Multi-pollutant biosorption of organic and inorganic pollutants by brown algae waste from alginate production: batch and fixed-bed investigation.

The reuse of biomass waste has been gaining attention in adsorption processes to remove pollutants of emerging concern from water and wastewater. In this work, the potential of alginate-extracted macro-algae waste to uptake synthetic dyes and metal cations was evaluated in comparison with raw algae. In affinity assays, both materials were able to remove metal cations and cationic dyes up to maximum rates, and no significant removal was observed for an anionic dye in an acidic medium. Competition was observed in multi-component systems of metal cations and dyes. For binary samples containing organic and inorganic contaminants, kinetic modeling evidenced the distinct nature of both types of adsorbates. Pb(II) biosorption was best described as a first-order process, while second-order and Elovich models better fitted methyl blue (MB) uptake data. For equimolar binary samples, the Sips isothermal model fitted the experimental data more satisfactorily at room temperature. Isotherms for 20, 30, 40, and 60 °C exhibited favorable adsorption profiles with spontaneous ΔG values for both raw macro-algae and waste from alginate extraction. Maximum adsorption capacities were competitive with previous reports in the literature for a wide range of biomaterials, pointing to the slightly higher efficiency with algae waste in batch experiments. In elution tests, HNO3 (0.5 M) showed the best recovery rates of metal cations. Continuous biosorption operation revealed the performance of the brown algae waste was considerably more efficient than raw algae with breakthrough biosorption capacities up to 3.96 and 0.97 mmol.g-1 for the removal of Pb(II) and MB, respectively. A total of 3.0 g of algae and algae waste were able to deliver 1.20 and 1.62 L of contaminant-free water, respectively. XPS analyses corroborate previous assays that pointed to the prevalence of physisorption with evidence of complexation, ionic exchange, and hydrogen displacement mechanisms.

Binary adsorption isotherms of methylene blue and crystal violet on mandarin peels: prediction via detailed multivariate calibration and density functional theory (DFT) calculations.

The multicomponent adsorption of synthetic dyes has great relevance in the treatment of effluents due to the complexity of the adsorbate-adsorbent interactions. Therefore, this study provides useful information about the adsorption capacity of methylene blue (MB) and crystal violet (CV) in a bioadsorbent (mandarin peels) in a single-component and competitive system using detailed multivariate calibration analysis. The PLS1 multivariate calibration model was used to quantify the adsorbates. In mono and two-component systems, the adsorption capacity of CV (1.26-1.36 mg g-1) was superior when compared to MB (0.925-0.913 mg g-1), characterizing synergistic adsorption for CV and antagonistic adsorption for MB. The Sips model was effective for describing single-component systems, suggesting that adsorption did not occur in the monolayer. For competitive adsorption, modified, unmodified, and extended models were used to understand the interactions between the dyes and the bioadsorbent. The modified Redlich-Peterson (MRP) model was effective in describing the behavior of the binary system, indicating that the interaction forces with the adsorbate were significant. Thus, the bioadsorbent showed promising results for competitive adsorption, thus being of relevance to the industrial sector. Density functional calculations were also performed to characterize the atomic interactions for the removal of both dyes on mandarin peels.

Efficient removal of glyphosate from aqueous solutions by adsorption on Mg-Al-layered double oxides: thermodynamic, kinetic, and mechanistic investigation.

Up to 90% of glyphosate was removed in 40 min by a 2:1 Mg2Al-layered double oxide (LDO) at pH 10, and the adsorption kinetics fitted a pseudo-second-order law. The adsorption isotherms were type L, and the Langmuir model best fitted the experimental data, with qmax of 158.22 µg/mg at 25 °C. The intraparticle diffusion model suggested that the adsorption process is dependent on the thickness and formation of the film at the solution/solid interface. The XRD results excluded the intercalation of glyphosate anions, and FTIR along with solid-state 13C and 31P MAS NMR confirmed that the glyphosate anions interact through the carboxylate and/or phosphonate moieties, both in end-on and side-on modes to the LDO surface. Glyphosate removal was also investigated in the presence of different anionic species, and simultaneous adsorption showed that carbonate and phosphate ions strongly influence glyphosate removal.

Multi-component adsorption study by using bone char: modelling and removal mechanisms.

Highly efficient simultaneous removal of paracetamol and Cu2+ ions from aqueous solutions was accomplished by using bovine bone char (BC). The adsorption behaviour was determined by kinetic and equilibrium studies of both single and binary system solutions. BC is a predominantly mesoporous material with a surface area of 103 m2 g-1. The influence of the initial pH on Cu2+ removal was tested, suggesting that the optimal pH was 3.0. The removal of paracetamol from single and binary systems was 9.45 and 12.7%, respectively. On the other hand, the Cu2+ removal was 36.2% for a single system, suggesting a higher affinity for BC. Moreover, in the case of binary mixtures, the presence of paracetamol led to an enhanced affinity of Cu2+ due to a synergistic/cooperative mechanism, which led to a copper removal of 97.3%. The cooperative model was successfully adjusted to the equilibrium data of the binary systems. The modelling results indicated the formation of a first adsorption layer where paracetamol and copper are retained, and a second layer with a great affinity for copper ions after the formation of a Cu-paracetamol complex, leading to higher removal of Cu2+.

A review on the use of lignocellulosic materials for arsenic adsorption.

In this review, bibliometric analysis was made of recent studies and current trends concerning the application of lignocellulosic materials as bioadsorbents for the removal of arsenic from aqueous systems. Evaluation was made of lignocellulosic adsorbents and their chemical characteristics, as well as interactions involved in the adsorption of arsenic, bioadsorbent reusage (desorption and re-adsorption), competition between co-existing ions in multi-element aqueous solutions, and applications of bioadsorbents in batch and continuous systems. Lignocellulosic biomass has been shown to be a promising source of new adsorbents, since it is a low-cost and renewable material. However, there seems to be no commercially available technology that uses bioadsorbents based on lignocellulosic biomass for arsenic removal. In addition, the structural modification of lignocellulosic biomass to improve its adsorption capacity and selectivity has proved to be a suitable strategy, with the service time and the selectivity of the bioadsorbent in the presence of co-existing ions the most critical aspects to be pursued. The competitive adsorption of co-existing anions (PO43-, SO42-, NO3-, and Cl-) by the adsorption sites, as well as life-cycle assessment and cost analysis are rarely reported. Complexation, electrostatic attraction, ion exchange and precipitation were the main interactions involved in the adsorption of arsenic on lignocellulosic materials. However, most studies have failed to prove the nature of the interactions. Macroscopic methods can be useful to evaluate the adsorption mechanism of arsenic on bioadsorbents of complex structure, such as lignocellulosic biomass (modified or not). Nevertheless, the elucidation of the adsorption mechanism requires experiments based on measurements at the microscopic level. The upscaling of biosorption technology for arsenic removal will only be possible through studies that investigate: i) the interactions involved in the adsorption process; ii) the transfer of bench-scale experiments to pilot-scale experiments with real contaminated water with low arsenic concentration; and iii) the life-cycle assessment of biosorbents produced from lignocellulosic biomass.

Efficient and selective removal of SeVI and AsV mixed contaminants from aqueous media by montmorillonite-nanoscale zero valent iron nanocomposite.

Nanoscale zero-valent iron (NZVI) and NZVI supported onto montmorillonite (NZVI-Mt) were synthetized and used in this study to remove SeVI and AsV from water in mono- and binary-adsorbate systems. The adsorption kinetics and isotherm data for SeVI and AsV were adequately described by the pseudo-second-order (PSO) (r2>0.94) and Freundlich (r2>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L-1 AsV and SeVI concentration, the maximum adsorption capacity (qmax) and partition coefficient (PC) for AsV on NZVI-Mt in monocomponent system were 54.75 mg g-1 and 0.065 mg g-1·µM-1, which dropped respectively to 49.91 mg g-1 and 0.055 mg g-1·µM-1 under competitive system. For SeVI adsorption on NZVI-Mt in monocomponent system, qmax and PC were 28.63 mg g-1 and 0.024 mg g-1·µM-1, respectively. Values of qmax and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for AsV. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt.

Aminated cellulose as a versatile adsorbent for batch removal of As(V) and Cu(II) from mono- and multicomponent aqueous solutions.

A bioadsorbent (CEDA) capable of adsorbing As(V) and Cu(II) simultaneously was prepared by tosylation of microcrystalline cellulose (MC) and nucleophilic substitution of the tosyl group by ethylenediamine. MC, tosyl cellulose, and CEDA were characterized by elemental C, H, N, and S analysis, infrared spectroscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The adsorption of As(V) and Cu(II) on CEDA was evaluated as a function of solution pH, contact time, and initial solute concentration. The maximum adsorption capacities of CEDA for As(V) and Cu(II) were 1.62 and 1.09 mmol g-1, respectively. The interactions of As(V) and Cu(II) with CEDA were elucidated using thermodynamic parameters, molecular quantum mechanics calculations, and experiments with ion exchange of Cd(II) by Cu(II), and As(V) by SO42-. Adsorption enthalpies were determined as a function of surface coverage of the CEDA, using isothermal titration calorimetry, with ΔadsH° values of -32.24 ± 0.07 and -93 ± 2 kJ mol-1 obtained for As(V) and Cu(II), respectively. The potential to reuse CEDA was evaluated and the interference of other ions in the adsorption of As(V) and Cu(II) was investigated. Multi-component experiments showed that Cd(II), Co(II), Ni(II), and Pb(II) did not interfere in the adsorption of Cu(II), while SO42- inhibited As(V) adsorption.

Simultaneous biosorption of Cd(II), Ni(II) and Pb(II) onto a brown macroalgae Fucus vesiculosus: Mono- and multi-component isotherms, kinetics and thermodynamics.

Due to the anthropic activities, several heavy metal ions are introduced into the environment, impacting ecosystems and local activities. In this context, the biosorption process using algae represents an alternative form for these compounds remediation due to the advantages derived from the biosorbent and process efficiency. Thus, the present study evaluated Cadmium (Cd(II)), Nickel (Ni(II)) and Lead (Pb(II)) remediation from aqueous media in mono- and multi-component systems. The biosorbent was characterized in terms of its morphology and composition and parameters involving equilibrium, kinetics, and thermodynamics were investigated. Lastly, the sample was considered in a real surface water sample remediation impacted by a mining dam rupture. Except for Freundlich, all isotherm models tested satisfactorily adjusted to the experimental data for a mono-component system. The maximum biosorption capacities (qm) were 143.2 ±â€¯7.5, 70.1 ±â€¯1.9, 516.3 ±â€¯12.5 mg g-1 for Cd(II), Ni(II) and Pb(II) ions, respectively. When binary systems were considered, an antagonism effect was observed. The biosorption of Cd(II) was drastically affected by the presence of Ni(II), while Pb(II) biosorption in general was less affected by other metals presence. As observed for the binary system, the worst effect in the ternary system was observed for Cd(II) biosorption, being significantly affected by Ni(II) and Pb(II) presence. Overall, the biosorption order in mono- and multi-component systems was found to be Pb(II) ≫ Cd(II) > Ni(II). The affinity for the metals ions was also observed by Elovich's desorption constant, in which aPb(II)≪aCd(II)aCd(II), achieving an equilibrium passed 49 min. From the stages involved in biosorption process, film diffusion presented the greatest contribution as control-stage obtaining a lower diffusion coefficient in all cases. The process was spontaneous in all temperature range evaluated, considered exothermic for all metal ions evaluated. Iron, manganese and nickel concentrations in real surface water samples were higher than the allowed by the Brazilian National Environment Council (CONAMA). Comparing the hazard index values before and after the biosorption process, a reduction superior to 8 × was observed (HIbefore: 3.36, HIafter: 0.40), in which there was no non-carcinogenic risk imposed to the surrounding population after the treatment applied.

Adsorption study of heavy metals in aqueous solutions aiming at the treatment of contaminated groundwater.

This study evaluates the application of the vegetal activated carbon (AC), vegetable AC impregnated with Ag and Cu (0.08% m/m) and cationic SupergelTM SGC650H resin for adsorption of Fe3+ and Pb2+ ions in closed and batch system. The best adsorption capacities were obtained by using the cationic resin SGC650H, pH 3, temperature of 30 °C and stirring speed of 100 rpm. Thus, the kinetic and equilibrium experiments, in mono- and bicomponent, were performed using SGC650H resin, wherein the kinetic models of pseudo-first and pseudo-second order presented a good fit to the kinetic data, for mono- and bicomponent, respectively. The Langmuir isotherm adequately represented the monocomponent equilibrium data, showing maximum adsorption capacities values of 7.18 and 4.00 meq g-1 for Fe3+ and Pb2+, respectively. An inhibitory effect between the metal species was verified by fitting the modified extended Langmuir isotherm model to the binary equilibrium data, which allowed to predict changes in the surface affinity to the adsorbent by the metal ions. Based on the observed results, the use of SGC650H resin presents great potential for water treatment systems contaminated with heavy metals.

Synthesis and application of a new carboxylated cellulose derivative. Part II: Removal of Co2+, Cu2+ and Ni2+ from bicomponent spiked aqueous solution.

In the second part of this series of studies, the competitive adsorption of three binary systems Cu2+-Co2+, Cu2+-Ni2+ and Co2+-Ni2+ on a carboxylated cellulose derivative (CTA) was evaluated in binary equimolar (1:1) metal-ion aqueous solutions. Bicomponent adsorption studies were developed as a function of contact time and initial metal ion concentration. Bicomponent adsorption kinetic data was modeled by monocomponent kinetic models of pseudo-first- (PFO) and pseudo-second-order (PSO) and a competitive kinetic model of Corsel. Bicomponent adsorption isotherm data was modeled by the ideal adsorbed solution theory (IAST) and real adsorbed solution theory (RAST) models. The monocomponent isotherm models implemented into the IAST were the Langmuir and Sips models, whereas for the RAST model only the Langmuir model was implemented because this model provided the best prediction of the bicomponent isotherm data. The surface of the CTA adsorbent after bicomponent adsorption of metal ions was also examined by SEM-EDX. The effect of one metal ion on the adsorption capacity of another metal ion was discussed in detail with basis on the kinetic and thermodynamics parameters. The selectivity and performance of the CTA adsorbent for the removal of Cu2+, Co2+ and Ni2+ was also evaluated and discussed.

Single and multi-component adsorptive removal of bisphenol A and 2,4-dichlorophenol from aqueous solutions with transition metal modified inorganic-organic pillared clay composites: Effect of pH and presence of humic acid.

Pillared clay based composites containing transition metals and a surfactant, namely MAlOr-NaBt (Bt=bentonite; Or=surfactant; M=Ni(2+), Cu(2+)or Co(2+)), were prepared to study selectivity and capacity toward single and multiple-component adsorption of bisphenol A (BPA) and 2,4-diclorophenol (DCP) from water. Tests were also performed to account for the presence of natural organic matter in the form of humic acid (HA). Equilibrium adsorption capacities for single components increased as follows: NaBt

Negligible effects of tryptophan on the aflatoxin adsorption of sodium bentonite.

The main objective of this study was to determine if the competitive adsorption of tryptophan (Trp) and aflatoxin B1 (AFB1) could potentially affect the ability of a sodium bentonite (NaB) to prevent aflatoxicosis in monogastric animals. The adsorption of Trp and AFB1 on this adsorbent is fast and could be operating on the same time-scale making competition feasible. In vitro competitive adsorption experiments under simulated gastrointestinal conditions were performed. A high affinity of the clay for Trp and NaB was observed. The effect of an excess of KCl to mimic the ionic strength of the physiological conditions were also investigated. A six-times decrease in the Trp surface excess at saturation was observed. A similar behaviour was previously found for AFB1 adsorption. Taking into account the amount of Trp adsorbed by the clay and the usual adsorbent supplementation level in diets, a decrease in Trp bioavailability is not expected to occur. Tryptophan adsorption isotherms on NaB were 'S'-shaped and were adjusted by the Frumkin-Fowler-Guggenheim model. The reversibility of the adsorption processes was investigated in order to check a potential decrease in the ability of NaB to protect birds against chronic aflatoxicoses. Adsorption processes were completely reversible for Trp, while almost irreversible for AFB1. In spite of the high affinity of the NaB for Trp, probably due to the reversible character of Trp adsorption, no changes in the AFB1 adsorption isotherm were observed when an excess of the amino acid was added to the adsorption medium. As a consequence of the preferential and irreversible AFB1 adsorption and the reversible weak binding of Trp to the NaB, no changes in the aflatoxin sorption ability of the clay are expected to occur in the gastrointestinal tract of birds.