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.

Thorium(IV) biosorption is investigated by citric acid treated mangrove endophytic fungus Fussarium sp. #ZZF51 (CA-ZZF51) from South China Sea. The biosorption process was optimized at pH 4.5, equilibrium time 90min, initial thorium(IV) concentration 50mgL−1 and adsorbent dose 0.6gL−1 with 90.87% of removal efficiency and 75.47mgg−1 of adsorption capacity, which is obviously greater than that (11.35mgg−1) of the untreated fungus Fussarium sp. #ZZF51 for thorium(IV) biosorption under the condition of optimization. The experimental data are analyzed by using isotherm and kinetic models. Kinetic data follow the pseudo-second-order model and equilibrium data agree very well with the Langmuir model. In addition, FTIR analysis indicates that hydroxyl, amino, and carbonyl groups act as the important roles in the adsorption process.

Adsorption potentials of native and amine-modified plant biomass of Alyssum caricum for the removal of Reactive Green 19 (RG-19) and Reactive Red 2 (RR-2) dyes from aqueous solutions were studied. The adsorbents were characterized before and after modification process using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and potentiometric titration analysis. Modification of the surface of A. caricum biomass with hexamethylenediamine (HMDA) showed an increase of 1.18-fold in its surface area. Batch studies illustrated that dye adsorption were highly dependent on different process variables, pH, initial dye concentration of solution, adsorbent dosage, and temperature. The maximum adsorption capacities of the native and amine-modified adsorbents were 27.6 and 63.4 mg/g adsorbent for RG-19 dye and 16.5 and 36.8 mg/g adsorbent for RR-2 dye, respectively. The adsorption of both dyes on the native and amine-modified plant biomass correlated well with the Langmuir and Temkin isotherm equations as compared to Freundlich and D-R equations. The calculated thermodynamic parameters for both native and amine-modified adsorbents showed that the adsorption was feasible, spontaneous, and exothermic. The information gained from these studies was expected to indicate whether native and amine-modified adsorbents can have potential to be used for the removal of other dyes from wastewaters. © 2013 Springer Science+Business Media Dordrecht.

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.

Imperata cylindrica leaf was used as raw material to prepare two different adsorbents through chemical modification by using sulfuric acid and phosphoric acid. These two adsorbents, sulfuric acid-modified I. cylindrica leaf-based adsorbent (SIC) and phosphoric acid-modified I. cylindrica leaf-based adsorbent (PIC), were used to adsorb nickel ions (Ni²⁺) from aqueous solutions. The I. cylindrica leaf-based adsorbent and modified I. cylindrica leaf-based adsorbents were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Different operational parameters such as initial solution pH, adsorbent size, adsorbent dosage, initial Ni²⁺ ion concentration, and temperature were studied. The adsorption isotherm and the adsorption kinetics were studied systematically. Based on the FT-IR spectrum before and after adsorption of Ni²⁺ ions, the adsorption mechanism involved both ion exchange and complexation between Ni²⁺ ions and functional groups on the surface of adsorbents. There was no sulfur and phosphorus detected in the aqueous solutions after adsorption. Therefore, SIC and PIC are effective in adsorbing Ni²⁺ ions and will not cause secondary pollution to the environment.

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).

Acid mine drainage (AMD) has long been a significant environmental problem that impairs water resources in historic or current mining industries throughout the world. One of the methods using passive treatment system at low cost to remove metals from solution involves the use of clays. The ability of three different adsorbents (montmorillonite K-10, bentonite (NT-25), and hydrotalcite (HT)) to remove Fe and Mn from aqueous solutions and acid mine drainage samples has been studied at different optimized conditions such as pH, amount of adsorbent and contact time. Flame atomic absorption spectrometer (FAAS) was used for measuring Fe and Mn concentrations. Langmuir and Freundlich isotherms were applied and isotherm coefficients were computed. A kinectic study was also developed for HT using the first order, second order and intraparticle diffusion models. A great amount of clay (more than 100 mg) and also contact times higher than 60 min had also no influence in the adsorption capacity for all adsorbents. HT was found to be the best among the studied clays removing more than 90 % of Fe and Mn for all AMD samples investigated. Moreover, the maximum adsorption capacity was 63.7 mg Mn g⁻¹ HT and 666.7 mg Fe g⁻¹ HT.

Bottom slag and sewage sludge discharged from municipal solid waste incineration and sewage treatment plants were co-sintered for use as a cost-effective adsorbent for phosphate removal from aqueous solutions. The Langmuir isotherm model (which gives a better description of phosphate sorption than the Freundlich model) was adopted to describe the action of the synthesized adsorbent and also for phosphate sorption by either zeolite or ironstone. The model showed that the maximum sorption capacity of the synthesized adsorbent (27,030 mg kg-1) was 38.2 greater than for zeolite and 70.6 times greater than for ironstone. Desorption of phosphate from the synthesized adsorbent at different initial concentrations was about 4.98 %, which was several times lower than for zeolite. The phosphate removal capacity of the synthesized adsorbent remained constant for solution pH values ranging from 3 to 10, which was an improvement on the capacity of the other two adsorbents; its buffering capacity was also superior. The immobilization of phosphate on the synthesized adsorbent might be attributed mainly to complexation with Fe, Al, and Ca ions. Heavy metal ion concentrations in the leachate of the synthesized adsorbent were negligible. © 2013 Springer Science+Business Media Dordrecht.

Adsorption by low-cost adsorbents and biosorbents is recognized as an effective and economic method for low-concentration heavy metal. The purpose of this study was to investigate the possibility of the utilization of N,N′-bis(2, 5-dihydroxybenzylidene)-1, 4-diaminobenzene (DHDB)-immobilized sporopollenin (Schiff base-immobilized sporopollenin, Sp-DHDB) as a sorbent for removal of lead (II) ion from aqueous solution. The effects of different parameters (such as sorbate concentration, sorbent dosage, and pH of the medium) were investigated by differential pulse anodic stripping voltammetry (DPASV) technique. The experimental data were analyzed by the Freundlich, Langmuir, and Dubinin–Radushkevich (D–R) isotherms. Equilibrium data fitted well with the Freundlich model and the procedure developed was successfully applied for the removal of lead ions in aqueous solutions. This investigation reveals a new, simple, environmentally friendly, and cost-effective method for the removal of lead ions from aqueous solutions by a new Sp-DHDB material.

The removal of lead (II) and iron (III) from aqueous solutions using empty fruit bunch (EFB), oil palm leaves (OPL), oil palm frond (OPF), and oil palm bark (OPB) as biosorbents was investigated. The biosorbents were characterized through scanning electron microscopy, Brunauer–Emmett–Teller analysis, and Fourier transform infrared spectroscopy. Variables such as pH (2–12), biosorbent particle size (200–1,400 μm), adsorbent dosage (0.25–1.75 g/l), and agitation time (5–80 min) were investigated. The suitable pH range, particle size, adsorbent dosage, and agitation time for the removal of both metals were 5 to 6, 200 μm, 1 g/l, and 40 min, respectively. Under optimum conditions, OPB showed the highest adsorption efficiency of 80 % and 78 % for lead and iron, respectively. The adsorption equilibrium data were fitted to three adsorption isotherm models. The Langmuir isotherm showed the best result for both metals. The kinetics of the biosorption process was analyzed using pseudo-first-order and pseudo-second-order models. The latter showed a better fit for both metals. OPB biomass introduced the lowest chemical oxygen demand into the treated solution, with an average amount of 32.9 mg/l.