paddy soils.

Pentachlorophenol Sorption in the Cetyltrimethylammonium Bromide/Bentonite One-Step Process in Single and Multiple Solute Systems

The selective sorption of pentachlorophenol (PCP) in a multiple solute system provides the possibility of using the cetyltrimethylammonium bromide (CTMAB)/bentonite one-step process as a promising ...

The impact of solution chemistry of electrolyte on the sorption of pentachlorophenol and phenanthrene by natural hematite nanoparticles

Hematite nanoparticles (NPs) were studied as a sorbent for hydrophobic organic contaminants (OCs) under natural ambient conditions through specially designed contrasting solution chemistry of electrolyte. Ionizable pentachlorophenol (PCP) and non-ionizable phenanthrene (PHE) were selected as representative OCs. The sorption capacities of PCP and PHE were pH-dependent, and a larger amount of PCP was sorbed at pH values below its pKa (4.75). However, the PHE sorption capacity was higher at relatively high or low pHs (e.g. below 4.0 and above 10.0), possibly due to the larger available surface area of the hematite NPs, caused by the higher values of net charges and charge density. Changes in pH might thus affect the sorption of OCs by hematite NPs, through modification of the surface characteristics of the sorbent and the electronic properties of the sorbate molecules. The influence of different ionic strengths indicated that the amounts of PCP and PHE sorbed by hematite NPs decreased as a concentration function of different types of ions (e.g. Na+, K+, Mg2+ and Ca2+), with the underlying mechanism possibly being due to four interactions i.e. hydrogen-bonding, competitive sorption by ions in the ambient solution, screening effects and aggregation effects. The results confirmed that the surface chemistry of hematite NPs, the chemical properties of PCP and PHE, and solution chemistry (e.g. pH and ionic strength) of the electrolyte all played an important role in PCP and PHE sorption by hematite NPs. By comparison of both sorption capacity and ecologic advantages, our results suggested that natural hematite NPs would be more competitive and efficient for PCP and PHE sorption than engineered NPs. This finding increases our knowledge regarding the environmental function of natural NPs (such as hematite NPs) for OC remediation through manipulating their interfacial behavior.

Dechlorination of Pentachlorophenol by Palladium/Iron Nanoparticles Immobilized in a Membrane Synthesized by Sequential and Simultaneous Reduction of Trivalent Iron and Divalent Palladium Ions

Abstract Dechlorination of pentachlorophenol (PCP) by zero-valent iron (Fe0) and palladium (Pd)/iron (Fe) bimetallic nanoparticles (NPs) immobilized in nylon 6,6/PEG membranes was investigated at room temperature. Pd/Fe bimetallic NPs were synthesized by two different approaches, sequential and simultaneous reduction of trivalent iron (Fe3+) and divalent palladium (Pd2+) ions. Pd/Fe NPs prepared by simultaneous reduction showed a much smaller particle size, only 30 nm in average, and significantly higher reactivity toward PCP dechlorination than the other two materials. Almost 85% PCP removal within 45 min was qualified in terms of both phenol emergence and chlorine ion release. In contrast, dechlorination efficiency by Pd/Fe NPs immobilized by sequential reduction was insignificant. Iron oxides between Fe0 and Pd0 during the sequential reduction process impeded their effective contact, and enhanced PCP sorption on membranes. Spectra of X-ray photoelectron spectroscopy confirmed the existence of both Fe0 ...

Influence of humic acid on the sorption of pentachlorophenol by aged sediment amended with rice-straw biochar

Black carbon (BC), especially biochar, is a potential material for the remediation of hydrophobic organic compounds (HOCs) pollution in soils and sediments. Recent studies have reported that the adsorption capability of BC in sediment was reduced as time increased. It was hypothesised that this behaviour was caused by the presence of natural organic matter (NOM), but few systematic studies have examined the influence of NOM on the sorption ability of BC in sediment (S). The results of this study revealed that a humic acid (HA) coating changed the surface properties, blocked the micropores, and decreased the sorption capacity of rice-straw biochar (RBC) towards pentachlorophenol. With increasing aging time, the reductions in the sorption capacity of the S+RBC and S+HA+RBC systems occurred more rapidly than in the S+HA/RBC (HA-coated RBC) system, and the sorption curves became closer to that of the S+HA/RBC system, indicating that HA may play a primary role in reducing the sorption capacity of RBC in the sediment. With higher HA contents, the sorption capacity of the complex sediments was lower and decreased more rapidly.

Fixed-bed column studies of pentachlorophenol removal by use of alginate-encapsulated pillared clay microbeads

Columns were packed with two alginate/pillared clays microbeads (aluminium-pillared clay and surfactant-modified aluminium-pillared clay). Pentachlorophenol sorption performance was assessed under variable operating conditions: different bed heights, influent pentachlorophenol concentrations and flow rates. These conditions greatly influenced the breakthrough time/volume, the saturation time/volume and the uptake capacity. Higher values of experimental uptake capacities were obtained for the encapsulated surfactant-modified aluminium-pillared clay compared with the encapsulated aluminium-pillared clay, and the values were compared with those obtained with other low-cost sorbents. The experimental breakthrough curves were modelled using Bed Depth Service Time (BDST), Wolborska and Thomas models. Linear relationship was obtained for the BDST model, indicating the suitability of this model; bed capacity increased sharply with the introduction of CTAB in the inorgano-pillared clay. Wolborska model was applied only to the initial part of the curves. Thomas model was no doubt the most suitable description of the adsorption mechanisms for the entire breakthrough curves. Experimental and Thomas model-predicted equilibrium uptake capacities were in accordance.

Influences of pH, heavy metals and phosphate and their co-influences on the sorption of pentachlorophenol on cyanobacterial biomass

Influences of pH, two types of ions of transition metals (Cu2+, Cd2+), Na3PO4 and their co-influences on the sorption of pentachlorophenol (PCP) on cyanobacterial biomass derived from natural bloom were studied. Sorption of PCP significantly decreases with pH in the range of 3.25–9.00. Although sorption coefficient of ionized PCP is 8.51 times lower than that of neutral species, it is the dominant species at environmentally relevant pH and contributes more to the total sorption of PCP. In the presence of low concentration of Cu2+ (≤40 μmol L−1), sorption of PCP was much lower than that of the blank. However, it increased gradually with Cu2+, and overpassed the blank when concentration of Cu2+ was higher than 50 μmol L−1. Compared with the sole influence of pH, coexisted Cu2+ inhibited the sorption of PCP at pH of 3.25 and 4.35, but enhanced it in the pH range of 5.00–9.00. In the presence of Cd2+, sorption of PCP first increased then decreased rapidly and finally increased slightly again with Cd2+. Except for at pH of 9.00, sorption of PCP at other pH in the presence of Cd2+ was much lower than that solely affected by pH. In the presence of Na3PO4, sorption of PCP increased rapidly then maintained with Na3PO4. Under the influence of both Na3PO4 and pH, sorption of PCP at pH from 3.25 to 5.00 was lower than that solely affected by pH, while it increased with pH in the range of 5.00–9.00 and was higher than that solely affected by pH in the range of 6.00–9.00. Ion pairs of pentachlorophenolate-metal facilitated the sorption of PCP, which was largely dependent on pH illustrated by UV–visible and FTIR spectra. Speciations of metals and PCP and the stability constants of ion pairs of pentachlorophenolate-metal greatly affected the sorption. Ionic strength also played an important role for the sorption of PCP.

The sorption of pentachlorophenol by aged sediment supplemented with black carbon produced from rice straw and fly ash

Black carbon (BC) is a potential material for controlling hydrophobic organic contaminants in sediment because it has a high sorption capacity. In the present study, the sorption of pentachlorophenol (PCP) onto sediments supplemented with rice straw biochar (RC) and fly ash (FC) aged for different times and at temperatures were investigated. The sorption of PCP increased with increasing amounts of BC and decreased with aging time and storage temperature of the BC-supplemented sediments. The sorption of PCP onto RC-supplemented sediments was higher than those supplemented with FC regardless of whether or not BCs were aged in sediments. For aged sediments containing 2% BCs, the sorption capacity was 9.15- and 2.87-fold higher than that of FC when supplemented with RC aged at 25 and 45°C, respectively. Therefore, biochar is better than fly ash for controlling organic pollutants even when the RC was present in sediment for a long time.

Interactions of synthetic Fe(II)–Fe(III) green rusts with pentachlorophenol under various experimental conditions

Sorption of pentachlorophenol (PCP) to three different green rusts (GRs) was studied versus time and initial PCP concentration at neutral pH. A competitive adsorption occurred when salicylate or silicate was present in the reaction medium. The monitoring of chloride formation and PCP byproducts indicated the absence of any possible reductive pathway in the PCP removal. All solid characterization showed that the PCP sorption in the presence or absence of foreign ligands did not alter the GR structure. Addition of nitrate (weak oxidant) involved a gradual release of PCP in solution from the sorbent solid. This is probably due to the oxidative transformation of GR into magnetite that sorbs less PCP. However, reaction with a strong oxidant (H 2O 2) involved both dechlorination and mineralization of PCP via oxidation reaction. HPLC and ion chromatography analysis, TOC and dissolved iron measurements showed that PCP had been degraded by heterogeneous Fenton-like reaction. Both X-ray diffraction analysis and Raman spectroscopy showed that the oxidation of GR may lead to magnetite (Fe 3O 4) or goethite (α-FeOOH), depending on the oxidant type. As green rusts have considerable potential in environmental applications, the influence of naturally occurring ligands and/or oxidants on the reactivity of green rusts should be considered.