Biosorption of Metals and Metalloids

Ternary removal of Zn, Ni, and Mn from metal industry wastewater using soybean hulls as adsorbents

With the growth of the metalworking industry, effective control of wastewater with phosphate has become a global concern. This study took advantage of the abundant supply of natural soybean hulls as an adsorbent for the direct treatment of wastewater, aiming to remove Ni, Zn, and Mn from real wastewater produced during the phosphating stage of the metalworking industry to address this issue. Soybean hulls presented a specific surface area of 0.31 m2 g-1, average diameter of 0.2705 mm, and a pH value for PCZ of 6.43 at 25 °C. Real wastewater was acidic (pH 3.68) with COD of 1270 mg L-1 and highly concentrated in Ni, Mn, and Zn (343.45 mg L-1, 818.6 mg L-1, and 953.85 mg L-1, respectively). It was observed that the process depended on the adsorbent dosage, which can be linked to the low surface area of the material. The optimized pH value was found to be the natural pH of the effluent, which varied between 3 and 4. The average removal rates were 24.5% for Ni, 28.6% for Zn, and 16.5% for Mn, corresponding to the respective removal of 84.15, 135.07, and 272.80 mg L-1 in a ternary system. The maximum adsorption capacities were observed at 50 °C, estimated as 3.125 mg g-1 for Ni, 14.128 mg g-1 for Zn, and 7.8 mg g-1 for Mn. When evaluating the process kinetics, it was observed that adsorption capacity increased significantly during the initial 60 min, followed by a slower rate until saturation. The pseudo-first-order model provided the best fit for Ni adsorption, while Zn and Mn demonstrated the best fit with the pseudo-second-order model. This trend possibly occurred due to the different initial concentrations of each metal, which has shown to be a key factor in mass-driven adsorption mechanisms. Thus, using raw soybean hulls can be considered a viable alternative for coupling adsorption as a low-cost step to other treatment methods for metalworking wastewater.

Biohybrid Adsorbent for the Preconcentration of Lead and Its Determination in Fruit Juices by Electrothermal Atomic Absorption Spectrometry

BACKGROUND

Fruit juices are one of the most non-alcoholic beverages consumed in the world. Essential elements and other nutrients present in fruit juices play an important role in human well-being. However, fruit juices may also contain potentially toxic elements at trace levels, causing health risks.

OBJECTIVE

The objective of this work was to develop an analytical methodology based on the preconcentration of lead using a new biodegradable hybrid material (BHM) composed of Rhodococcus erythropolis AW3 bacteria and Brassica napus hairy roots.

METHODS

The BHM was implemented in an online solid-phase extraction (SPE) system for the determination of lead in fruit juices by electrothermal atomic absorption spectrometry (ETAAS).

RESULTS

Effects of critical parameters on lead retention were studied. Under optimal experimental conditions, extraction efficiency higher than 99.9% and an enrichment factor of 62.5 were achieved. The dynamic capacity of the BHM was 36 mg/g, which favored the reuse of the column for at least eight biosorption-desorption cycles. The LOD and LOQ for preconcentration of 5 mL of sample were 5.0 and 16.5 ng/L lead, respectively. The RSD was 4.8% (at 1 µg/L lead and n = 10).

CONCLUSION

The developed method was suitable for application to lead determination in different types of fruit juice.

HIGHLIGHTS

A novel microextraction procedure based on the use of a biohybrid adsorbent. Highly sensitive determination of Pb at trace levels. Analysis of Pb in fruit juices samples. An eco-friendly microextraction technique for Pb determination.

Novel bionanomaterial based on Spirulina maxima algae and graphene oxide for lead microextraction and determination in water and infant beverages

A new hybrid bionanomaterial composed of graphene oxide (GO) and Spirulina maxima (SM) algae was synthesized and applied to develop a preconcentration method based on the dispersive micro-solid phase extraction (D-μ-SPE) technique for the determination of Pb in water and infant beverages. In this work, Pb(II) was extracted with 3 mg of the hybrid bionanomaterial (GO@SM) followed by a back-extraction step using 500 µL of 0.6 mol L-1 HCl. Then, a 1.5 × 10-3 mol L-1 dithizone solution was added to the sample containing the analyte to form a purplish red-colored complex for its detection by UV-Vis spectrophotometry at 553 nm. An extraction efficiency of 98% was obtained after optimization of experimental variables such as GO@SM mass, pH, sample volume, type, and time of agitation. A detection limit of 1 μg L-1 and a relative standard deviation of 3.5% (at 5 μg L-1 Pb(II), n = 10) were achieved. The calibration linear range was obtained between 3.3 and 95 µg L-1 Pb(II). The proposed method was successfully applied for the preconcentration and determination of Pb(II) in infant beverages. Finally, the greenness degree of the D-µ-SPE method was evaluated using the Analytical GREEnness calculator (AGREE), obtaining a score of 0.62.

Treatment of textile wastewater using carbon-based nanomaterials as adsorbents: a review

Waste derived from the textile industry can contain a wide variety of pollutants of organic and inorganic natures, such as dyes (e.g., acid, basic, reactive, mordant dyes) and toxic metals (e.g., lead, chromium, cadmium). The presence of pollutants at high concentrations in textile waste makes them relevant sources of pollution in the environment. To solve this problem, various technologies have been developed for the removal of pollutants from these matrices. Thus, adsorption emerges as an efficient alternative for textile waste remediation, providing advantages as simplicity of operation, economy, possibility of using different adsorbent materials, and developing on-line systems that allow the reuse of the adsorbent during several adsorption/desorption cycles. This review will initially propose an introduction to the adsorption world, its fundamentals, and aspects related to kinetics, equilibrium, and thermodynamics. The possible mechanisms through which a pollutant can be retained on an adsorbent will be explained. The analytical techniques that offer valuable information to characterize the solid phases as well as each adsorbate/adsorbent system will be also commented. The most common synthesis techniques to obtain carbon nano-adsorbents have been also presented. In addition, the latest advances about the use of these adsorbents for the removal of pollutants from textile waste will be presented and discussed. The contributions reported in this manuscript demonstrated the use of highly efficient carbon-based nano-adsorbents for the removal of both organic and inorganic pollutants, reaching removal percentages from 65 to 100%.

Hybrid biomaterials to preconcentrate and determine toxic metals and metalloids: a review

Toxic elements represent a serious threat to the environment and cause harmful effects on different environmental components, even at trace levels. These toxic elements are often difficult to detect through the typical instrumentation of an analytical laboratory because they are found at very low concentrations in matrices such as food and water. Therefore, preconcentration plays a fundamental role since it allows the effects of the matrix to be minimized, thus reaching lower detection limits and greater sensitivity of detection techniques. In recent years, solid-phase extraction has been successfully used for the preconcentration of metals as an environmentally friendly technique due to the fact that it eliminates or minimizes the use of reagents and solvents and offers reduced analysis times and low generation of waste in the laboratory. Hybrid biomaterials are low-cost, eco-friendly, and useful as efficient solid phases for the preconcentration of elements. In this review, recent investigations based on the use of hybrid biomaterials for the preconcentration and determination of toxic metals are presented and discussed, given special attention to bionanomaterials. A brief description of hybrid biomaterials often used for analytical purposes, as well as analytical techniques mostly used to characterize the hybrid biomaterials, is explained. Finally, the future prospects that encourage the search for new hybrid biomaterials are commented upon.

A review on water treatment technologies for the management of oxoanions: prospects and challenges

Oxoanions are a class of contaminants that are easily released into the aquatic systems either through natural or anthropogenic activities. Depending on their oxidation states, they are highly mobile, resulting in the contamination of underground water. Above the permissible level in groundwater, they pose as threats to mammals when the contaminated water is consumed. Some of the health challenges caused are cancer, neurological, cardiac, gastrointestinal, and skin disorders. Several treatment technologies have been adopted over the years for the management of these oxoanions present in the aquatic systems. However interesting these treatment technologies might be, they also have their limitations such as cost-effectiveness, the complexity of the process, and generation of secondary pollutants. This work focused on some of the water treatment technologies applied for the removal of oxoanions. Some of the advantages and disadvantages of these treatment technologies are also highlighted. Amongst all the treatment technologies, adsorption is the most applied method for the removal of oxoanions. However, photocatalysis has a higher prospect since it is non-selective and secondary pollutants are not generated after the treatment process. Also, photocatalysis can simultaneously reduce and oxidise oxoanions as well as organic pollutants respectively.

Biomass-Derived Adsorbents for Dye and Heavy Metal Removal from Wastewater

Wastewater has a high concentration of dyes and heavy metals, which are the two most significant contaminants. Due to their high toxicity and vulnerability, they possess a potential threat to human health as well as the ecosystem. There are many ways to eliminate these pollutants from water but adsorption has attained much interest because of its low cost, easy application, and no secondary pollutants. Biomass is considered an ecological burden and a reason for the reduction in the earth’s carrying capacity. These materials may be used as cost-effective adsorbents to remove dyes and heavy metals from wastewater. This paper highlights recent advances made in dye and heavy metal adsorption in the last 10 years. The prime focus of this review paper is on the direct application of these biomasses without any chemical or physical alteration. The removal efficiencies and adsorption capabilities of different biomass-derived adsorbents for the removal of dyes and heavy metals from wastewater are summarised in this study. Additionally, the adsorption mechanisms underlying the removal of dyes and heavy metals using biomass-derived adsorbents have been discussed, with a focus on two kinetic models: pseudofirst-order and pseudosecond-order. Furthermore, the Langmuir and Freundlich isotherms were utilised to verify the experimental findings and to quantify the amount and degree of adsorption favorability. Based on what has been covered in the literature, the conclusion has been drawn. The future research needs are proposed in the area of biomass-derived adsorbent development, their modification for improved efficiencies, and application on large-scale wastewater treatment plants.