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.

In this study, residues of passion fruit skin were examined as biosorbent materials, evaluating their capacity to adsorb lead(II) ions in in natura skin (SK-N) and two modified skins, with NaOH (SK-S) and with NaOH and citric acid (SK-SCA). The biomass characterization was done through Fourier transform infrared spectroscopy which confirmed the chemical modification by a peak at 1,730 cm⁻¹. Also, scanning electron microscopy analyses were done, where the increase of residue roughness was observed after the modification. And finally, the values of point of zero charge were determined and were lower than 5.5 for all residues. In the experiments of adsorption in function of pH, it was verified that after pH 4, the adsorbed amount was practically constant. Regarding the necessary time to reach equilibrium, the value that was found was approximately 170 min, and kinetics followed the behavior described by the pseudo-second-order equation. The maximum adsorption capacity was 204 mg g⁻¹ for the SK-SCA biomass. The residues followed Langmuir adsorption model. Through thermodynamic parameters, it was verified that adsorption occurs spontaneously due to the negative values of Gibbs' energy. Moreover, desorption studies showed that adsorbed ions may be recovered in two cycles. Thus, due to the high adsorption capacity of lead ions, passion fruit skin can be utilized in filters to retain this metal in the future.

Although Cd concentrations in uncontaminated soils are usually low, pollution of soils by Cd from different sources of contamination pose problems. The application of soil amendments to increase plant production has been used as a viable alternative for recovery of soils contaminated with Cd. However, emphasis needs to be placed on the nature of Cd sorption processes in order that the amendments can be managed appropriately. A range of materials including vermicompost, sugarcane filter cake, palm kernel pie, lime, phosphate rock, and zeolite were used for the sorption studies. Total and nonspecific Cd sorption was estimated by batch experiments, and specific sorption was obtained by the difference between the former and the latter. Best adsorbents for specific Cd sorption from soil amendments were lime and zeolite. Langmuir adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R ² values from 0.80 to 0.99. The maximum adsorption capacity of Cd(II) was higher for mineral amendments than for organic amendments and ranged from 0.89 to 10.86 g kg⁻¹. The small value (0.08 L mg⁻¹) of the constant related to the energy of adsorption indicated that Cd was bound weakly to the palm kernel pie. Thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous. The values of separation factor, R L, which has been used to predict affinity between adsorbate and adsorbent were between 0 and 1, indicating that sorption was very favorable for Cd(II).

Pollution by heavy metals (Co, Cu, Ni, Pb, Sb and Zn), Ra-226 and U was studied in eight profiles (1.0-1.8 m deep) in the floodplain sediments of the Ploucnice River, the Czech Republic. The element concentrations were processed by establishing local geochemical background functions from non-polluted overbank fines yet not affected by reductimorphic processes and a subsequent calculation of enrichment factors in the polluted strata. In the case of Cu and Ni, the geogenic variability of the watershed (Cretaceous marine sediments and Cenozoic volcanics and their weathering products) was successfully handled using different background functions in two parts of the studied area, which allowed us to decipher the anthropogenic and natural portions of the heavy metals and hence evaluate the history of pollution. The upper course of the river drains an extensive area of so-called chemical mining (underground acid leaching of low-grade U-bearing sediments) and hydrometallurgical processing in Straz pod Ralskem that started in the late 1960s and operated without waste-processing plants up to 1989. The river system has consequently been impacted by U and gamma-emitting Ra-226 and obviously also by divalent heavy metals (Co, Ni, Zn). In the entire study area, that pollution was preceded by increasing levels of Cu, Pb and Sb and by the Pb-206/Pb-207 ratio decreasing from 1.20 towards 1.17, which had started earlier in the twentieth century before the U mining. That pre-mining pollution can be attributed to diffuse anthropogenic activities of regional or continental importance. The most recent Pb-206/Pb-207 ratio in the Ploucnice alluvium coincides with that of peatbog profiles on the borders of the Czech Republic, showing the usefulness of floodplains as pollution archives of widespread regional to continental pollution signals.

Anionic polyacrylamide (PAM) is a linear, water-soluble anionic polymer that is widely used for erosion control and water quality protection. There has been an issue whether this formulation could possibly have negative effects on soil microbial diversity by altering microbial binding to soil particles or to one another and thus restricting their mobility and role in carbon and nutrient cycling. We conducted an 8-year study annually applying ultra-high rates of PAM to soil and then monitored impacts on soil bacterial diversity. In July and August, we measured active soil bacterial and fungal biomass and microbial diversity in soils receiving 0 (control), 2,691, and 5,382 kg active ingredient PAM ha⁻¹. Active microbial biomass in soil was 19–33 % greater in the untreated control than soil treated with 2,691 or 5,382 kg of active ingredient PAM ha⁻¹. Active bacterial biomass in soil was 21–31 % greater in the control treatment than in soil treated with 2,691 or 5,382 kg of active ingredient PAM ha⁻¹ in August, but not July. Active fungal biomass in soils was 38–50 % greater in the control treatment than soil treated with 2,691 or 5,382 kg of active ingredient PAM ha⁻¹ in July, but not August. Molecular methods were used to access the bacterial diversity, richness, and evenness in an agricultural soil that received 0 (control), 2,691, and 5,382 kg of active ingredient PAM ha⁻¹. We found that although soil receiving these massive PAM application rates and prolonged exposure may reduce active bacterial and fungal biomass, PAM application did not substantially or consistently affect bacterial structural diversity, richness, or evenness in this agricultural soil.

Cadmium (Cd) is a non-essential heavy metal, considered a high-priority pollutant. It occurs naturally in the environment but anthropogenic activities may enhance its presence, with consequences to the biota. Metal research has been focused in the crustaceans but knowledge on estuarine isopods has been lacking. The aim of this study was to assess the bioconcentration kinetics in the estuarine key species Cyathura carinata. This isopod was exposed to different treatments of Cd, through aqueous pathway: control, low (I), medium (II) and very high (III) concentrations during 14 days, being collected along seven sampling times. After the end of the exposure period, the mean uptake rates were 0.023, 0.040 and 0.634 μg g⁻¹ day⁻¹ for each treatment, respectively. Statistical differences in accumulated Cd were recorded between treatments, except between control and treatment I. A linear pattern of accumulation through time was detected for all the concentrations, being most perceptible in the treatment III, where measured Cd in C. carinata’s tissues was significantly different between all the sampling times. Cd accumulation in treatments I and II was not so pronounced, being only noticeable at the end of the exposure period. In these treatments, final concentrations were two and almost four times greater than control, respectively, while in treatment III Cd concentration increased 60 times. Survival did not seem to be affected in the various treatments, suggesting the existence of a strategy for preventing toxic activity of Cd that needs further investigation.

Poised to gain insight into nitrate adsorption and removal processes from water through employment of modified surfaces, a well-defined inorganic manganese species was used in connection with hydrophobic mesoporous silica. To this end, the surface of hydrophobic mesoporous silica was modified by coating silica with a manganese oxychloride (Mn₈O₁₀Cl₃) nanoparticle layer. A sol–gel method was utilized for the synthesis of hydrophobic silica, using tetraethyl orthosilicate–methyl triethoxysilane (TEOS–MTES) as precursors. Subsequent coating with Mn₈O₁₀Cl₃ took place by mixing MnCl₂ and NaOH with hydrophobic silica. Physicochemical characterization of the Mn₈O₁₀Cl₃-coated silica was carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ sorption. The achieved surface modification reduced remarkably the specific surface area by 80.7 % and influenced the ability of nitrates to adsorb on Mn-modified silica. Nitrate adsorption kinetics on Mn₈O₁₀Cl₃-coated silica was studied by a batch reactor. Process parameters including pH, temperature, and initial nitrate concentration were examined thoroughly. The experimental adsorption data were fitted satisfactorily through Langmuir isotherm equations and were found to be well-represented by a pseudo-second-order kinetic model. The collective data emphasize the significance of well-defined inorganic manganese phases, coating hydrophobic silica, in optimally influencing water decontamination from pollutant nitrates.

Two methods to measure mercury concentration in soil are compared, and their compliance with international standards is determined: cold vapour atomic absorption spectrometry and thermal decomposition, amalgamation and atomic absorption spectrophotometry. The detection limit, quantification limit and uncertainty of these two analytical methods were evaluated and compared. The results indicated that thermal decomposition, amalgamation and atomic absorption spectrophotometry had a lower quantification limit and uncertainty than cold vapour atomic absorption spectrometry (quantification limit, 0.27 vs. 0.63 mg kg⁻¹; expanded uncertainty, 9.30 % vs. 10.8 %, respectively). Thermal decomposition, amalgamation and atomic absorption spectrophotometry allowed the determination of the base values for the concentration of mercury in soil recommended by international standards, achieving a lower detection limit than cold vapour atomic absorption spectrometry under the study conditions. In addition, thermal decomposition, amalgamation and atomic absorption spectrophotometry represent a more environmentally friendly alternative for mercury determination because this method uses fewer reagents and therefore generates less waste.

Biochar has great potential as a soil amendment to immobilize heavy metals, thereby reducing their bioavailability. In this study, biochars derived from chicken manure and green waste were compared with commercial activated carbon (AC) and laboratory produced black carbon (BC) for the sorption of Pb and Cd. Sorption kinetics and equilibrium sorption isotherms for Pb and Cd were obtained for the char materials and the data were fitted to kinetic and sorption isotherm models. Chicken manure-derived biochar (CM) showed the highest sorption capacity for both Pb and Cd, and the Pb sorption by biochars was higher than the Cd sorption because of the precipitation of Pb with various ions released from the biochars such as carbonate, phosphate, and sulfate. The sorption data for both Pb and Cd were better represented by the pseudo-second order kinetic model than the pseudo-first order kinetic model, which indicates chemical sorption between biochar and metals. For the isotherm studies, char materials was mixed with various amount of Pb or Cd solutions and the remaining metal concentration was measured. The equilibrium sorption data followed a Langmuir isotherm with a maximum sorption capacity of 6.8-11 and 1.7-8.0 mg/g by biochars for Pb and Cd, respectively. Furthermore, CM immobilized Pb and Cd up to 93.5 and 88.4 %, respectively, while BC was not effective in the immobilization of Pb in soil. Overall, the sorption experiments in solution and the immobilization experiment in soil showed that biochars are more effective than AC in the sorption of Pb and Cd, and that they have the potential to be used as a soil amendment to remediate metal-contaminated soil. © 2013 Springer Science+Business Media Dordrecht.

A comprehensive investigation of polybromodiphenyl ethers (PBDEs) in wastewater was conducted in the second largest international metroplex area along the U.S. and Mexico (MX) border. Concentrations of PBDEs in wastewater and sludge were measured in four wastewater treatment plants (WWTPs) in El Paso, Texas and two WWTPs in Cd. Juarez, Chihuahua, MX. A green approach in sample preparation technique, called stir bar sorptive extraction (SBSE) coupled with thermal desorption and gas chromatography and mass spectrometry, was used which requires minimum amount of organic solvents and has good sensitivity at nanogram-per-liter levels for wastewater samples and nanograms per gram for waste sludge solids. Concentrations of PBDEs ranged from 30.2 to 342 ng L⁻¹ in wastewater influents, from not detected to 209 ng L⁻¹ in effluents, and from not detected to 1,303 ng g⁻¹ in sludge. Among 27 PBDEs studied, BDE-47, BDE-99, and BDE-100 were the most commonly detected congeners in all samples. Further evaluation showed that secondary and tertiary treatments are highly effective at removing PBDEs from wastewater with percent removals ranging from 84 % to 100 %, while advanced primary treatment only removed 41–73 % of PBDEs. As a complement, the ambient air temperature change on PBDEs concentrations was evaluated finding that this factor did not have an influence on the PBDEs concentrations in WWTPs. The incomplete removal of PBDEs in WWTPs implicates a potential impact on the environmental and public health as a result of the continuous release of PBDEs from the WWTPs to the Rio Grande River and irrigation canals.