Optimization of Pt(II) and Pt(IV) Adsorption from a Water Solution on Biochar Originating from Honeycomb Biomass

Novel CO2- and H3PO4-modified biochars were successfully synthesized from raw honeycomb biomass. They were characterized via several instrumental techniques. The optimal Pt(II) and Pt(IV) adsorption onto the studied biochars was reached for the initial pH of 1.5 and a contact time of 5 min (Pt(II)) and 24-48 h (Pt(IV)). The highest static adsorption capacities for Pt(II) and Pt(IV) were obtained for the H3PO4-modified biochar: 47 mg g-1 and 35 mg g-1, respectively. The Freundlich model described the Pt(II) adsorption isotherms onto both materials and the Pt(IV) adsorption isotherm onto the CO2-activated material, and the Langmuir model was the best fitted to the Pt(IV) adsorption isotherm onto the H3PO4-activated biochar. The best medium for the quantitative desorption of the Pt form from the H3PO4-modified biochar was 1 mol L-1 thiourea in 1 mol L-1 HCl. The adsorption mechanism of both the studied ions onto the synthesized H3PO4-modified biochar was complex and should be further investigated. The H3PO4-modified biochar was successfully applied for the first time for Pt(IV) removal from a spent automotive catalyst leaching solution.

Diclofenac-Impregnated Mesoporous Carbon-Based Electrode Material for the Analysis of the Arsenic Drug Roxarsone

This paper describes a novel electrode material, diclofenac-impregnated mesoporous carbon modified with a cationic surfactant, cetyltrimethylammonium bromide (DF-CMK-3/CTAB), for ultratrace analysis of the arsenic drug roxarsone (ROX). DF-CMK-3 amorphous carbon is a material with a high specific surface area and well-defined, hexagonally ordered, thin mesopores. The functional groups attached to the carbonaceous surface, such as chromene and pyron-like oxygen groups, lactam, and aromatic carbon rings, have the basic character and they can donate electrons. Modification of DF-CMK-3 with a CTAB layer significantly increases the analytical signal due to electrostatic interactions between the cationic surfactant and the anion form of ROX in the acidic medium. The voltammetric procedure at the glassy carbon sensor modified with DF-CMK-3/CTAB exhibited excellent sensitivity (limit of detection of 9.6 × 10-11 M) with a wide range of linearity from 5.0 × 10-10 to 1.0 × 10-4 M. Analysis of real samples (treated municipal wastewater and river water) showed recoveries from 96 to 102% without applying the complicated sample pretreatment step. The sensor demonstrated excellent sensitivity in the analysis of the arsenic drug ROX in the presence of interferences in environmental water samples.

Modified Mesoporous Carbon Material (Pb-N-CMK-3) Obtained by a Hard-Templating Route, Dicyandiamide Impregnation and Electrochemical Lead Particles Deposition as an Electrode Material for the U(VI) Ultratrace Determination

In this paper, a dicyandiamide-impregnated mesoporous carbon (N-CMK-3), electrochemically modified in situ with lead film (Pb-N-CMK-3), was tested as an electrode material for U(VI) ultratrace determination. The prepared carbon material was characterized by XRD, SEM-EDX, Raman, FT-IR, XPS analysis and nitrogen sorption measurements. The changes of electrochemical properties of glassy carbon electrodes (GCE) after the N-CMK-3 and Pb-N-CMK-3 modification were studied using CV and EIS methods. The modification of the GCE surface by the N-CMK-3 material and Pb film increases the electroactive area of the electrode and decreases the charge transfer residence and is likely responsible for the electrochemical improvement of the U(VI) analytical signal. Using square-wave adsorptive stripping voltammetry (SWAdSV), two linear calibration ranges extending from 0.05 to 1.0 nM and from 1.0 to 10.0 nM were observed, coupled with the detection and quantification limits of 0.014 and 0.047 nM, respectively. The Pb-N-CMK-3/GCE was successfully applied for U(VI) determination in reference materials (estuarine water SLEW-3 and trace elements in natural water SRM 1640a).

The effect of pH and ageing on the fate of CuO and ZnO nanoparticles in soils

The objective of this study was to evaluate the fractionation of ZnO and CuO engineered nanoparticles (ENPs) in soils with a pH adjusted to 4.0, 6.5, and 9.0 after 1 day and 30 days of incubation. Based on the multi-stage extraction, 5 fractions of metals were determined. Moreover, the effect of ENPs on the activity of acid, neutral and alkaline phosphatase was determined. The results of the study revealed that pH had a dominant effect on the metal participation in soils. The levels of those fractions of metals differed between nano-ZnO and nano-CuO, which could have resulted from differences in the dissolution of the ENPs. After 1 day, the concentration of Zn²⁺ (0.02-7.4 mg L^-1) was 10 times higher than that of Cu²⁺. The metal fractionation in soil treated with ENPs and metal salts may also confirm the role of ENP dissolution. The concentration of potentially bioavailable fraction of Zn increased with a drop in pH. At a 4 pH concentration of Zn in the treatment with nano-ZnO and ZnCl₂ was at a similar level (42.1-45 mg kg^-1), whereas the addition of nano-CuO resulted in a lower content of Cu (24.7 mg kg^-1) than CuCl₂ (36.5 mg kg^-1). On the other hand, the concentration of fraction exchangeable of both metals in the alkaline soil did not exceed the level of 5.0 mg kg^-1. Sample incubation time was especially important for metal participation in samples with a pH of 6.5. The greatest differentiation of metal fractionation between the soils was also noted at a pH of 6.5, which could also have been a result of other properties of the soils. The strong effect of pH on the lability of ENPs in soils confirmed a need to trace the fate of ENPs in extreme soil conditions as well as in changing environment.

Tailoring Surface Chemistry of Sugar-Derived Ordered Mesoporous Carbons Towards Efficient Removal of Diclofenac From Aquatic Environments

Ordered mesoporous carbon (CMK-3), obtained from an abundant natural source, sugar, was thermochemically modified with dicyandiamide and thiourea as well as by classical oxidization with hydrogen peroxide to introduce specific surface groups. Thermochemical modifications resulted in carbon with almost unchanged porosity and altered surface chemistry while porosity of H₂O₂-treated carbon was seriously deteriorated. The obtained carbons were tested as sorbents of diclofenac, considered as one of the emerging water contaminants. Changes in porosity and surface chemistry of modified carbons resulted in significant differences with regard to the uptake of diclofenac. Dicyandiamide-modified carbon showed highest uptake of drugs, reaching 241 mg g⁻¹ that is attributed to its developed microporosity as well as surface chemistry composed of basic groups facilitating electrostatic interactions with diclofenac anions. Desorption study showed that diclofenac is strongly bonded, albeit with a different degree depending on the modification of the CMK-carbon. The obtained results were compared with up-to-date literature regarding sorption of diclofenac by carbon-based sorbents.

Adsorption and desorption of heavy metals by the sewage sludge and biochar-amended soil

The goal of the study was to evaluate the application of biochar (BC) to the sewage sludge (SL) on the adsorption and desorption capacity of Cd(II), Cu(II), Ni(II) and Zn(II). The effect of biochar contribution in the sewage sludge (2.5, 5 and 10%) was investigated. The isotherms data were fitted to the Langmiur (LM), Freundlich (FM) and Temkin (TM) models. The best fitting for kinetic study was obtained for the pseudo-second-order equation. The best fitting of the experimental data was observed for the LM in the case of SL and BC, and for the FM in the case of SL- and SL/BC-amended soil. SL was characterized by even four-order higher sorption capacity than BC. The addition of the BC to the SL and next to the soil increased the adsorption capacity of the soil and the SL-amended soil. In the case of all investigated potentially toxic elements (PTEs), the highest adsorption capacity was achieved for SL-amended soil in comparison with the control soil. In the case of other experimental variants, the adsorption capacity of metal ions was as follows: 2.5% BC > 5.0% BC > 10% BC. The negative correlation between hydrated radius of metal ions and the kinetics of sorption was observed. However, the desorption of PTEs from BC/SL-amended soil was significantly lower than for SL-amended soil (except of Cd) and non-amended soil. It can be concluded that the addition of the biochar enhanced the immobilization of PTEs and reduced their bioavailability and mobility in the soil amended by the sewage sludge.

An ion-imprinted thiocyanato-functionalized mesoporous silica for preconcentration of gold(III) prior to its quantitation by slurry sampling graphite furnace AAS

A gold(III)-imprinted thiocyanato-functionalized silica network of type SBA-15 was prepared by co-condensation of tetraethoxysilane (TEOS) with thiocyanatopropyltriethoxysilane (TCTES) in the presence of Pluronic123 and Au(III) ions. Compared to the non-imprinted material, the imprint has a higher selectivity and adsorption capacity for Au(III). The maximum static adsorption capacity for Au(III) is 475 mg·g⁻¹ for the ion-imprinted, and 62 mg·g⁻¹ for the non-imprinted sorbent. The imprint was applied to the sorption of Au(III) from digested geological samples prior to its determination by graphite furnace atomic absorption spectrometry. Adsorption is fast and does not substantially prolong the analytical procedure. Under optimum conditions, the detection limit for Au(III) is 2 ng·g⁻¹. The method was validated by analyzing certified reference materials, and results were in good agreement with certified values. The procedure was successfully applied to the separation and determination of gold in complex geological samples.

Graphical abstract

Synthesis of biochar from residues after biogas production with respect to cadmium and nickel removal from wastewater

The objective of the study was to investigate the ability of biochars prepared under different temperatures (400 °C and 600 °C) from the residue of biogas production (RBP) for the adsorption of cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution. Furthermore, the RBP biochars adsorption capacity was compared with adsorption capacity of biochar produced from wheat straw at 600 °C (BCS600). The kinetics of the adsorption, the sorption isotherms, the influence of solution pH and the interfering ions (chlorides and nitrates) were investigated. The desorption of Cd(II) and Ni(II) by hydrochloric and nitric acid from biochars was also investigated. The different types of feedstock used for biochar (BC) preparation (RBP and biomass) determined the physico-chemical properties of biochars and hence their adsorption abilities. Generally, biochars produced from RBPs (regardless of temperature) had the greater capacity to adsorb Cd(II) and Ni(II) than the biochar produced from wheat straw. Of the tested models (Freundlich and Langmuir), the Langmuir model was demonstrated to be the best to describe the sorption of Cd(II) and Ni(II). For the kinetic study, the adsorption process proceeded the fastest for BCU400 than BCU600. Furthermore, BCU600 was the most resistant to the influence of interfering ions on adsorption. For the desorption study, BCU400 was characterized by the highest reproducibility of the surface. The comparison of the results obtained in each adsorption step between RBP biochars and BCS600 suggested that the residue from biogas production could be successfully applied for the removal of Cd(II) and Ni(II) ions from aqueous solutions.

Studies of cadmium(II), lead(II), nickel(II), cobalt(II) and chromium(VI) sorption on extracellular polymeric substances produced by Rhodococcus opacus and Rhodococcus rhodochrous

The adsorption of Cd(II), Pb(II), Ni(II), Co(II) and Cr(VI) ions on the extracellular polymeric substances (EPS) obtained from bacterial strain Rhodococcus opacus and Rhodococcus rhodochrous was investigated by the static sorption method. Influence of pH, time and temperature were studied. It was found that the influence of the pH value and time of adsorption depends on the type of adsorbed ions. For all investigated systems an increase of temperature above 35°C reduces adsorption. However, the static sorption capacities values oscillate around 1.5mmol/g, independently of the type of the studied metal ions. The adsorption mechanism of studied metal ions onto the tested EPSs seems to be very complex and it is probably due to an electrostatic attraction, a surface complex formation and chemical interaction between the metal ions and the functional groups (mainly hydroxyl, acetamido or amino groups) of bacterial extracellular biopolymers.

On the Adsorption of Chromium(VI) Ions on Dolomite and ‘Dolomitic Sorbents’

The sorption capability of raw and thermally treated dolomite samples with respect to toxic ions was estimated through the adsorption of chromium(VI) from aqueous solutions. The adsorption isotherms were shown to fit the well-known Freundlich equation. The results confirm the weak adsorption of chromium(VI) on raw dolomite relative to the other dolomite-derived sorbents. The influence of ionic strength on the adsorption was also determined.

Study of Chromium(VI) Adsorption from Aqueous Solution on to Activated Carbon

The adsorption of chromium(VI) from dilute aqueous solutions on to activated carbons at natural pH values was investigated. The activated carbons were modified to obtain materials with a well-defined surface containing inorganic impurities at ppb or ppm level. Measurements of the adsorption kinetics relative to the degree of granulation were undertaken. It was found that the reaction rate of the ions on the surface of the activated carbon rather than diffusion was the major process influencing the equilibrium. Surface reduction of CrVI to CrIII appeared to be the principal mechanism for the adsorption of chromium on the activated carbons studied. It was demonstrated experimentally that the presence of oxidizing agents dramatically changed the adsorption capacity of CrVI on the studied carbons. The influence of the ionic strength (controlled by the addition of NaCl) on the adsorption capacity was also studied. Variable and complex influences of the ionic strength on the adsorption capacity were observed.

Application of laboratory prepared and commercially available biochars to adsorption of cadmium, copper and zinc ions from water

The goal of the presented work was the evaluation and comparison of two biochars (produced from Sida hermaphrodita - BCSH/laboratory produced and from wheatstraw - BCS/commercial available) to adsorb heavy metal ions (Cd(II), Cu(II) and Zn(II)) from water. Kinetics of the sorption as well as sorption isotherms, the influence of solution pH and interfering ions were investigated. Different physico-chemical properties of biochars had the great influence on adsorption capacity. The greater adsorption efficiency was observed for BCSH than for BCS in the case of all investigated metals. The adsorption efficiency of BCSH was correlated with higher content of carbon and oxygen, what is equal with higher content of polar-groups on the BCSH surface e.g., -COOH. Furthermore, the molar ratio of O/C as well as polarity index (which was higher for BCSH) was also important parameters.

Sorption and desorption of Cr(VI) ions from water by biochars in different environmental conditions

In the present research, the potential of two biochars produced by the thermal decomposition of wheat straw (BCS) and wicker (BCW) for Cr(VI) ions removing from wastewater was investigated. The pH and the presence of chlorides and nitrates were also investigated. The Freundlich and Langmuir models were applied for the characterization of adsorption isotherms. The Langmuir model has better fitting of adsorption isotherms than the Freundlich model. The sorption process can be described by the pseudo second-order equation. The optimal adsorption capacities were obtained at pH 2 and were 24.6 and 23.6 mg/g for BCS and BCW, respectively. X-ray photoelectron spectroscopy (XPS) studies confirmed that Cr(III) ions were the most abundant chromium species on the biochars' surface. The results indicated that the sorption mechanism of Cr(VI) on biochar involves anionic and cationic adsorption combined with Cr(VI) species reduction.

Determination of bismuth in environmental samples by slurry sampling graphite furnace atomic absorption spectrometry using combined chemical modifiers

Slurry sampling graphite furnace atomic absorption spectrometry technique was applied for the determination of Bi in environmental samples. The study focused on the effect of Zr, Ti, Nb and W carbides, as permanent modifiers, on the Bi signal. Because of its highest thermal and chemical stability and ability to substantially increase Bi signal, NbC was chosen as the most effective modifier. The temperature programme applied for Bi determination was optimized based on the pyrolysis and atomization curves obtained for slurries prepared from certified reference materials (CRMs) of the soil and sediments. To overcome interferences caused by sulfur compounds, Ba(NO₃)₂ was used as a chemical modifier. Calibration was performed using the aqueous standard solutions. The analysis of the CRMs confirmed the reliability of the proposed analytical method. The characteristic mass for Bi was determined to be 16 pg with the detection limit of 50 ng/g for the optimized procedure at the 5% (w/v) slurry concentration.

Chemometric methods for studying the relationships between trace elements in laryngeal cancer and healthy tissues

A quick and reliable method for the evaluation and classification of two types of tissues is presented. Several chemometric methods were applied to evaluate multivariate data of the tissue samples with respect to the content of trace elements. The content of Pb, Al, Zn, Cd, Cu, Ni and Co was determined in samples of healthy and cancerous tissue obtained from 26 patients. Determination was done at milligram/kilogram level with inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectroscopy (AAS) techniques. Contents of trace metals in studied tissues are not normally distributed; however, normal distribution was confirmed for log values. There is a statistically significant difference in the content of Zn, Cd, Cu and Al (p<0.01) and Ni and Co (p<0.05) when healthy tissue is compared to cancerous one. Correlation between contents of trace elements for studied tissues was positive; the highest was found between Zn and Cu. A chemometric methodology seems to be a promising tool for classifications of the tissue samples.

Preparation and evaluation of Fe-loaded activated carbon for enrichment of selenium for analytical and environmental purposes

The adsorbent, based on the thermal modification of activated carbon impregnated by iron(III) nitrate(V), has been prepared and applied for selenium enrichment from aqueous solution. Various ratios of the impregnating agent to carbon mass were carefully examined with respect to selenium adsorption capacity and selectivity. The basic Se(VI) ions adsorption parameters affecting the adsorption ability onto the prepared activated carbons were studied. The carbon impregnated by 10% Fe(NO(3))(2) and thermally treated at 200 °C possessed the highest adsorption capacity and selectivity towards selenium ions. The physico-chemical characterization of the prepared adsorbents before and after selenium uptake were carried out using scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDX) and X-ray photoelectron spectroscopy (XPS). The studies confirmed the surface complexation reactions of iron species and selenium on the Fe-loaded activated carbon. Due to its high adsorption capacity enrichment of selenium on the studied adsorbent has been successfully applied for its determination in the complementary feeds, using the carbon slurry sampling graphite furnace atomic absorption spectrometry technique (GFAAS) and standard calibration method.

The content of cadmium, cobalt and nickel in laryngeal carcinoma

INTRODUCTION

The aim of the study was to determine the content of cadmium (Cd), cobalt (Co) and nickel (Ni) in the samples from laryngeal carcinoma in comparison with the level of these elements in the samples of healthy mucous membrane from the same larynx.

MATERIAL AND METHODS

The study was conducted on 43 patients with laryngeal carcinoma. The levels of Cd, Co, and Ni in carcinoma and healthy control tissues was determined by inductively coupled plasma optical emission spectrometry (ICP - OES) using sequential spectrometer.

RESULTS

No significant differences were found between the levels of the Cd, Co, and Ni in laryngeal carcinoma vs tissues without carcinoma. However, it was noted that the concentration of Cd in tumors of patients with metastases to cervical lymph nodes was significantly higher than in tumors without metastases. The content of Co was significantly higher in more advanced laryngeal tumors: in stage-T4 than in stage T3. It is of interest that the levels of Cd, Co and Ni were significantly higher in tumors in patients from rural than urban areas.

CONCLUSIONS

The imbalance in the level of nickel, cadmium and cobalt in laryngeal cancer may be due to a changed cellular metabolism in the cancer process. However, the results of our study reveal the significant differences in the concentration of these metals between patients from urban and rural areas which suggests that this fact may be related to environmental or occupational factors and therefore it requires further study.

Slurry sampling for the determination of thallium in soils and sediments by graphite furnace atomic absorption spectrometry

The analytical conditions for thallium determination in soils and sediments by slurry sampling graphite furnace atomic absorption spectrometry were studied and optimized. Elimination of a strong background for soils rich in organic materials by application of tungsten carbides coated graphite tubes/platforms was studied in detail. Tungsten carbides increased the maximum permissible pyrolysis temperature from 300 to 900 degrees C. The mechanism of tungsten carbide formation on different graphite surfaces was proposed. Application of a strong basic anion-exchange resin for interference elimination in thallium determination in marine sediments was described. Calibration was performed directly using aqueous standards both for soil and sediment analysis. Analysis of CRM confirmed the reliability of the approach. The precision and accuracy of thallium determination by the described method for soils and sediments was acceptable. A characteristic mass of 13.8 pg was obtained and the limit of detection for the proposed method was around 0.06 microg g(-1) Tl.

Determination of selenium in soils by slurry-sampling graphite-furnace atomic-absorption spectrometry with polytetrafluoroethylene as silica modifier

A 6% slurry of polytetrafluoroethylene (PTFE) in 4% hydrofluoric acid and 1% nickel nitrate were used as modifiers for determination of selenium in soils by GF AAS. PTFE was used to remove silica from the soil sample, because this resulted in severe matrix effects. The temperature of fluorination, determined thermogravimetrically, was 600 degrees C. The yield of fluorination depends on the molar ratio of PTFE/silica, particle size, and the time and temperature of fluorination. The soil samples were pretreated with a small amount of concentrated hydrofluoric acid placed directly in the cup of autosampler. The results for the determination of selenium in the reference soil materials by means of the slurry-sampling technique and use of aqueous standards are in good agreement with the certified values.