Biosorption of Pb(II) and Cd(II) ions by Agave sisalana (sisal fiber)

Efficient arsenic removal from water using iron-impregnated low-temperature biochar derived from henequen fibers: performance, mechanism, and LCA analysis

The present study aims to investigate the low-energy consumption and high-efficiency removal of arsenic from aqueous solutions. The designed adsorbent Fe/TBC was synthesized by impregnating iron on torrefaction henequen fibers. Isothermal adsorption experiments indicated maximum adsorption capacities of 7.30 mg/g and 8.98 mg/g for arsenic(V) at 25.0 °C and 40.0 °C, respectively. The interference testing showed that elevated levels of pH, HCO3- concentration, and humic acid content in the solution could inhibit the adsorption of arsenic by Fe/TBC. Characterization of the adsorbent before and after adsorption using FTIR and SEM-EDS techniques confirmed arsenic adsorption mechanisms, including pore filling, electrostatic interaction, surface complexation, and H-bond adhesion. Column experiments were conducted to treat arsenic-spiked water and natural groundwater, with effective treatment volumes of 550 mL and 8792 mL, respectively. Lastly, the life cycle assessment (LCA) using OpenLCA 2.0.3 software was performed to treat 1 m3 of natural groundwater as the functional unit. The results indicated relatively significant environmental impacts during the Fe/TBC synthesis stage. The global warming potential resulting from the entire life cycle process was determined to be 0.8 kg CO2-eq. The results from batch and column experiments, regeneration studies, and LCA analysis indicate that Fe/TBC could be a promising adsorbent for arsenic(V).

In Situ Growth of Nitrogen-Doped Fluorescent Carbon Dots on Sisal Fibers: Investigating Their Selective and Enhanced Adsorption Capabilities for Methyl Blue Dye

Preparing a biomass adsorbent material with high-absorption performance but low cost plays a vital role in wastewater treatment. In this study, a novel nitrogen-doped sisal fiber-based carbon dots (SF-N-CDs) composite was prepared by directly growing carbon dots (CDs) on sisal fiber (SF) using a microwave method with polyethyleneimine (PEI) as a raw material. The prepared SF-N-CDs were characterized using FTIR, XRD, Contact angle(CA), TGA, XPS, and SEM. The results revealed that the CDs were successfully grown on SF. The adsorption properties of SF-N-CDs were significantly enhanced when they adsorbed methyl blue (MeB) dye. Specifically, the adsorption of MeB by SF-N-CDs was up to 619.7 mg/g, which was about 2.6 times higher than that of raw SF. This implied that the introduction of CDs increases the adsorption site, thus enhancing the adsorption capacity. Analysis on kinetics and thermodynamics of MeB adsorption by SF-N-CDs revealed that the adsorption process followed the Langmuir isotherm model and were consistent with both kinetic models. It signifies that the adsorption involves both physical and chemical adsorption processes. Further, the SF-N-CDs maintained a removal rate of 70.9% after six adsorption-regeneration cycles, demonstrating good regeneration performance. Moreover, the SF-N-CDs could selectively separate MeB from a mixture of rhodamine B and saffron T. Consequently, the findings of this study suggest that SF-N-CDs are promising adsorbents for anionic dyes.

Adsorbents for water decontamination: A recycling alternative for fiber precursors and textile fiber wastes

The exponential growth in textile fiber production and commensurate release of textile waste-based effluents into the environment has significant impacts on human wellbeing and the long-term planetary health. To abate these negative impacts and promote resource circularity, efforts are being made to recycle these waste materials via conversion into adsorbents for water decontamination. This review critically examines plant- and regenerated cellulose-based fibers for removing water pollutants such as heavy metals, dyes, pharmaceutical and petrochemical wastes. The review reveals that chemical modification reactions such as grafting, sulfonation, carboxymethylation, amination, amidoximation, xanthation, carbon activation, and surface coating are normally employed, and the adsorption mechanisms often involve Van der Waals attraction, electrostatic interaction, complexation, chelation, ion exchange, and precipitation. Furthermore, the adsorption processes and thus the adsorption mechanisms are influenced by factors such as surface properties of adsorbents, pollutant characteristics including composition, porosity/pore size distribution, specific surface area, hydrophobicity/hydrophobicity, and molecular interactions. Besides, feasibility of the approaches in terms of handling and reuse, environmental fate, and economic impact was evaluated, in addition to the performances of the adsorbents, the prospects, and challenges. As current cost analysis is non-exhaustive, it is recommended that researchers focus on extensive cost analysis to fully appreciate the true cost effectiveness of employing these waste materials. In addition, more attention must be paid to potential chemical leaching, post-adsorption handling, and disposal. Based on the review, fiber precursors and textile fiber wastes are viable alternative adsorbents for sustainable water treatment and environmental management, and government entities must leverage on these locally accessible materials to promote recyclability and circularity.

Insights into the Applications of Natural Fibers to Metal Separation from Aqueous Solutions

There is a wide range of renewable materials with attractive prospects for the development of green technologies for the removal and recovery of metals from aqueous streams. A special category among them are natural fibers of biological origin, which combine remarkable biosorption properties with the adaptability of useful forms for cleanup and recycling purposes. To support the efficient exploitation of these advantages, this article reviews the current state of research on the potential and real applications of natural cellulosic and protein fibers as biosorbents for the sequestration of metals from aqueous solutions. The discussion on the scientific literature reports is made in sections that consider the classification and characterization of natural fibers and the analysis of performances of lignocellulosic biofibers and wool, silk, and human hair waste fibers to the metal uptake from diluted aqueous solutions. Finally, future research directions are recommended. Compared to other reviews, this work debates, systematizes, and correlates the available data on the metal biosorption on plant and protein biofibers, under non-competitive and competitive conditions, from synthetic, simulated, and real solutions, providing a deep insight into the biosorbents based on both types of eco-friendly fibers.

Evaluation of the Environmental Performance of Adsorbent Materials Prepared from Agave Bagasse for Water Remediation: Solid Waste Management Proposal of the Tequila Industry

In the present research work, the use of agro-industrial waste such as agave bagasse from the tequila industry was carried out. The agave bagasse was treated to obtain biosorbent and hydrochar materials. Direct Blue 86 was used as an adsorbate model to evaluate the performance of both materials. The adsorption studies showed an adsorption capacity of 6.49 mg g−1 in static and 17.7 mg g−1 in dynamic, associated with a physisorption process between functional groups of the material and the dye. The characterization of the biosorbent showed that the material was mainly composed of macroporous fibers with a surface area <5.0 m2 g−1. Elemental analysis showed a majority composition of C (57.19 wt%) and O (37.49 wt%). FTIR and XPS analyses showed that the material had C-O, C=O, -OH, O-C=O, and -NH2 surface groups. RAMAN and TGA were used to evaluate the composition, being cellulose (40.94%), lignin (20.15%), and hemicellulose (3.35%). Finally, the life-cycle assessment at a laboratory scale showed that the proposed biosorbent presents a 17% reduction in several environmental aspects compared to hydrochar, showing promise as an eco-friendly and highly efficient method for the remediation of water contaminated with dye, as well as being a promising alternative for the responsible management of solid waste generated by the tequila industry.

Facile preparation of sisal-Fe/Zn layered double hydroxide bio-nanocomposites for the efficient removal of rifampin from aqueous solution: kinetic, equilibrium, and thermodynamic studies

In the present study, sisal-Fe/Zn LDH bio-nanocomposite for efficiently removing rifampin was synthesized using a simple co-precipitation method. SEM, XRD, and FTIR analyses were applied to characterize the prepared composite. In the following, different factors that are affecting the adsorption of rifampin, including contact time, initial rifampin concentration, adsorbent dosage, and temperature were evaluated. Also, the kinetic, isotherm, and thermodynamic studies were investigated. The results indicated that Freundlich (R² = 0.9976) was a suitable model for describing the adsorption equilibrium and adsorption kinetic showed that the data are in maximum agreement with the pseudo-second-order kinetic model (R² = 0.9931). According to the Langmuir isotherm model, the maximum adsorption capacity of rifampin was found to be 40.00 mg/g. The main mechanisms for rifampin elimination were introduced as electrostatic attraction and physical adsorption. Moreover, the spontaneity and nature of the reaction were analyzed by elucidating thermodynamic factors that indicated the adsorption process was exothermic and spontaneous. Also, the batch process design indicated that for treating 10 L wastewater containing 100 mg/L rifampin with a removal efficiency of 96%, the needed amount of sisal-Fe/Zn LDH is 51.6 g. This study revealed that the sisal-Fe/Zn LDH bio-nanocomposites as a low-cost adsorbent have promising adsorption potential.

Efficient sequestration of lead from aqueous systems by peanut shells and compost: evidence from fixed bed column and batch scale studies

Lead (Pb) is a pervasive contaminant and poses a serious threat to living beings. The present study aims at batch and fixed bed column scale potential of commercial compost (CCB) and peanut shells biosorbents (PSB) for the sequestration of Pb from contaminated aqueous systems. The PSB and CCB were characterized with FTIR, SEM and Brunauer Emmett-Teller (BET) to get insight of the adsorption behavior of both materials. Fixed bed column scale experiments were performed at steady state flow (2.5 and 5.0 mL/min), initial Pb concentrations (25 and 50 mg/L) and dosage of each adsorbent (3.0 and 6.0 g/column). Columns packed (15.9 cm2) with PSB and CCB have revealed excellent adsorption of Pb with PSB as compared with CCB. The total volume of injected contaminated water was 1,500 mL and 3,000 mL at 2.5 and 5.0 mL/min, respectively while total bed volume number was 157. A series of batch experiments with CCB and PSB was conducted at adsorbent dosage (1.25–5.0 g/L), initial Pb level (25–100 mg/L), interaction time (0–180 min) and solution pH (4–10) at room temperature. Batch scale results revealed that PSB removed 92% Pb from water at 25 mg Pb/L concentration as compared with CCB (79%). The presence of competing ions in groundwater showed less Pb removal as compared with synthetic water. The experimental data were simulated with equilibrium isothermal models: Langmuir, Freundlich, and kinetic models: pseudo first order, pseudo second order and intra-particle diffusion. The Freundlich and pseudo second order models better described the equilibrium and kinetic experimental data, respectively with maximum sorption of 42.5 mg/g by PSB which is also evident from FTIR functional groups and SEM results. While equilibrium sorption of Pb onto CCB was equally explained by Freundlich and Langmuir models. These findings indicate that PSB could be an active and ecofriendly biosorbent for the sequestration of metals from contaminated aqueous systems.

Competitive and non-competitive zinc, copper and lead biosorption from aqueous solutions onto flax fibers

Competitive and non-competitive batch experiments were conducted on flax fibers to study Zn²⁺, Cu²⁺, and Pb²⁺ ions biosorption performance. Biosorption efficiency was dependent on contact time, pH, and biosorbent concentration. The results under competitive conditions were different from those obtained in non-competitive form. A high affinity of lead, with a selectivity sequence in general of Pb > Cu > Zn was observed. The biosorption data fitted very well the Langmuir model for lead in both types of solutions and for zinc and copper in the monometal form. The fit with the Freundlich model was not as successful, except for copper in the ternary system. Regarding zinc under competitive conditions, the sorption process was quite difficult and thus the equilibrium data could not fit well the adsorption models. The maximum adsorption capacities (mmol.kg^-1) were respectively 112, 122 and 71, for Pb, Cu and Zn in the single metal ion solution and 82, 57 and 8 only in the ternary, showing thus a high competition between metal ions when added simultaneously. Overall, lead could still be efficiently removed in spite of the presence of other ions while zinc would be overcome in the presence of lead and copper.

Determination of Cu, Ni, Mn and Zn in diesel oil samples using energy dispersive X-ray fluorescence spectrometry after solid phase extraction using sisal fiber

As a natural adsorbent, sisal (agave sisalana) fibers were used to extract Cu, Ni, Mn, and Zn from diesel oil samples for posterior determination (i.e., direct analytical measurements on the solid support) of the analytes by energy dispersive X-ray fluorescence spectrometry (EDXRF). In the proposed procedure, 0.2 g of sisal fiber was directly added to 5.0 mL of diesel oil contained in a glass tube. After 5 min of contact time, the mixture was filtered, and the collected fibers were oven-dried for 30 min at 70 °C. After drying, the analytes were quantified directly by EDXRF using the sisal fibers as a solid support. The calibration curves showed linear concentration ranges of 0.09-1.00, 0.12-1.00, 0.09-1.00, 0.06-1.0 μg g^-1 for Cu, Ni, Mn, and Zn, respectively. The limits of detection (LOD) for Cu, Ni, Mn, and Zn were 0.03, 0.04, 0.03, and 0.02 μg g^-1, respectively. The repeatability, evaluated by performing ten measurements at a concentration of 0.50 μg g^-1 for each metal, with the results expressed in terms of the relative standard deviation (RSD), was 3.2, 6.5, 6.8, and 6.1% for Cu, Ni, Mn, and Zn, respectively. The results obtained by the proposed method were compared with the results obtained by a comparative method using inductively coupled plasma optical emission spectrometry, and both results showed good agreement. The proposed method was applied for Ni, Cu, Mn, and Zn determination in diesel oil samples collected from different gas stations.

Comparative sorption isotherms and removal studies for Pb(II) by physical and thermochemical modification of low-cost agro-wastes from Tanzania

Corn and rice husks, agro-wastes available in large quantities in Tanzania, were used to remove Pb²⁺ from aqueous solution. Husks were used in raw form, pyrolyzed form, and chemically modified form. Material characterization was carried out using the BET method, FTIR spectroscopy, SEM, pH_PZC, and cation exchange capacity analysis. Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherms were used to elucidate Pb²⁺ sorption mechanisms. The surface area and cation exchange capacity (CEC) of untreated and chemically treated biochars were significantly higher than that of raw husks. Sorption data for Pb²⁺ for all biosorbents fit the Freundlich and D-R models well with high R² values. Most of the synthesized biosorbents in this study indicated >90% for Pb²⁺ removal, with the ZnCl₂-treated corn husk biochar sorption capacities ranking highest in all modeling results. Surface morphological features (e.g., micropores and fissures) and acidic and unsaturated functional groups may have significantly contributed to the observed Pb²⁺ removal efficiencies.

Investigation on the Performance of Chemically Modified Aquatic Macrophytes-Salvinia molesta for the Micro-Solid Phase Preconcentration of Cd(II) On-Line Coupled to FAAS

In this study, a new method for the preconcentration of cadmium ions using modified aquatic macrophytes - Salvinia molesta as biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. The method is based on preconcentration of 20.0 mL sample at pH 3.75 through 35.0 mg of biosorbent at 10.0 mL min^-1 and subsequent elution with 0.5 mol L^-1 HNO₃. A preconcentration factor of 31-fold, linear dynamic range from 5.0 to 70.0 µg L^-1 (r = 0.9996) and detection and quantification limits of 0.15 and 0.51 µg L^-1 were obtained. The characterization of the biosorbent chemically modified with NaOH and citric acid, was performed through FTIR and SEM measurements. The method precision was found to be 3.97 % and 1.48 % for 5.0 and 60.0 µg L^-1 Cd(II) solutions, respectively. The applicability of method was checked by analysis of different kind of water samples and certified reference material.

Removal of mercury(II) ions in aqueous solution using the peel biomass of Pachira aquatica Aubl: kinetics and adsorption equilibrium studies

Mercury is a highly toxic substance that is a health hazard to humans. This study aims to investigate powders obtained from the peel of the fruit of Pachira aquatica Aubl, in its in natura and/or acidified form, as an adsorbent for the removal of mercury ions in aqueous solution. The materials were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The infrared spectra showed bands corresponding to the axial deformation of carbonyls from carboxylic acids, the most important functional group responsible for fixing the metal species to the adsorbent material. The thermograms displayed mass losses related to the decomposition of three major components, i.e., hemicellulose, cellulose, and lignin. The adsorption process was evaluated using cold-vapor atomic fluorescence spectrometry (CV AFS) and cold-vapor atomic absorption spectrometry (CV AAS). Three isotherm models were employed. The adsorption isotherm model, Langmuir-Freundlich, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 0.71 and 0.58 mg g(-1) at 25 °C in nature and acidified, respectively. Adsorption efficiencies were further tested on real aqueous wastewater samples, and removal of Hg(II) was recorded as 69.6 % for biomass acidified and 76.3 % for biomass in nature. Results obtained from sorption experiments on real aqueous wastewater samples revealed that recovery of the target metal ions was very satisfactory. The pseudo-second-order model showed the best correlation to the experimental data. The current findings showed that the investigated materials are potential adsorbents for mercury(II) ion removal in aqueous solution, with acidified P. aquatica Aubl being the most efficient adsorbent.

Biosorption and Diffusion Modeling of Pb(II) by Malt Bagasse

The removal of Pb(II) from water by biosorption processes onto malt bagasse was investigated and the kinetic and thermodynamic parameters were obtained; additionally a diffusion modeling was proposed. The characterization of malt bagasse was performed by FTIR and SEM/EDS. The experiments were conducted in batch system and an experimental design based response surface methodology was applied for agitation speed and pH optimization. The kinetics of biosorption followed pseudo-second-order model and the temperature of the process affected the biosorption capacity. Isotherm models of Langmuir, Freundlich, and Elovich were applied and the Langmuir model showed better fit and the estimated biosorption capacity was 29.1 mg g−1. The negative values obtained for ΔG° and positive values of ΔH° confirm, respectively, the spontaneous and endothermic nature of the process. The diffusion modeling was performed based on experiments in the absence of agitation to investigate the influence of the biosorbent on the sorption process of Pb(II) ions.

The characteristics of waste Saccharomyces cerevisiae biosorption of arsenic(III)

PURPOSE

The potential of using waste Saccharomyces cerevisiae as adsorbent for the adsorption of As(III) from aqueous solution was assessed.

METHODS

The biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy analysis. Various parameters including pH, biosorbent dosage, contact time, and temperature were systematically investigated.

RESULTS AND CONCLUSIONS

The FTIR results of S. cerevisiae biomass showed that biomass has different functional groups, and these functional groups are able to react with metal ion in aqueous solution. Several biosorption isotherms were used to fit the equilibrium data, showing sorption to be monolayer on the heterogeneous surface of the biosorbent. The maximum biosorption capacity calculated using Langmuir model was found to be 62.908 μg/g at pH 5.0, biosorbent dosage 5 g/L, contact time 240 min, and temperature 35 °C. The kinetic studies indicated that the biosorption process of the As(III) followed well the pseudo-second-order equation. The intraparticle diffusion and Richenberg models were applied to the data, and we found that the biosorption of As(III) was governed by film diffusion followed by intraparticle diffusion. The thermodynamics constants indicated that the biosorption of As(III) onto S. cerevisiae was spontaneous and endothermic under examined conditions. Biosorbent could be regenerated using 0.5 M NaOH solution, with up to 75 % recovery.

Preconcentration and determination of copper in tobacco leaves samples by using a minicolumn of sisal fiber (Agave sisalana) loaded with Alizarin fluorine blue by FAAS

In the present study, a minicolumn of sisal fiber loaded with alizarin fluorine blue is proposed as a preconcentration system for copper determination in tobacco leaf samples by flame atomic absorption spectrometry. During the optimization procedure, a two level full factorial design (2(4)) was used at the preliminary evaluation of four factors, involving the following variables: sampling flow rate, elution flow rate, buffer concentration and pH. Regarding the studied levels, this design has shown that buffer concentration and pH were significant factors. The experimental conditions established in the optimization step were: pH=4.75, buffer concentration of 0.005 mol L(-1) for elution with HCl 1.0 mol L(-1) this system allows the determination of copper content with a detection limit (LD) of 0.018 μg L(-1) and a quantification limit (LQ) of 0.061 μg L(-1) precision expressed as relative standard deviation (R.S.D.) of 4.65 and 5.07%, utilizing concentration of 10 and 2.0 μg L(-1), respectively, and a preconcentration factor of 75, for a sample volume of 50.0 mL. Accuracy was confirmed by copper determination in the standard reference material, NIST SRM 1570 a trace element units in Spinach Leaves and by spike tests with recovery levels ranging from 93 to 100%; the procedure was applied for copper determination in tobacco leaf samples collected in Cruz das Almas City, Bahia, Brazil. The achieved concentrations of the three samples analyzed varied from 0.15 to 0.52 μg g(-1).