The in situ use of carbon amendments such as activated carbon (AC) and biochar to minimize the bioavailability of organic contaminants is gaining in popularity. In the first in situ experiment conducted at a Canadian PCB-contaminated Brownfield site, GAC and two types of biochar were statistically equal at reducing PCB uptake into plants. PCB concentrations in Cucurbita pepo root tissue were reduced by 74%, 72% and 64%, with the addition of 2.8% GAC, Burt's biochar and BlueLeaf biochar, respectively. A complementary greenhouse study which included a bioaccumulation study of Eisenia fetida (earthworm), found mechanically mixing carbon amendments with PCB-contaminated soil (i.e. 24 h at 30 rpm) resulted in shoot, root and worm PCB concentrations 66%, 59% and 39% lower than in the manually mixed treatments (i.e. with a spade and bucket). Therefore, studies which mechanically mix carbon amendments with contaminated soil may over-estimate the short-term potential to reduce PCB bioavailability.

The removal of tributyltin (TBT) from artificial seawater using nZnO, activated carbon and nZnO/activated carbon composite was systematically studied. The equilibrium and kinetics of adsorption were investigated in a batch adsorption system. Equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models. Pseudo first- and second-order, Elovich, fractional power and intraparticle diffusion models were applied to test the kinetic data. Thermodynamic parameters such as ΔG°, ΔS° and ΔH° were also calculated to understand the mechanisms of adsorption. Optimal conditions for the adsorption of TBT from artificial seawater were then applied to TBT removal from natural seawater. A higher removal efficiency of TBT (>99%) was obtained for the nZnO/activated carbon composite material and for activated carbon but not for nZnO.

This paper demonstrates an approach to reducing acute toxicity in marine sediments using adsorbent parcels. Acute toxicity tests were carried using the marine amphipod Corophium volutator. Marine sediments were spiked with two know contaminants tributyltin and naphthalene and then treated with adsorbent parcels containing either amberlite XAD4 or activated carbon. Results showed that both types of adsorbent parcels were effective in reducing acute toxicity, not only within spiked sediments containing naphthalene and/or tributyltin, but also in an environmental field samples form an expected contaminated site. Adsorbent parcels such as these could provide a practical approach to remediate areas of contaminated sediment within marine environments. Furthermore adsorbents can be used as an identification tool for problematic contaminants using a toxicity identification evaluation approach.

The impact of three commercially available nanoparticles (NPs) on trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) was investigated. TCE adsorption isotherm and column breakthrough experiments were conducted in the presence and absence of silicon dioxide, titanium dioxide, and iron oxide nanoparticles. A rapid small-scale column test (RSSCT) was assessed for its ability to predict TCE adsorption in pilot-scale GAC in the presence and absence of NPs. Zeta potential of the three NPs and the GAC were measured. Particle size distribution of the NP dispersions was analyzed as a function of time. The surface area and the pore size distribution of the virgin and the exhausted GAC were obtained along with transmission electron microscopy and Fourier transform infrared spectroscopy analysis. The effect of NPs was found to be a function of their zeta potential, concentration, and particle size distribution. Due to their electrical charge, NPs attached to the GAC and blocked the pores and thus reduced the access to the internal pore structure. However, due to the fast adsorption kinetics of TCE, no effect from the three NPs was observed in the isotherm and kinetic studies. The RSSCT, on the other hand, accurately predicted the pilot-column TCE breakthrough in the presence of NPs.

The remediation of tributyltin (TBT) by adsorption onto nFeO, activated carbon and nFeO/activated carbon composite material as a function of adsorbent dose, contact time, pH, stirring speed, initial TBT concentration and temperature was studied. The effect of temperature on kinetics and equilibrium of TBT sorption on the precursors and the composite was thoroughly examined. The adsorption kinetics is well fitted using a pseudo-second-order kinetic model, and the adsorption isotherm data of nFeO, activated carbon could be described by the Freundlich isotherm model whereas nFeO/activated carbon composite could be described by the Freundlich and Dubinin-Radushkevich isotherm models. Thermodynamic parameters (i.e. change in the free energy (∆ G°), the enthalpy (∆ H°) and the entropy (∆ S°)) were also evaluated. The overall adsorption process was endothermic and spontaneous in nature. The results obtained also showed that 99.9, 99.7 and 80.1 % TBT were removed from contaminated natural seawater by nFeO/activated carbon composite, activated carbon and nFeO, respectively.

A laboratory-scale study was conducted to determine the removal efficiencies of nine contaminants from a tannery wastewater using a number of physicochemical processes. Coagulation–flocculation using bittern as coagulant, oxidation-utilizing ozone, and adsorption using activated carbon were applied separately and in different sequences. Jar tests were utilized to conduct the experimental work. Except for arsenic, the highest removal efficiencies were recorded when coagulation/flocculation was conducted on the alkalized samples using a bittern dose of 5 mL/L. Activated carbon adsorption improved removal efficiencies of several contaminants. The coagulation/flocculation–adsorption sequence using the optimum dose of 5 mL/L of bittern resulted in high removal efficiencies for total suspended solids (TSS) (97 % ± 1), apparent color (100 % ± 0), turbidity (97 % ± 1), total nitrogen (86 % ± 1), and chromium (100 % ± 0). On the other hand, the same sequence resulted in moderate removal efficiencies for chemical oxygen demand (COD) (72 % ± 7) and total phosphorus (74 % ± 5) and relatively low removals for biochemical oxygen demand (BOD) (55 % ± 10) and arsenic (42 % ± 14). The removal efficiencies for the different tested sequences demonstrated that each sequence did improve the removal efficiencies for most of the parameters tested and consequently, the quality of tannery effluent. However, no single optimum sequence was capable of attaining high removal efficiencies for all nine parameters.

The adsorption mechanism of Ni(II) and Zn(II) onto activated carbon fiber (ACF) cloth and felt plain and oxidized was investigated in this work. The adsorption equilibrium data were obtained in a batch adsorber. The concentration of acidic and basic sites on the ACFS was determined by an acid-base titration method. The experimental adsorption equilibrium data were interpreted with the Redlich-Peterson isotherm, which fitted the data reasonably well. The ACF was oxidized with HNO3 solution and the concentration of acidic sites increased during oxidation, whereas that of the basic sites diminished. The adsorption capacity of the oxidized ACF was higher than that of the plain ACF because the oxidation of ACF formed more acidic sites on the surface where the metal cations can be adsorbed. The adsorption capacity of the plain and oxidized ACFs was linearly dependent upon the concentration of carboxylic sites. The adsorption of Ni(II) and Zn(II) on the ACFs was due to both electrostatic interactions and cation-π interactions. The contribution of ion exchange to the overall adsorption of Zn(II) and Ni(II) on ACFs was less than 3.3 % and can be considered negligible. © 2013 Springer Science+Business Media Dordrecht.

The competitive adsorption of organic pollutants—phenol, aniline and n-heptane—from biologically treated coking wastewater on powdered activated carbon (PAC) was studied. Firstly, batch adsorption experiments of coking wastewater were conducted to investigate the effect of pH and temperature on their adsorption. Results showed that long-chain alkanes, benzoic, halogenated and phenolic compounds were adsorbed well under acidic condition, while amines were adsorbed well under alkaline condition; maximum co-adsorption amount of all kinds of organic compounds occurred at around pH 5. Then, Lagergren kinetic model and pseudo-second-order kinetic model were used to describe the adsorption process of phenol and aniline on PAC. The data were fitted very well with pseudo-second-order kinetics, and the adsorption capacity decreased with an increase in temperature, belonging to Freundlich multi-layer physical adsorption. The adsorption speed and capacity of phenol were superior to aniline in unitary and binary solution. The adsorption amount of n-heptane decreased by 26.6 % from ternary competitive absorption system of phenol, aniline and n-heptane compared with that in unitary solutions, which showed that phenol and aniline caused spatial adsorption steric hindrance to n-heptane.

This study aimed to evaluate the efficacy of using the byproduct of Moringa oleifera Lam. seeds as an adsorbent for removal of cadmium (Cd) from contaminated water. The material characterization was performed by scanning electron microscopy, infrared spectroscopy, and point of zero charge. The effects of the adsorbent mass, solution pH, contact time, and temperature were evaluated. In the preliminary studies, the mass of adsorbent (200–1200 mg) and pH conditions (5.0, 6.0, and 7.0) were varied. The time studies were performed at 20–180 min and the temperature studies at the range of 25–65 °C. The optimal conditions of adsorption obtained were 400 mg of adsorbent mass, 7.0 pH, and 160 min contact time with the adsorbent. The isotherms of adsorption were linearized according to Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) models. The results showed better fit by the Freundlich and D-R models for Cd adsorption, describing a multilayer adsorption and, according to the value of the sorption energy (E), it has chemical nature. The maximum capacity of adsorption (Q ₘ) obtained was 7.864 mg g⁻¹. For a comparative study, the activated carbon (P.A.) was used applying the same optimal conditions used in the adsorption isotherms and desorption process for the biosorbent, obtaining a Q ₘ as 32.884 mg g⁻¹. The average desorption percentage showed that adsorbents have strong interaction with the metal. Based on these results, it was concluded that the biosorbent was effective in remediation of solutions containing Cd and thus the use of this alternative material is a viable option, since it has low cost and it is a byproduct which has not undergone previous treatment.

In this study, arsenate removal by apricot stone-based activated carbon (IAC) modified with iron (oxy-hydr)oxides was carried out. For this purpose, hybrid adsorbents based on Fe²⁺-loaded activated carbon (IAC–Fe(II)) and Fe³⁺-loaded activated carbon (IAC–Fe(III)) were synthesized by precipitation method. A three-level, three-factor Box–Behnken experimental design combined with response surface methodology (RSM) was employed to find the optimum combination of process parameters for maximizing the As(V) adsorption capacity of activated carbon-based iron-containing hybrid adsorbent. Three important operation parameters, namely, initial pH of solution (3.0–7.0), temperature (25–65 °C), and initial As(V) concentration (0.5–8.5 mg L⁻¹), were chosen as the independent variables, while the As(V) adsorption capacities of hybrid adsorbents were designated as dependent variables. Lack of fit test showed that the quadratic model provided the best fit to experimental data for both adsorbents with the highest coefficients of determination (R ²), adjusted R ², and p-values for lack of fit. The standardized effects of the independent variables and their interactions were tested by analysis of variance and Pareto chart. The model F-values (F IAC–Fₑ₍II₎=330.39 and F IAC–Fₑ₍III₎=36.19) and R ² values (R ² IAC–Fₑ₍II₎=0.9977 and R ² IAC–Fₑ₍III₎=0.9789) of second-order polynomial regression equations indicated the significance of the regression models. Optimum process conditions for As(V) adsorption onto IAC–Fe(II) were 63.68 °C, pH 3.10, and 8.4 mg L⁻¹ initial arsenic concentration, while 25.22 °C, pH 3.07, and 8.28 mg L⁻¹ initial As(V) concentration were found to be optimum conditions for IAC–Fe(III).