Zinc Adsorption Capacity Research Articles

Metal and proton adsorption capacities of natural and cloned Sphagnum mosses

Terrestrial mosses are commonly used as bioindicators of atmospheric pollution. However, there is a lack of standardization of the biomonitoring preparation technique and the efficiency of metal adsorption by various moss species is poorly known. This is especially true for in vitro-cultivated moss clones, which are promising candidates for a standardized moss-bag technique. We studied the adsorption of copper and zinc on naturally grown Sphagnum peat moss in comparison with in vitro-cultivated Sphagnum palustre samples in order to provide their physico-chemical characterization and to test the possibility of using cloned peat mosses as bioindicators within the protocol of moss-bag technique. We demonstrate that in vitro-grown clones of S. palustre exhibit acid–base properties similar to those of naturally grown Sphagnum samples, whereas the zinc adsorption capacity of the clones is approx. twice higher than that of the samples from the field. At the same time, the field samples adsorbed 30–50% higher amount of Cu2+ compared to that of the clones. This contrast may be related to fine differences in the bulk chemical composition, specific surface area, morphological features, type and abundance of binding sites at the cell surfaces and in the aqueous solution of natural and cloned Sphagnum. The clones exhibited much lower concentration of most metal pollutants in their tissues relative to the natural samples thus making the former better indicators of low metal loading. Overall, in vitro-produced clones of S. palustre can be considered as an adequate, environmentally benign substitution for protected natural Sphagnum sp. samples to be used in moss-bags for atmospheric monitoring.

Zinc sorption onto different particle sizes of compost from aqueous solution

The zinc adsorption capacity and kinetics of different compost particle sizes were investigated using batch and column experiments. The results indicated that the particle size influenced the sorption process. The surface area per unit weight of the sorbent increased as the particle size decreased. The adsorption equilibrium data fitted very well both the Langmuir and Freundlich isotherms. The estimated sorption capacities of different compost particle size in the column experiment were 22.9 mg/g (0.60 mm), 17.3 mg/g (1.18 mm) and 12.7 mg/g (4.75 mm) compared with Langumir isotherm predictions of 26.6 mg/g (0.60 mm), 18.7 mg/g (1.18 mm) and 15.6 mg/g (4.75 mm). It is evident that compost has a high affinity for zinc which reflects the physicochemical properties of the compost particles. These properties indicate that weak physical sorption and strong chemical sorption is likely to occur between zinc and the compost particles.

Adsorption of Zn2+ on Algerian untreated bentonite clay

This work has the purpose of evaluating the removal of zinc from aqueous solutions using Algerian untreated bentonite clay as an adsorbent. The choice of using natural untreated clay is justified by the fact that it is both a low cost and friendly environmental adsorbent material. This local bentonite is a montmorillonite clay type with a relatively high cationic exchange capacity of 136.2 meq/100 g. Calcium is the main exchangeable cation. A granulometric analysis shows that 49.1% of the clay particles are submicronic. The zinc adsorption capacity of bentonite was studied in batch mode. A kinetic study shows a fast removal capacity and a highly influenced bentonite adsorption capacity by the operational parameters such as contact time, mass of adsorbent, metal concentration, pH, and temperature. Fifty percent of the Zinc was removed during the first 5 min and equilibrium is reached in 1 h. A maximal removal capacity is obtained for a bentonite concentration of 5 g L−1 and a zinc initial concentration of 100 mg L−1. A pseudo-second-order kinetic model could be fitted to the experimental data. The equilibrium data could be fitted with a Langmuir isotherm equation. Depending on the negative value of ΔG, the adsorption of Zn2+ on SIG untreated bentonite surfaces was spontaneous and the adsorption was an endothermic process.

Examination of zinc adsorption capacity of soils treated with different pyrolysis products

Abstract Organic matter input into soils is essential regarding agricultural, environmental and soil science aspects as well. However, the application of the pyrolysed forms of biochars and materials with different organic matter content gained more attention in order to decrease the emission of the green house gases (CO2, N2O) from the soil. During pyrolysis, the materials containing high organic matter (biomass-originated organic matter) are heated in oxygen-free (or limited amount of oxygen) environment. As a result, the solid phase, which remains after eliminating the gases and liquid phase, is more stable compared to the original product, it cannot be mineralized easily in the soil and its utilization is more beneficial in terms of climatic aspects. Furthermore, it can improve soil structure and it can retain soil moisture and cations in the topsoil for long periods of time, which is very important for plants. In our experiment, the effects of biochar and bone char were examined on soils by zinc adsorption experiments. Based on our experiments, we concluded that the pyrolysis products can have significant Zn adsorption capacity compared to the soil. Bone ash can adsorb more Zn than the charcoal product. The Zn adsorption capacity of soils treated by pyrolysis products can be described by Langmuir adsorption isotherms. However, based on the amount of pyrolysis products, one or two term Langmuir isotherm fits well on the experiment data, which depends on the time the pyrolysis product has spent in the soil.

Adsorption behavior of Zn(II) ions on synthetic hydroxyapatite

The adsorption of Zn2+ on synthetic hydroxyapatite was investigated using a batch method and a radiotracer technique. The commercial hydroxyapatite and hydroxyapatite of high crystallinity with Ca/P ratio of 1.563:1.688 prepared by a wet precipitation process were used in this study. The adsorption of zinc on hydroxyapatite was pH independent ranging from 4.5 to 6.5 as a result of buffering properties of hydroxyapatite. The adsorption of zinc was rapid and the percentage of Zn adsorption on both samples of hydroxyapatite was >96% during the first 30 min of the contact time. The experimental data for adsorption of zinc have been interpreted in terms of Langmuir isotherm and the values of maximum adsorption capacity of zinc on a commercial hydroxyapatite and hydroxyapatite prepared by wet precipitation process were calculated to be 0.437 and 0.605 mmol g−1, respectively. The competition effect of Fe2+ towards Zn2+ adsorption was stronger than that of Ca2+, Mg2+, and Sr2+ ions. The ability of the bivalent cations to depress the adsorption of zinc on hydroxyapatite was in the following order: Fe2+ > Ca2+ > Sr2+ ≈ Mg2+.

Zinc adsorption in bentonite clay: influence of pH and initial concentration

This paper evaluated the adsorption capacity of zinc by Bofe bentonite clay. Bofe clay was subjected to a thermal treatment for optimizing its adsorption capacity. The kinetic equilibrium of the process was studied in a finite bath system and experiments were performed by varying pH, the amount of adsorbent and initial concentration of the metal. The Langmuir and Freundlich models were used for the analysis of adsorption equilibrium. The physicochemical characterization of clay, before and after the adsorption process, included the techniques of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and N 2 physisorption. The calcined Bofe clay is able to remove zinc from synthetic wastewater. Langmuir model provided the best fit for sorption isotherms with a maximum amount of metal adsorbed of 4.95 mg of metal g -1 of calcined clay. The adsorption was strongly influenced by the initial conditions and modifies the physicochemical characteristics of the clay.

A Comparison Between a Low-Cost Sorbent and an Activated Carbon for the Adsorption of Heavy Metals from Water

In this work, a coal combustion ash (CCA) has been tested as an alternative low-cost sorbent to commercial activated carbons (GAC) for cadmium and zinc removal from polluted water. To this aim, the effect of pH and metal concentration on CCA adsorption capacity has been investigated, and a comparative analysis with GAC has been carried out in the same experimental conditions. Furthermore, in order to improve CCA adsorption capacity, two different activation treatments of raw CCA have been tested. In particular, the CCA was subjected to a gasification process conducted with steam and to different acidic treatments, conducted either with hydrochloric acid or nitric acid at different acid concentrations. Experimental results showed that all the acid treatments determined a substantial reduction of both cadmium and zinc adsorption capacity. Differently, the steam gasification determined a substantial increase in adsorption capacity with respect to raw CCA, in particular for zinc as its adsorption capacity resulted even higher than the correspondent of GAC. Finally, a thorough analysis of sorbent physical and chemical properties and of adsorption data allowed the individuation of the main cadmium/zinc adsorption mechanism both on CCA and activated carbon, adequately described by the Freundlich model.

Biosorption of zinc from aqueous solution using chemically treated rice husk.

In this study, adsorption of zinc onto the adsorbent (untreated rice husk and NaOH-treated rice husk) was examined. During the removal process, batch technique was used, and the effects of pH and contact time were investigated. Langmuir isotherm was applied in order to determine the efficiency of NaOH-treated rice husk used as an adsorbent. The zinc adsorption was fast, and equilibrium was attained within 30 min. The maximum removal ratios of zinc for untreated rice husk and NaOH-treated rice husk after 1.5 h were 52.3% and 95.2%, respectively, with initial zinc concentration of 25 mg/L and optimum pH of 4.0. Data obtained from batch adsorption experiments fitted well with the Langmuir isotherm model. Maximum adsorption capacity of zinc onto untreated rice husk and NaOH-treated rice husk was 12.41 mg/g, and 20.08 mg/g respectively, at adsorbent dosage of 1 g/L at 25°C. The nature of functional groups (i.e., amino, carboxyl, and hydroxyl) and metal ion interactions was examined by the FT-IR technique. It was concluded that the NaOH-treated rice husk had stronger adsorption capacity for Zn2+ compared with the untreated rice husk. The NaOH-treated rice husk is an inexpensive and environmentally friendly adsorbent for Zn2+ removal from aqueous solutions.

Zn(II) Removal with Activated Firmiana Simplex Leaf: Kinetics and Equilibrium Studies

As is known, zinc pollution has been a public environmental issue for a long time. Accordingly, the major objective of this study is to examine the effect of activated Firmiana simplex leaf on Zn(II) removal from aqueous solution. The result shows that activated Firmiana simplex leaf can remove Zn(II) effectively at 250°C due to the preservation of amine, carboxyl, and phosphate groups. Several factors were determined to have significant effects on the adsorption of Zn(II), including the adsorbent component, dosage, initial concentration, solution pH, temperature, and duration. Pseudo first order and pseudo second order kinetics equations were used to predict the kinetic and thermodynamic constants that reveal the endothermic and spontaneous nature of the adsorption. Using the Langmuir model, the maximum zinc adsorption capacity was calculated to be 55.096 mg/ g, which was subsequently confirmed by Fourier transformed infrared radiation (FT-IR) analyses and X-ray diffraction (XRD) spectra.

Accumulation and mobility of zinc in soil amended with different levels of pig-manure compost

Applying manure compost not only results in zinc accumulation in the soil but also causes an increase in zinc mobility and enhances zinc leaching. In this study, the physical and chemical characteristics of zinc, zinc profiles, and zinc balance were investigated to characterise the fate of zinc in fields where the quality and amount of pig manure compost applied have been known for 13 years. Moreover, we determined zinc fractionation in both 0.1 mol L−1HCl-soluble (mobile) and -insoluble (immobile) fractions. Adsorption of zinc in the soil was enhanced with increasing total carbon content following the application of pig manure compost. The 159.6 mg ha−1 year−1manure applied plot (triplicate) exceeded the Japanese regulatory level after only 6 years of applying pig manure compost, whereas the 53.2 mg ha−1 year−1 manure applied plot (standard) reached the regulatory level after 13 years. The zinc loads in the plots were 17.0 and 5.6 kg ha−1 year−1, respectively. However, 5.9 % and 17.2 % of the zinc loaded in the standard and the triplicate pig manure compost applied plots, respectively, were estimated to be lost from the plough layer. Based on the vertical distribution of mobile and immobile zinc content, a higher rate of applied manure compost caused an increase in the mobile zinc fraction to a depth of 40 cm. Although the adsorption capacity of zinc was enhanced following the application of pig manure compost, a greater amount of mobile zinc could move downward through the manure amended soil than through non manure-amended soil.

Production of Biosorbents from Waste Olive Cake and Its Adsorption Characteristics for Zn2+ Ion

In this study, waste olive cake (OC) was utilized as the raw material for the production of biosorbents by chemical treatment and its adsorption capacity for zinc ion was evaluated. Tests were conducted with the total biomass (T) and with the fraction > 2.00 mm (P), in order to determinate the influence of this fractionation step on subsequent treatments. Two chemical agents were used: sulfuric acid and sodium hydroxide. The parameters studied include physical and chemical properties of materials, contact time, pH, adsorbent dose and initial concentrations. The kinetic data were best fitted to the pseudo-second order model. Zinc binding is strongly pH dependent, with more zinc ions bound at a higher pH (5-7 in a range of 3-7). Both Langmuir and Freundlich models are well suited to fit the data on sorption of zinc by OC. Data on sorption of zinc by waste olive cake treated with sulfuric acid (OC-H) was better described by the Freundlich model. Zinc sorption by waste olive cake treated with sodium hydroxide (OC-OH) was better described by the Langmuir model. Results show OC-OH is a biosorbent with a superior adsorption capacity for zinc than OC-H. The maximum adsorption capacity obtained from the Langmuir isotherms increases in the order (mg/g): OC-HT (14), OCT (22) and OC-OHT (27). Results also indicate that the previous fractionation step doesn´t produce a biosorbent with a superior adsorption capacity.

Equilibrium and thermodynamic analysis of zinc ions adsorption by olive oil mill solid residues

This work investigated the equilibrium batch dynamics of using olive oil mill solid residues as an adsorbent for zinc removal from aqueous solutions. It was found that a sorbent concentration of 4 g L −1 achieved the best removal percentage and the best sorbent capacity. Adsorption equilibrium was reached in 60 min for an initial zinc concentration of 0.25 mmol/L and 180 min for an initial zinc concentration of 1–3 mmol/L. A particle size of olive mill residue ranging from 0.85 to 1.18 mm was used in the study. It was found that the maximum adsorption capacity of zinc was at a pH value of 5.0. It was found that q max for zinc ions, was 5.63, 6.46, and 7.11 mg g −1 at temperature values of 298, 308, and 328 K, respectively. The data pertaining to the sorption dependence upon metal ion concentration could be fitted to a Langmuir isotherm model. The second-order kinetic model provided the best correlation of the data. The change in entropy (Δ S°) and heat of adsorption (Δ H°) for zinc ions adsorption on olive mill solid residues were estimated as −1419 kJ kg −1 K −1 and 4.7 kJ kg −1, respectively. The examined low-cost adsorbent could offer an effective way to decrease zinc ions concentration in wastewater.

Heavy metals retention capacity of a non-conventional sorbent developed from a mixture of industrial and agricultural wastes

Zinc and copper removal from aqueous solutions using brine sediments (industrial residue), sawdust (agricultural residue) and the mixture of both materials has been researched through batch and column tests. Brine sediments were found to be mainly constituted by halite and calcite, while its main cations exchangeable were sodium, calcium, magnesium and potassium. In sawdust the main exchangeable cations detected were calcium, magnesium, sodium and potassium. FT-IR spectra of sawdust and brine sediment–sawdust mixture showed that brine sediments produced important changes in carboxylic, alcoholic and phenolic groups present in the sawdust. The maximum zinc adsorption capacity was found to be 4.85, 2.58 and 5.59 mg/g using an adsorbent/solution ratio of 1/40, for brine sediments, sawdust and the mixture, respectively. For copper, the maximum adsorption capacity was found to be 4.69, 2.31 and 4.33 mg/g, using adsorbent/solution ratios of 1/40, for brine sediments, sawdust and the mixture, respectively. Maximum copper adsorption capacity of the mixture, on the contrary to zinc adsorption, was lightly inferior to maximum adsorption capacity obtained in brine sediments. Adsorption isotherms data adjusted better to the Langmuir model. Additionally, columns reached the saturation point at 690 min for zinc and 360 min for copper. The main mechanism involved in the removal of both metals may be the ionic exchange between sodium and calcium ions present in brine sediments and H + present in functional groups of sawdust. The use of brine sediments, sawdust and their mixture, presents an interesting option both, for wastewater decontamination (as a possible non-conventional sorbent for the removal of heavy metals) and as a waste recycling option.

Zinc Isotope Fractionation on Benzo-15-crown-5 Resin by Liquid Chromatography

Chromatographic fractionation of zinc isotopes was performed on the synthesized benzo-15-crown-5 resin as a column packing material at 323K in the breakthrough manner for both a frontal and a rear bands. Zinc adsorption capacity was affected by anion chloride concentration and solvent dielectric constant. The heavier zinc isotopes were found enriched to the solution phase and the lighter zinc isotope was concentrated on the resin phase. The frontal maximum enrichment ratio for isotopic pair of 68Zn/64Zn was 1.0081. The isotope separation coefficients for isotopic pair of 68Zn/64Zn for frontal and rear band, were 5.3 × 10−4, 4.5 × 10−4, respectively.

Zinc Isotope Fractionation on Benzo-15-crown-5 Resin by Liquid Chromatography

Chromatographic fractionation of zinc isotopes was performed on the synthesized benzo-15-crown-5 resin as a column packing material at 323K in the breakthrough manner for both a frontal and a rear bands. Zinc adsorption capacity was affected by anion chloride concentration and solvent dielectric constant. The heavier zinc isotopes were found enriched to the solution phase and the lighter zinc isotope was concentrated on the resin phase. The frontal maximum enrichment ratio for isotopic pair of 68Zn/64Zn was 1.0081. The isotope separation coefficients for isotopic pair of 68Zn/64Zn for frontal and rear band, were 5.3 × 10−4, 4.5 × 10−4, respectively.

Heavy metal adsorption by different minerals: application to the remediation of polluted soils

We studied the heavy-metal adsorption capacity of various minerals in order to evaluate their potential for the reduction of metal mobility and bioavailability and their possible application for the remediation of polluted soils in the Guadiamar valley. The study (batch tests) of zinc adsorption capacity of clays (sepiolites, palygorskites, and bentonite from different mineral deposits) and a soil unaffected by the toxic spill at the P3 site (Puente las Doblas) showed a relative low adsorption capacity for Zn 2+. In the case of the sepiolite from Orera deposit, the maximum retention capacity was obtained for Cd 2+ (8.3 mg g −1), followed by Cu 2+ (6.9 mg g −1), and finally Zn 2+ (5.7 mg g −1). We conclude that the capacity of adsorption of the clays and soil P3 is insufficient to immobilise heavy metals because of the high pollution levels of the soils in the Guadiamar valley. Only goethite (from Cerro del Hierro and Sierra de la Culebra) has sufficient adsorption capacity (between 3 and 4 mg g −1) to immobilise As in the highly polluted soil. Zeolite (NaP1), synthesised from Los Barrios fly ash, showed high retention efficiency for monovalent and divalent cations. Thus, the leaching and ionic exchange tests performed with mixtures of soil with pyrite slurry and NaP1 zeolites showed a high reduction on the mobility of Tl, Zn, Cd, Mn and Co (between 63 and 100%). The retention efficiency (for some of the metals considered) depended, not only on the ionic exchange capacity of the NaP1 zeolite, but also on the decrease of the acidity induced by the zeolitic product.

Adsorption of zinc onto peat from peatlands of Poland and Israel

Peat, defined as young Quaternary, mainly Holocene, organogenic sedimentary rock in the first stage of coalification, has received increasing attention due to its potential to act as an ubiquitous effective agent for the recovery of valuable metals, for the removal of metal ions from dumping site leachate and wastewater, or for retrospective monitoring of their migration and accumulation in the environment. For these purposes, adsorption capacity and binding strength of peat with respect to the metal ions under different conditions, as well as the mechanism of binding–release should be thoroughly known. To date, this knowledge is still limited. In this paper, results of studies on adsorption–desorption properties of Zn 2+, which is one of the most mobile trace metals in the environment, in representative Polish and Israeli peat samples are presented. Batch studies were performed for Zn 2+ in both single cation and a binary system (Zn–Cd) at pH 4.0. Column experiments under saturated flow conditions with Zn concentrations of 250 and 500 mg dm −3 in the input solution at pH 4.0 (monometallic system) were also conducted. Finally, batch and column zinc adsorption experiments on selected peat samples were carried out using real multi-component wastes from the electroplating process. To assess the binding strength of peat with respect to zinc, sequential extraction by Tessier et al. (1979)modified by Kersten and Förstner (1988) was applied. The adsorption capacity for zinc of low-moor Polish peat, which is typical for the Northern Hemisphere with pH 5.02–6.54, was 15,800 to 33,700 mg Zn kg −1. Lower values were found for the Israeli peat. The presence of mass equivalent amounts of Cd showed only a moderate suppressing influence on the uptake of Zn by different peat matter. This suggests a weak competition of metal ions for adsorption sites available, despite binding of these metals in similar mass ratios in the same most labile fractions. There was, however, a difference in the binding of Zn and Cd in the more stable fractions, where no competition between Zn and Cd occurred. A significant difference in fractionation of Zn sorbed in batch vs. column experiments, was indicated. In particular, higher Zn enrichment in the `insoluble organic' fraction under dynamic flow conditions was observed. Desorption experiments proved that zinc can be partially released with acid treatment from the labile fractions.