Determination and modelling of effects of pH on peat biosorption of chromium, copper and cadmium

Unlocking Cd(II) biosorption potential of Candida tropicalis XTA 1874 for sustainable wastewater treatment

Cd(II) is a potentially toxic heavy metal having carcinogenic activity. It is becoming widespread in the soil and groundwater by various natural and anthropological activities. This is inviting its immediate removal. The present study is aimed at developing a Cd(II) resistant strain isolated from contaminated water body and testing its potency in biological remediation of Cd(II) from aqueous environment. The developed resistant strain was characterized by SEM, FESEM, TEM, EDAX, FT-IR, Raman Spectral, XRD and XPS analysis. The results depict considerable morphological changes had taken place on the cell surface and interaction of Cd(II) with the surface exposed functional groups along with intracellular accumulation. Molecular contribution of critical cell wall component has been evaluated. The developed resistant strain had undergone Cd(II) biosorption study by employing adsorption isotherms and kinetic modeling. Langmuir model best fitted the Cd(II) biosorption data compared to the Freundlich one. Cd(II) biosorption by the strain followed a pseudo second order kinetics. The physical parameters affecting biosorption were also optimized by employing response surface methodology using central composite design. The results depict remarkable removal capacity 75.682 ± 0.002% of Cd(II) by the developed resistant strain from contaminated aqueous medium using 500 ppm of Cd(II). Quantitatively, biosorption for Cd(II) by the newly developed resistant strain has been increased significantly (p < 0.0001) from 4.36 ppm (non-resistant strain) to 378.41 ppm (resistant strain). It has also shown quite effective desorption capacity 87.527 ± 0.023% at the first desorption cycle and can be reused effectively as a successful Cd(II) desorbent up to five cycles. The results suggest that the strain has considerable withstanding capacity of Cd(II) stress and can be employed effectively in the Cd(II) bioremediation from wastewater.

The effects of earthworm inoculation on cadmium-contaminated rice field in Southern China: a pot experiment and a field test

Currently, the effects of earthworm inoculation on cadmium-contaminated rice field remain unclear. In this study, four treatments were tested, including rice monoculture (CK), earthworm inoculation with low density (L, 30 g/m2), middle density (M, 60 g/m2), and high density (H, 90 g/m2). The pot and field experiment were conducted in Hunan Province, China. In the pot experiment, the H treatment significantly decreased the available cadmium concentration in 0 ~ 20 cm soil by 5.21% ~ 16.51%, and the M treatment significantly decreased in 0 ~ 10 cm soil by 7.29% ~ 8.96%. The H treatment significantly decreased the total cadmium concentration in 0 ~ 5 cm soil by 10.36%. Moreover, the earthworm inoculation treatments significantly reduced cadmium accumulation in rice organs. In the field experiment, the M and H treatment decreased the available cadmium concentration in 0 ~ 20 cm soil by 14.05% ~ 47.52% and the H treatment decreased the total cadmium concentration in 0 ~ 20 cm soil by 0.78% ~ 5.75% although there was no significant difference. Furthermore, the earthworm inoculation treatments significantly decreased cadmium accumulation in part of rice organs. In conclusion, this study recommends that earthworm inoculation is an effective method of controlling cadmium contamination for rice production.

Evidences for the augmented Cd(II) biosorption by Cd(II) resistant strain Candida tropicalis XTA1874 from contaminated aqueous medium

Cadmium is one of the most dreadful heavy metals and is becoming a major toxicant in ground water with increasing concentration above the WHO Guidelines in drinking water (0.003 mg/L). The potential sources of cadmium include sewage sludge, phosphate fertilizers and ingredients like Ni-Cd batteries, pigments, plating and plastics. Cadmium levels are increased in water owing to the use and disposal of cadmium containing ingredients. Water draining from a landfill may contain higher cadmium levels. The authors have tried to evaluate the optimized nutritional conditions for the optimal growth and Cd(II) remediation capacity for a developed Cd(II) resistant yeast strain named Candida tropicalis XTA 1874 isolated from contaminated water-body in West Bengal. By analyzing the optimization conditions, a synthetic medium was developed and the composition has been given in the main text. The strain showed much better Cd(II) adsorption capacity under the optimized nutritional conditions (Mean removal = 88.077 ± 0.097%).

Phytoremediation of nickel and chromium-containing industrial wastewaters by water lettuce (Pistia stratiotes)

This study was conducted to assess the phytoremediation potential of Pistia stratiotes for post-treatment of Ni(II) and Cr(III)-containing industrial wastewater effluents in mono (synthetic wastewater) and bimetallic systems (real wastewater). Differences were seen in metal uptake, growth performance, and metal accumulation of the plants. In the monometallic system, the highest removal efficiency was calculated as 77.50% for Cr(III) and 70.79% for Ni(II) at 5 mg L^-1 concentration. At 1.25 mg L^-1 concentration, the bioconcentration factor of P. stratiotes was calculated as 734.2 for Ni(II) and 799.0 for Cr(III). To assess the effects of metal stress on plants, photosynthetic pigments and percent growth rates were also investigated. The percent growth rate increased from 38.22 to 81.74% for Ni and decreased from 87.53 to 43.18% for Cr(III) when the metal concentrations increased from 1.25 to 5 mg L^-1. Toxicity symptoms were less severe in plants exposed to low Ni concentrations. The greatest reduction in chlorophyll was observed at 5 mg L^-1 Ni concentration. P. stratiotes showed better performance in the monometallic system. It was concluded based on present findings that P. stratiotes could potentially be used for the post-treatment of wastewaters containing Ni and Cr.Novelty Statement Previous phytoremediation studies were mostly conducted only in either mono- or multi-metallic systems. In this study, mono- and bimetallic systems were assessed together and the feasibility of research findings on a large scale was investigated in detail. Present findings may also aid in the development of phyto-remedial strategies and the identification of Ni and Cr toxicity in macrophytes. Pistia stratiotes are already known for its incredible potential in removing metals and other contaminants from wastewater effluents. However, most studies only present data regarding the plant performance in laboratory studies (synthetic wastewater), while this study provides some important additional information on natural effluent conditions, which transform the presented data more interesting from a practical point of view.

Modification of Natural Peat for Removal of Copper Ions from Aqueous Solutions

This study aimed at estimating peat adsorption properties for copper ion removal from aqueous solutions during peat modification. Two peat modifications have been studied using batch tests and quantitatively reproduced with instrumental analysis by using spectrometric, potentiometric, and thermodynamic modeling methods. The first variation—mechanical activation—was carried out in a planetary mill; for the second one—mechanochemical activation—dry sodium percarbonate (Na2CO3∙1.5H2O2) was added. The adsorption of copper ions was studied in the concentration range from 10–150 mg/L with an interaction time from 0.25–12 h. Both modifications led to significant changes in the interaction energy in the adsorption layer; thus, the acceptor properties of macromolecules were enhanced from natural peat to mechanically activated peat and mechanochemically activated peat. FTIR spectra, specific surface area characteristics, and sorption experiments show the predominantly chemical nature of copper sorption. Maximum adsorption capacity was determined to be 24.1, 42.1, and 16.0 mg/g for natural peat, mechanically activated peat, and mechanochemically activated peat, respectively. The example of peat mechanochemically oxidized with Na2CO3∙1.5H2O2 shows that the improvement in the physicochemical properties (CBET and specific surface area) plays a smaller role in the sorption capacity in relation to copper ions than the presence of phenolic and carboxyl groups, the content of which decreases during oxidation.

Influence of pH on heavy metal speciation and removal from wastewater using micellar-enhanced ultrafiltration

pH plays an important role in heavy metal removal during micellar-enhanced ultrafiltration (MEUF). In the present work, the influence of pH on heavy metal speciation and removal from wastewater by MEUF was investigated using an anionic surfactant (sodium dodecyl sulfate, SDS) and a hydrophilic membrane (polyether sulfone). Experiments were performed with pH values in the range of 1-12. Metal ion removal efficiency (R) was used to assess the effects of the MEUF process. Results showed that better removal rate of copper and cadmium was achieved at high pH values (pH > 3) with SDS feed concentration of 8 mM, while the optimal pH range was 3-10 for zinc and lead. The corresponding efficiencies for heavy metal removal decreased with the increasing feed concentration of metal ions under the pH conditions of 1-12. Furthermore, the heavy metal ion removal rate (50 mg/L) followed the order of Pb²⁺ > Cd²⁺ > Zn²⁺ > Cu²⁺. These results showed that pH is a key parameter in metal ion speciation and removal during MEUF.

Effectiveness of lime and peat applications on cadmium availability in a paddy soil under various moisture regimes

In paddy soils, amendments and moisture play important role in the immobilization of cadmium (Cd). The effects of applying lime, peat, and a combination of both on soil Eh, pH, and Cd availability in contaminated soils were investigated under wetted (80 ± 5 % of water holding capacity) and flooded (completely submerged) conditions. In wetted soils, there was little change in Eh, compared to flooded soils where Eh reduced rapidly. Amendments of lime only or in a mixture with peat increased soil pH to different degrees, depending on the lime application rate. However, peat addition only slightly affected soil pH. The decreased Cd availability in flooded soils was related to submergence duration and was significantly lower than that in wetted soils after 14 days. Liming wetted and flooded soils decreased exchangeable Cd and increased carbonates or Fe-Mn oxides bound fractions, while peat addition transformed Cd from carbonates to organic matter bound fractions. The combined application of peat and lime generally showed better inhibitory effects on the availability of Cd than separately application of lime or peat. Higher application rates of lime, peat, or their mixture were more effective at reducing Cd contamination in flooded soil. This indicates that application of peat and lime mixture under flooded conditions was most effective for in situ remediation of Cd-contaminated soils. Further studies are required to assess the long-term effectiveness of the peat and lime mixture on Cd availability in paddy soils.

The application of biosorption for production of micronutrient fertilizers based on waste biomass

In the present paper, new environmental-friendly fertilizer components were produced in biosorption process by the enrichment of the biomass with zinc, essential in plant cultivation. The obtained new preparations can be used as controlled release micronutrient fertilizers because microelements are bound to the functional groups present in the cell wall structures of the biomass. It is assumed that new fertilizing materials will be characterized by higher bioavailability, gradual release of micronutrients required by plants, and lower leaching to groundwater. The biological origin of the material used in plant fertilization results in the elimination of toxic effect towards plants and groundwater mainly caused by low biodegradability of fertilizers. Utilitarian properties of new formulations enable to reduce negative implications of fertilizers for environmental quality and influence ecological health. In this work, the utilitarian properties of materials such as peat, bark, seaweeds, seaweed post-extraction residues, and spent mushroom substrate enriched via biosorption with Zn(II) ions were examined in germination tests on Lepidium sativum. Obtained results were compared with conventional fertilizers—inorganic salt and chelate. It was shown that zinc fertilization led to biofortification of plant in these micronutrients. Moreover, the mass of plants fertilized with zinc was higher than in the control group.

Biosorption of Mercury (II) from Aqueous Solutions onto Fungal Biomass

The biosorption of mercury (II) on 14 fungal biomasses, Aspergillus flavus I-V, Aspergillus fumigatus I-II, Helminthosporium sp., Cladosporium sp., Mucor rouxii mutant, M. rouxii IM-80, Mucor sp 1 and 2, and Candida albicans, was studied in this work. It was found that the biomasses of the fungus M. rouxii IM-80, M. rouxii mutant, Mucor sp1, and Mucor sp 2 were very efficient removing the metal in solution, using dithizone, reaching the next percentage of removals: 95.3%, 88.7%, 80.4%, and 78.3%, respectively. The highest adsorption was obtained at pH 5.5, at 30°C after 24 hours of incubation, with 1 g/100 mL of fungal biomass.

Adsorption of Mixtures of Toxic Metal Ions Using Non-Viable Cells of Saccharomyces Cerevisiae

The use of waste biomaterial for the adsorption of heavy metal ions is an economically appealing alternative to conventional metal ion removal methods. In the present work, S. cerevisiae biomass has been shown to be capable of the simultaneous removal of more than 98% of Pb(II) ions, 60% of Zn(II) ions and up to 55% of Cu(II) ions from aqueous solutions in the 10–50 mg/ℓ concentration range. Model equations describing the removal efficiency of each metal ion were determined using Response Surface Methodology (RSM) with respect to operating conditions such as pH, initial metal ion concentration and biomass dosage. Characterization of the metal ion–biomass interactions responsible for biosorption was studied employing zeta potential measurements, BET, FT-IR and EDX techniques; these indicated that the uptake of metal ions by non-living yeast was a surface adsorption phenomenon. The results proved the involvement of an ion-exchange mechanism between the adsorbing metal ions and the cell walls. In the presence of the complete range of metal ions studied, yeast cells were more selective towards Pb(II) ions.

Biosorption of Cr(III) using in natura and chemically treated tropical peats

The physicochemical characteristics of three Brazilian peats were investigated using elemental analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD) and studies of Cr(III) biosorption based on adsorption isotherms. Adsorption of Cr(III) by in natura peat from Santo Amaro das Brotas (Sergipe State) was much greater than by peats from either Ribeirão Preto (São Paulo State) or Itabaiana (Sergipe State), with adsorption capacities (q) of 4.90+/-0.01, 1.70+/-0.01 and 1.40+/-0.01 mg g(-1), respectively. Pre-treatments with HCl and NaOH+HCl reduced adsorption by the Santo Amaro das Brotas peat, showing that adsorption efficiency was associated with the amount of organic matter present. Conversely, increase in the mineral content following pre-treatment increased adsorption of Cr(III) by the Ribeirão Preto and Itabaiana peats. Highest adsorption (retention >95.0%) was achieved at equilibrium pH 4.0 using the Santo Amaro das Brotas peat. Experimental data for the adsorption of Cr(III) from aqueous solution onto this peat were fitted to the Langmuir equation, from which an equilibrium adsorption capacity, q(max), of 5.60 mg g(-1) was obtained, which was close to the experimentally determined value.

Studies on chromium(III) removal from aqueous solutions by sorption on Sphagnum moss peat

Batch sorption experiments were performed for the removal of chromium(III) ions from aqueous solutions using Romanian Sphagnum moss peat (untreated and treated with NaCl solution) as sorbent. In order to establish the best conditions for the sorption of chromium(III), the influence of initial pH, contact time, peat dose and metal ion concentration was investigated. The Freundlich, Langmuir and Dubinin-Radushkevich models were applied to describe the sorption isotherms and to calculate its constants. The experimental data fitted well to the Langmuir model with a maximum sorption capacity of 18.6 mg Cr(III)/g of peat. The mean free energy of sorption suggests that the binding of Cr(III) on peat occurred through an ion exchange mechanism. The kinetic data evaluated by pseudo-first order and pseudo-second order kinetic models showed that the sorption of chromium onto the peat followed a pseudo-second order rate equation. The chromium(III) could be easily eluted from the loaded peat using 0.10 M HCl and the peat may be reused in several sorption/ desorption cycles. The experimental results indicated the potential of Sphagnum moss peat for removal of Cr(III) from wastewaters.

Remediation of copper-contaminated topsoils from a wood treatment facility using in situ stabilisation

Five organic matters, three phosphate compounds, zerovalent iron grit (ZVIG, 2% by soil weight), two alkaline compounds, and two commercial formulations were incorporated, singly and some combined with ZVIG, into a highly Cu-contaminated topsoil (Soil P7, 2600 mg Cu kg(-1)) from a wood treatment facility. Formulations and two composts were also singly incorporated into a slightly Cu-contaminated topsoil (Soil P10, 118 mg Cu kg(-1)) from the facility surrounding. This aimed to reduce the labile pool of Cu and its accumulation in beans cultivated on potted soils in a climatic chamber. Lowest Cu concentration in soil solution occurred in P7 soils amended with activated carbon (5%) and ZVIG, singly and combined. Basic slag (3.9%) and compost of sewage sludge (5%) combined with ZVIG promoted shoot production and limited foliar Cu accumulation. For amended P10 soils, no changes occurred in soil solution and foliar Cu concentrations, but one compost increased shoot production.

Column study on the adsorption of Cr(III) and Cr(VI) using Pumice, Yarikkaya brown coal, Chelex-100 and Lewatit MP 62

In the present study, adsorption of Cr(III) and Cr(VI) on Pumice (Pmc), Yarikkaya (YK) brown coal, Chelex-100, and Lewatit MP 62 is examined at room temperature and at initial chromium concentration of 1.0 x 10(-3) mol/L. Column method was carried out as a function of pH, concentration of Cr(III) and Cr(VI) ions, volume of samples and flow rate. The experimental data were evaluated by Freundlich and Langmuir isotherm models. The dynamic breakthrough capacities of the adsorbents for Cr(III) and Cr(VI) were calculated. The maximum chromium sorption occurred at 5 mL/min flow rate and 25 mL volume for all adsorbents. The results showed that the two readily available adsorbents namely Pmc and YK, were suitable for removing chromium from aqueous solution.

Adsorption of Cd, Cu, Ni, Pb and Zn on Sphagnum peat from solutions with low metal concentrations

This work investigates adsorption of metal ions on Sphagnum peat from solutions with environmentally relevant concentrations of metals. The peat moss is intended as an alternative, low-cost filter material for contaminated waters. Adsorption of Cd, Cu, Ni, Pb and Zn was studied in batch tests, and adsorption isotherms were determined. The kinetics of adsorption was analyzed using a second-order model and rate constants were calculated. An empirical model for predicting adsorption of metal ions at a given time was derived from these constants. Metal ions were removed in the descending order Pb>Cu>Ni>Cd>Zn. Relationship between the affinities of the metals to the peat active sites with chemical properties for the metals were indicated by the results. In addition, equilibration studies were performed at constant pH and ionic strength. The experimental data fitted the Freundlich equation. Both the uptake of metals and the Freundlich constants increased in line with increasing pH. The Freundlich exponent declined with higher initial concentrations, suggesting adsorption to sites with lower activity.

Removal of methylene blue from aqueous solution by peat

In this study, the removal of methylene blue (MB) from aqueous solution by peat was analyzed. The peat was collected from a peatland at Arroio do Silva Beach, in Santa Catarina state, in the south of Brazil. Adsorption was conducted using varied initial concentrations of the MB solutions and three different temperatures (35, 45 and 60 degrees C). An adsorption time of around 4.5h was sufficient to reach the equilibrium for all temperatures, in the concentration range studied. Percentage removal was greater for diluted solutions, but the absolute amount of MB adsorbed by the peat at equilibrium increased with an increase of the initial concentration, corroborating the efficacy of the material as an adsorbent. Temperature influenced slightly the reaction, which was endothermic. Results indicated a multi-layered process and the data were analyzed considering pseudo-first-order, pseudo-second-order and intraparticle diffusion approaches. The latter two mechanisms seem to be significant in the rate-controlling step.

Effect of pH on cadmium biosorption by coconut copra meal

Biosorption of cadmium ion by coconut copra meal, an agricultural waste product was investigated as a function of initial solution pH and initial cadmium concentration. Pseudo-second-order kinetic analyses were performed to determine the rate constant of biosorption, the equilibrium capacity, and initial biosorption rate. Cadmium biosorption by copra meal was found to be dependent on the initial solution pH and initial cadmium concentration. Ion exchange occurred in the initial biosorption period. In addition, mathematical relationships were drawn to relate the change in the solution hydrogen ion concentration with equilibrium biosorption capacity, initial cadmium concentration, and equilibrium biosorption capacity.

Removal of cadmium from aqueous solutions by adsorption onto orange waste

The use of orange wastes, generated in the orange juice industry, for removing cadmium from aqueous solutions has been investigated. The material was characterized by Fourier transform infrared spectroscopy and batch experiments were conducted to determine the adsorption capacity of the biomass. A strong dependence of the adsorption capacity on pH was observed, the capacity increasing as pH value rose. Kinetics and adsorption equilibrium were studied at different pH values (4-6). The adsorption process was quick and the equilibrium was attained within 3h. The maximum adsorption capacity of orange waste was found to be 0.40, 0.41 and 0.43 mmol/g at pH 4-6, respectively. The kinetic data were analysed using various kinetic models - pseudo-first order equation, pseudo-second order equation, Elovich equation and intraparticle diffusion equation - and the equilibrium data were tested using four isotherm models - Langmuir, Freundlich, Sips and Redlich-Peterson. The data were fitted by non-linear regression and five error analysis methods were used to evaluate the goodness of the fit. The Elovich equation provides the greatest accuracy for the kinetic data and the Sips model the closest fit for the equilibrium data.

Equilibrium and kinetic modelling of chromium(III) sorption by animal bones

The paper discusses sorption of Cr(III) ions from aqueous solutions by animal bones. Animal bones were found to be an efficient sorbent with the maximum experimentally determined sorption capacity in the range 29-194 mg g(-1) that depended on pH and temperature. The maximum experimentally determined sorption capacity was obtained at 50 degrees C, pH 5. Batch kinetics and equilibrium experiments were performed in order to investigate the influence of contact time, initial concentration of sorbate and sorbent, temperature and pH. It was found that sorption capacity increased with increase of Cr(III) concentration, temperature and initial pH of metal solution. Mathematical models describing kinetics and statics of sorption were proposed. It was found that process kinetics followed the pseudo-second-order pattern. The influence of sorbent concentration was described with Langmuir-type equation and the influence of sorbate concentration was described with empirical dependence. The models were positively verified.