Heavy Metal Adsorption Capacity Research Articles

Effects of Gamma-Synthesized Chitosan on Morphological, Thermal, Mechanical, and Heavy-Metal Removal Properties in Natural Rubber Foam as Sustainable and Eco-Friendly Heavy Metal Sorbents

The properties of natural rubber foam (NRF) containing gamma-synthesized chitosan (CS) powder were investigated to address the growing demand for efficient methods to treat industrial wastewater contaminated with heavy metals. The CS powder was prepared by irradiating chitin (CT) powder with varying doses of gamma rays (0–100 kGy), followed by deacetylation using 40% sodium hydroxide (NaOH) at 100 °C for 1 h. The resulting CS powders were then mixed with natural rubber latex (NRL) at different contents (0, 3, 6, and 9 parts per hundred parts of rubber by weight; phr) and processed using Dunlop techniques to prepare the foam samples. The experimental findings indicated that the degree of deacetylation (%DD) of the CS powder increased initially with gamma doses up to 60 kGy but then decreased at 80 and 100 kGy. In addition, when the CS powder was incorporated into the NRF samples, there were increases in total surface area, density, compression set, and hardness (shore OO), with increasing gamma doses and CS contents. Furthermore, the determination of heavy metal adsorption properties for Cu, Pb, Zn, and Cd showed that the developed NRF sample exhibited high adsorption capacities. For instance, their removal efficiencies reached 94.9%, 82.5%, 91.4%, and 97.0%, respectively, in NRF containing 9 phr of 60 kGy CS. Notably, all adsorption measurements were determined using 3 cm × 3 cm × 2.5 cm specimens submerged in respective metal solutions, with an initial concentration of 25 mg/L. However, the removal capacity per unit mass of the sample (mg/g) showed less dependencies on CS contents, probably due to the higher density of CS/NRF composites in comparison to pristine NRF, resulting in a smaller volume of the former being submerged in the solution, subsequently suppressing the effects from CS in the adsorption. Lastly, tests on the reusability of the developed NRF indicated that the samples could be reused for up to three cycles, with the Cu removal capacity remaining relatively high (83%) in the sample containing 9 phr of 60 kGy CS. The overall outcomes implied that the developed NRF with the addition of gamma-synthesized CS not only offered effective and eco-friendly heavy metal adsorption capacity to improve public health safety and the environment from industrial wastewater but also promoted greener and safer procedures for the synthesis/modification of similar substances through radiation technologies.

Competitive sequestration behavior and mechanism of Cd2+, Pb2+and Ni2+ ions from single, binary and ternary metal laden solution by Hevea brasiliensis wood sawdust (HBS)

HeveaBrasiliensis wood sawdust (HBS), a lignocellulosic material, was employed for the eradication of Cd(II), Pb(II), and Ni(II) from synthetic single and multi-metalsystem. In the realm of multimetal adsorption, HBS exhibited the most substantial adsorption capacities for heavy metals, in the order: Pb(II) > Cd(II) > Ni(II). Experiments involving batch process were carried out to explore the rolesofpH, contact duration, HBS quantity, and preliminary metal concentrations on the adsorption capacity. Optimal conditions for biosorption of metal ions were determined as pH 5.0, dosage of 7 gL−1, and an equilibrium time of 90 min. The pseudo-second-order kinetics andLangmuirisotherm had a favorable alignment with the biosorption of all individual metal ions. Adsorption capacity was 8.45, 13.01 and 6.04 mg g− 1 for Cd, Pb and Ni respectively in single metal system. In binary and ternary system the capacity and adsorption percentages decreases significantly due the presence of competitive metal ions. HBS demonstrated effectiveness in treating real wastewater containing Cd2+, Pb2+and Ni2+ ionsin both single and mixed metal solutions, highlighting the necessity of thoroughly considering the impact of competitive adsorption. SEM with EDS results indicated single metal fixing in a multi-ion solution followed complex mechanisms. The surface area and functional group studies were conducted utilizing BET and a FTIR Spectrometer. Electrostatic attraction and complexation mechanisms were identified as responsible factor for capturing metal ions to the active surfaces of the bio sorbent. Cost analysis reflected the adsorbent cost was $0.021 per liter of mixed contaminated ternary effluent (30 mg L−1).

Mechanism of Biological Transport and Transformation of Copper, Cadmium, and Zinc in Water by Chlorella

This study investigates the effectiveness of Chlorella vulgaris in treating copper, cadmium, and zinc in aqueous solutions; the aim of this study was to examine the effects of various factors on the adsorption capacity of Chlorella in water. This study explored the intra- and extracellular adsorption and accumulation patterns of copper (Cu(II)), cadmium (Cd(II)), and zinc (Zn(II)), revealing their molecular response mechanisms under the most suitable conditions. The adsorption capacity of Chlorella to Cu(II), Cd(II), and Zn(II) in water was 93.63%, 73.45%, and 85.41%, respectively. The adsorption mechanism for heavy metals is governed by both intracellular and extracellular diffusion, with intracellular absorption serving as a supplement and external uptake predominating. XRD, XPS, FTIR, SEM-EDX, and TEM-EDX analyses showed that there would be the formation of precipitates such as Cu2S, CuS2, CdS, and ZnSO4. The adsorption of Cu(II) involves its simultaneous reduction to Cu(I). Moreover, specific functional groups present on the cellular surface, such as amino, carboxyl, aldehyde, and ether groups, interact with heavy metal ions. In view of its efficient heavy metal adsorption capacity and biosafety, this study recommends Chlorella as a potential biosorbent for the bioremediation and environmental treatment of heavy metal contaminated water in the future.

Hydrochar Production Methods: Comparative Insights into Hydrothermal and Microwave Processes

This study compares hydrochar production from agricultural waste using conventional hydrothermal carbonization (HTC) and microwave-assisted carbonization methods. Wheat straw (HWS), rice straw (HRS), and bagasse (HBG) were used as feedstocks. Microwave-assisted carbonization resulted in higher yields and distinct chemical structures compared to conventional HTC. Microwave hydrochars (m-HWS, m-HRS, mHBG) showed lower surface areas but increased pore volumes and thermal stability. They also exhibited enhanced heavy metal adsorption capacities, particularly at higher pH levels. These findings highlight the advantages of microwave-assisted carbonization for producing hydrochar with superior properties, offering insights for optimizing production processes and expanding applications.

Synthesis of CS-Fe3O4/GO nanocomposite for adsorption of heavy metal in aqueous environment

In this study, magnetic material based on graphene oxide (GO) was developed for enhanced adsorption capacity for heavy metals. The Fe3O4 nanoparticles were combined with the GO material using a chitosan (CS) binder to obtain the CS-Fe3O4/GO nanocomposite. The adsorption capacity of this nanocomposite was evaluated by removing heavy metals including Ni2+ ions. When GO was composed with Fe3O4 and CS, the GO films were densely covered with ferromagnetic particles, which were bound and densely distributed on the GO film surface due to the interaction between GO and CS. The optimal conditions for the complexation of Ni2+ and 4-(2-pyridyl azo)-rezoxine (PAR) are 1 ml Ni2+, 2 ml PAR 100 mg l−1, pH = 6 (adjusted with 0.7 ml of the 0.1 M K2HPO4 solution) and a complexation time of 20 min. After 50 min of adsorption, the Ni2+ removal efficiency of the CS-Fe3O4/GO nanocomposite reached 81.21% and the corresponding adsorption capacity was 2.03 mg g−1 . The Ni2+ removal process followed the first-order model and Freundlich isotherm. This process was spontaneous (ΔG o < 0) and an exothermic process (ΔH o = −1128.875 J·mol−1). In addition, the factors affecting this process were investigated, including the pH solution, the dosage of the CS-Fe3O4/GO nanocomposite and the initial Ni2+ concentration. The CS-Fe3O4/GO nanocomposite showed a potential adsorption capacity in removing Ni2+ at low concentrations from wastewater.

Synthesis of reduced graphene oxide and its application for the removal of anaionic dye TURQUOISE GN

Although graphene oxide (GO) and its derivatives showed excellent adsorption capacities for dyes and heavy metals, its application is limited to cationic and commercially used dyes. In this article reduced graphene oxide (RGO) was prepared and applied for the adsorption of a commercially used anionic dye. GO was prepared from graphite powder by modified Hummer’s method and reduced to RGO by hydrazine hydrate. Characterization of prepared RGO was carried out by Raman spectroscopy, ESEM, XRD, elemental analysis and the surface charge was determined by zeta potential analysis. An anionic dye TURQUOISE GN (TGN) was used to investigate the adsorption capacity of prepared RGO. To know the adsorption properties of RGO, the effects of solution pH, dosage of adsorbent, concentration of the dye, adsorption time and temperature on adsorption capacity of RGO were also studied. The distribution of the adsorbate on the RGO surface was studied with both Langmuir and Freundlich isotherm models and it was found that it preferably followed Langmuir model. The theoretical maximum adsorption capacity was found to be 588.24 mg/g at pH 7. To find out the mechanism of the adsorption of TGN on RGO pseudo-first-order and pseudo-second order kinetic models were applied and the results fitted perfectly with the second-order kinetic model. The exhausted RGO was regenerated by treating with 2 % HCl followed by washing with demineralized water and showed moderate adsorption capacity.

Study on Adsorption of Cd in Solution and Soil by Modified Biochar-Calcium Alginate Hydrogel.

Contamination with cadmium (Cd) is a prominent issue in agricultural non-point source pollution in China. With the deposition and activation of numerous Cd metal elements in farmland, the problem of excessive pollution of agricultural produce can no longer be disregarded. Considering the issue of Cd pollution in farmland, this study proposes the utilization of cross-linked modified biochar (prepared from pine wood) and calcium alginate hydrogels to fabricate a composite material which is called MB-CA for short. The aim is to investigate the adsorption and passivation mechanism of soil Cd by this innovative composite. The MB-CA exhibits a higher heavy metal adsorption capacity compared to traditional biochar and hydrogel due to its increased oxygen-containing functional groups and heavy metal adsorption sites. In the Cd solution adsorption experiment, the highest Cd2+ removal rate reached 85.48%. In addition, it was found that the material also has an excellent pH improvement effect. Through the adsorption kinetics experiment and the soil culture experiments, it was determined that MB-CA adheres to the quasi-second-order kinetic model and is capable of adsorbing 35.94% of Cd2+ in soil. This study validates the efficacy of MB-CA in the adsorption and passivation of Cd in soil, offering a novel approach for managing Cd-contaminated cultivated land.

Enhanced heavy metal adsorption capacity of surface-functionalized Philippine natural zeolite in simulated wastewater

The adsorption efficiency of surface-functionalized Philippine natural zeolite (PNZ) for heavy metal uptake from single and mixed metal ion-simulated wastewater solution is reported in this work. Atomic adsorption spectroscopy (AAS) findings revealed that NaCl-modified PNZ (MPNZ) exhibited the highest zinc ion adsorption of 99.96 % while PNZ yielded an adsorption of 95.61 %. The adsorption isotherms of raw PNZ and MPNZ both show similar shapes that reflect Type IV adsorption-desorption isotherms with Type H2 hysteresis loop which can be observed for micro-mesoporous materials (pore containing 2–50 nm). An increase in PNZ pore size from 10.11 nm to 13.36 nm for NaCl-PNZ and 15.59 for NaOH-PNZ is observed after alkaline treatment. EDS confirmed the decrease in Si/Al ratio from 4.02 to 3.76, indicative of possible higher negative charge in the PNZ framework which is favorable for an enhanced Coulombic or electrostatic interaction with the cationic heavy metals being detected in this study. MPNZ demonstrated an adsorption capacity of 99.96 % for copper in mixed-ion solution while 88.49 % and 86.67 % were obtained for zinc and nickel, respectively. These values are higher compared to PNZ having only 32.21 % uptake for zinc and 38.00 % for nickel. A hierarchy of the average metal adsorption capacity showed the order: copper > nickel > zinc. Rapid adsorption at the first hour of the adsorption reaction was attained in all solutions while samples with pH 9 exhibited the highest Ni2+ and Zn2+ percent removal. Moreover, the increase in initial solution concentration led to lower adsorption efficiency and the maximum uptake was attained at 100 ppm. The equilibrium data of adsorption and mechanism were suitably described by Langmuir isotherm model. With these, surface functionalization of PNZ has further enhanced its cationic adsorption capacity on heavy metals in both single and mixed-ion solution having promising potential for wastewater remediation.

Application and mechanism of carbonate material in the treatment of heavy metal pollution: a review.

Among the many heavy metal pollution treatment agents, carbonate materials show strong flexibility and versatility by virtue of their high adsorption capacity for heavy metals and the characteristics of multiple and simple modification methods. It shows good potential for development. This review summarizes the application of carbonate materials in the treatment of heavy metal pollution according to the research of other scholars. It mainly relates to the application of surface-modified, activated, and nano-sized carbonate materials in the treatment of heavy metal pollution in water. Natural carbonate minerals and composite carbonate minerals solidify and stabilize heavy metals in soil. Solidification of heavy metals in hazardous waste solids is by MICP. There are four aspects of calcium carbonate oligomers curing heavy metals in fly ash from waste incineration. The mechanism of treating heavy metals by carbonate in different media was discussed. However, in the complex environment where multiple types of pollutants coexist, questions on how to maintain the efficient processing capacity of carbonate materials and how to use MICP to integrate heavy metal fixation and seepage prevention in solid waste base under complex and changeable natural environment deserve our further consideration. In addition, the use of carbonate materials for the purification of trace radioactive wastewater and the safe treatment of trace radioactive solid waste are also worthy of further exploration.

Mesoporous Mg–Al–Ti composite oxide incorporated mixed matrix ultrafiltration membrane with superior multi-heavy metal removal capacity, anti-fouling & anti-microbial property

Mesoporous Mg–Al–Ti ternary composite oxide nano-adsorbents have demonstrated an exceptional performance to remove multiple heavy metals (As, Pb, Cd, Cr). Incorporation of these nanoparticles (NPs) in polysulfone membrane created a multifunctional mixed matrix membrane (MMM) with heavy metal adsorption capacity (both cationic and anionic species), enhanced hydrophilicity, anti-fouling property, and anti-microbial activity. The best heavy metal removal performance was shown by the membrane incorporated with 0.8 wt% NPs. Hydrophilicity improvement was studied through the decrease in water contact angle from 71° to 57° and surface probing using atomic force microscopy (AFM). With a maximum As(III) adsorption capacity of 256.6 mg/g, the membrane had a breakthrough volume of 25L and could provide safe drinking water for 19 h from a real Arsenic (As) contaminated groundwater sample with a flux of 48 l/m2-h. Beyond that, >90 % removal of Cd, Pb & Cr was also observed with maximum adsorption capacity of 652.9 mg/g, 332.5 mg/g, and 89.4 mg/g respectively. 92.5 % flux recovery after filtering a 1000 ppm bovine serum albumin showed the anti-fouling property. Successful inhibition of both gram-positive and gram-negative bacterial growth, and >99.99 % removal of colony forming units (CFU/ml) in the filtration process confirmed the anti-microbial resistance. With its multifunctionality, these membranes hold great potential for practical water treatment applications.

Machine learning-based prediction and experimental validation of heavy metal adsorption capacity of bentonite

As a natural adsorbent material, bentonite is widely used in the field of heavy metal adsorption. The heavy metal adsorption capacity of bentonite varies significantly in studies due to the differences in the properties of bentonite, solution, and heavy metal. To achieve accurate predictions of bentonite's heavy metal adsorption capacity, this study employed six machine learning (ML) regression algorithms to investigate the adsorption characteristics of bentonite. Finally, an eXtreme Gradient Boosting Regression (XGB) model with outstanding predictive performance was constructed. Explanation analysis of the XGB model further reveal the importance and influence manner of each input feature in predicting the heavy metal adsorption capacity of bentonite. The feature categories influencing heavy metal adsorption capacity were ranked in order of importance as adsorption conditions > bentonite properties > heavy metal properties. Furthermore, a web-based graphical user interface (GUI) software was developed, facilitating researchers and engineers to conveniently use the XGB model for predicting the heavy metal adsorption capacity of bentonite. This study provides new insights into the adsorption behaviors of bentonite for heavy metals, offering guidance and support for enhancing its application efficiency and addressing heavy metal pollution remediation.

Machine Learning Application to Optimize Spent Mushroom Compost (SMC) Biochar as Filter Media for Heavy Metal Adsorption in Abandoned Mine Water

AbstractThe surging global population strains resources, escalating pollution, and exacerbating water scarcity. Sustainable water management necessitates alternative sources such as abandoned mine water. However, these sources often contain hazardous heavy metals, like lead, copper, iron, and manganese, posing grave health and environmental risks. Conventional methods struggle to effectively treat these heavy metals in abandoned mining ponds, urging the search for cost‐efficient and sustainable solutions. Biochar, particularly from spent mushroom compost (SMC), emerges as a potent adsorbent due to its high surface area and binding groups. Yet, the variability in its efficiency remains a challenge. Conventional empirical models fail to capture the dynamic nature of adsorption processes accurately. Adopting machine learning, specifically an adaptive neuro‐fuzzy inference system (ANFIS), shows potential in predicting adsorption efficiency. This study aims to employ ANFIS to forecast SMC biochar's performance in a lab‐scale metal retention pond, providing design charts for diverse initial metal concentrations and pH levels. Validation through real cases aims to enhance accuracy and establish a framework for future heavy metal adsorption capacities. This research offers a sustainable approach to removing heavy metals from abandoned mining ponds whereas the computational modeling in optimizing SMC biochar introduces a novel approach for practical applications.

Activated nanosulfur for broad-spectrum heavy metals capture

Current problems of existing heavy metal-removing technologies, especially for nanomaterials-based ones, are typically single metal ion-specific, high-cost and collected difficult. Herein, facile modification of commercial sulfur creates a versatile adsorbent platform to address challenges. The versatile adsorbent can be easily prepared through solvothermal treatment of a saturated commercial sulfur solution, followed by water precipitation on a commercial foam that eliminates the need for separation. Interestingly, the solvothermal treatment endows the resulting nanosulfur with sulfate acid groups (hard Lewis base), sulfur anions (soft base), and sulfite groups (borderline base), promising the coordination of all types of heavy metal ions (Lewis acids). As such, this versatile adsorbent with well-distributed adsorption sites exhibits highly effective heavy metal adsorption capacity towards diverse heavy metal ions for both single-component and multi-component adsorption, including soft, hard, borderline Lewis metal ions, with ultra-high adsorption ability (e.g., 903.79 mg g−1 for Cu2+). These findings highlighted the potential of this low-cost sulfur-based adsorbent to address the arising challenges in ensuring clean water.

The application of machine learning methods for prediction of heavy metal by activated carbons, biochars, and carbon nanotubes

Carbonaceous materials are commonly used as adsorbents for heavy metals. The determination of the adsorption capacity needs time and energy, and the key factors affecting the adsorption capacity have not been determined. Therefore, a new and efficient method is needed to predict the adsorption capacity and explore the decisive factors in the adsorption process. In this study, three tree-based machine learning models (i.e., random forest, gradient boosting decision tree, and extreme gradient boosting) were developed to predict the adsorption capacity of eight heavy metals (i.e., As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) on activated carbons, biochars, and carbon nanotubes using 3674 data points extracted from 151 journal articles. After a comprehensive comparison, the gradient boosting decision tree had the best performance for a combined model based on all data (R2 = 0.9707, RMSE = 0.1420). Moreover, independent models were developed for three datasets classified by the adsorbent and eight datasets classified by the heavy metals. In addition, a graphical user interface was built to predict the adsorption capacity of heavy metals. This study provides a novel strategy and convenient tool for the removal of heavy metals and can help to improve the removal efficiency of heavy metals to build a healthier world.

Metabolomics-based analysis of the interaction effects and stress response mechanisms in the co-culture system of fungi and microalgae under cadmium stress

Research on the co-culture of fungi and microalgae to harvest microalgae and enhance the adsorption capacity for heavy metals to reduce contamination is well demonstrated, but the study of the correlation mechanism among critical metabolites, system stability, and stress response in the system under cadmium stress based on metabolomics analyses has not been reported in detail. In this study, the co-culture system of Aspergillus allahabadii and Synechocystis sp. PCC6803 was taken as the object of investigation, and isotope labelling (13C–Na2CO3 and 15N-(NH4)2SO4) and nanoscale secondary ion mass spectrometry were used to confirm the existence of carbon and nitrogen nutrient exchange. The adsorption behavior of the system after Cd treatment was investigated by Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy, and Scanning Electron Microscope/Transmission Electron Microscope. The content of extracellular polysaccharides in the system was increased from 40.8 mg/g to 80.12 mg/g, and the content of extracellular proteins was increased from 22.3 mg/g to 55.68 mg/g after 96 h of Cd treatment. Metabolomics results revealed 235 differential metabolites co-expressed after Cd treatment, with 95, 15, and 77 unique differential metabolites. In particular, the synthesis of extracellular polymeric substances was a factor affecting the stability of the symbiotic system, the up-regulation of the expression of the transporter system was one of the reasons for the improvement of the system's tolerance and resistance to heavy metals; and the nutrient metabolism between the fungus and the microalgae was the main defense mechanism to reduce the extent of the impairment of the system's carbon sequestration capacity by Cd. This provides a theoretical basis for the green and economically friendly application of the symbiotic system in microalgae harvesting, efficient carbon dioxide fixation and reduction of heavy metal pollution.

Study on the solidification performance and mechanism of heavy metals by sludge/biomass ash ceramsites, biochar and biomass ash.

Industrial by-products are stored in large quantities in the open, leading to wasted resources and environmental pollution, and the natural environment is similarly faced with phosphate depletion and serious water and soil pollution. This study uses these by-products to produce a new sludge/biomass ash ceramsite that will be used to adsorb nitrogen and phosphorus from wastewater, and solidify heavy metals in the soil while releasing Olsen P. The sludge/biomass ash ceramsites are made using sewage sludge and biomass ash in a certain ratio calcined at high temperatures and modified for the adsorption of nitrogen and phosphorus from wastewater. Sludge/biomass ash ceramsites before and after phosphorus adsorption, biochar and biomass ash were compared to analyze their heavy metal adsorption capacity and potential as phosphate fertilizer. After phosphorus adsorption, the sludge/biomass ash ceramsites released effective phosphorus steadily and rapidly in the soil, with a greater initial release than biochar and biomass ash, and the ceramsites were in a granular form that could be easily recycled. Biochar and biomass residue, due to their surface functional groups, are better at solidifying heavy metals than sludge/biomass ash ceramsites. Biochar, biomass ash and sludge/biomass ash ceramsites significantly reduced the concentrations of Cd, Cu, Pb and Zn in the soil. Correlation analysis demonstrated that there was a synergistic relationship between the increase in soil Olsen P content and the change in pH, with the increase in soil Olsen P content and the increase in pH contributing to heavy metal solidification.

Efficient and Selective Removal of Heavy Metals and Dyes from Aqueous Solutions Using Guipi Residue-Based Hydrogel.

The presence of organic dyes and heavy metal ions in water sources poses a significant threat to human health and the ecosystem. In this study, hydrogel adsorbents for water pollution remediation were synthesized using Guipi residue (GP), a cellulose material from Chinese herbal medicine, and chitosan (CTS) through radical polymerization with acrylamide (AM) and acrylic acid (AA). The characteristics of the hydrogels were analyzed from a physicochemical perspective, and their ability to adsorb was tested using model pollutants such as Pb2+, Cd2+, Rhodamine B (RhB), and methyl orange (MO). The outcomes revealed that GP/CTS/AA-co-AM, which has improved mechanical attributes, effectively eliminated these pollutants. At a pH of 4.0, a contact duration of 120 min, and an initial concentration of 600 mg/L for Pb2+ and 500 mg/L for Cd2+, the highest adsorption capabilities were 314.6 mg/g for Pb2+ and 289.1 mg/g for Cd2+. Regarding the dyes, the GP/CTS/AA-co-AM hydrogel displayed adsorption capacities of 106.4 mg/g for RhB and 94.8 mg/g for MO, maintaining a stable adsorption capacity at different pHs. Compared with other competitive pollutants, GP/CTS/AA-co-AM demonstrated a higher absorption capability, mainly targeted toward Pb2+. The adsorption processes for the pollutants conformed to pseudo-second-order kinetics models and adhered to the Langmuir models. Even after undergoing five consecutive adsorption and desorption cycles, the adsorption capacities for heavy metals and dyes remained above 70% and 80%. In summary, this study effectively suggested the potential of the innovative GP/CTS/AA-co-AM hydrogel as a practical and feasible approach for eliminating heavy metals and dyes from water solutions.

Isolation and Influence of Carbon Source on the Production of Extracellular Polymeric Substance by Bacteria for the Bioremediation of Heavy Metals in Santo Amaro City

The city of Santo Amaro (Bahia, Brazil) gained visibility among the scientific community due to the contamination of the Subaé River by lead and cadmium from the PLUMBUM Mineração e Metalurgia Ltda industry, on the banks of the river in 1956, which produced lead ingots The present work aimed to investigate the adsorption capacity of heavy metals (Pb and Cd) of EPS produced by bacterial species from the Subaé River, for possible future application of these biopolymers in bioremediation processes in areas impacted by the aforementioned heavy metals. Subaé river water was collected for physical-chemical analysis and bacterial isolation. It was verified that all isolated bacteria produced an expressive amount of Exopolysaccharide (EPS). Thus, the optimization of this production in different sugars (sucrose, glucose, and mannitol) and in three different pHs: 5.5; 6.5, and 7.5. All bacteria produced EPS in large quantities and the best sugar was sucrose at pH 7.5. In order to use the EPS for the bioremediation area, the adsorption test of lead and cadmium was carried out by the isolated EPS. 0.5 g of the EPS was dissolved in 50 ml of deionized water, then the solutions of metals, lead acetate, and cadmium sulfate (procedure performed separately) were incubated at 28 °C for 16 h after that period, and were centrifuged. Samples were filtered to separate the insoluble EPS and the filtrates obtained were used in the quantification of the metals by atomic absorption (FAAS- Flame Atomic Absorption Spectrometry). Bacillus spp., Bacillus cereus, Staphylococcus spp., and Serratiamarcescens, all showed tolerance to the tested metals, due to the efficiency in the adsorption capacity of the EPS, and it was possible to distinguish seven genera, Klebsiella pneumonia, Pseudomonas aeruginosa, Lysinibacillus spp. to be used in the bioremediation of environments contaminated with heavy metals.

Textile waste valorization as potential activated carbon precursor for the removal of water contaminants: Commentary

Textile waste has become a global concern as its generation is increasing at an alarming rate. Various ways to manage and reduce textile waste are currently being sought, including reutilization and conversion into value-added products, to diversify its usage in an effort to minimize its environmental impact. Recent trends have shown the potential of textile waste as low-cost adsorbent for wastewater treatment applications. This paper aims to highlight the activation methods to convert textile waste into activated carbon and discuss its textural characteristics and performance in water contaminants removal. Data from literature showed promising high adsorption capacities of heavy metals, dyes, and pharmaceuticals by textile waste-derived activated carbons. Overall, the valorization of textile waste into activated carbon is generally feasible. Also, the superior surface chemistry and textural properties are imperative towards the exceptional performance of textile waste activated carbon in wastewater treatment applications.

Mathematical Models for Adsorption Capacity and Percent Removal of Heavy Metals from Water Using Stat-Ease 360

Heavy metal removal using adsorbent materials like watermelon rind, as investigated herein, will ensure a safe drinking water for consumption. For the first time, mathematical models taking A = adsorbent dosage, B = contact time and C = initial concentration as input variables were developed using Stat-Ease 360 design of experiment (DOE) tool for adsorption capacity (R1) and percent removal of heavy metals including, arsenic, cadmium, chromium, copper and lead (R2) in water, as two sole output variables. The models generated based on existing experimental observations (A, B, C) can be used to predict the responses or outputs of the adsorption process, especially looking at their respective satisfactory statistical performance parameters obtained. Several 3D surface and contour plots reveal the optimal factor combination for peak response performance for a particular metallic contaminant in the water. Optimal values for arsenic removal are 0.1g A, 120 min B, 3.12 mg/g R1 and 100% R2. Those of other metals present are as follows: 0.1g A, 60 min B, 0.17 mg/L C, 144.75 mg/g R1 and 85.78% R2 for cadmium; 0.1-1.2g A, 0&lt;B≤120 min, 0.028 mg/L C, 215 mg/g R1 and 85.53% R2 for chromium; 0.1-1.2g A, 0&lt;B≤120 min, 0.041 mg/L C, 275 mg/g R1 and 80% R2 for copper and; 0.1-1.2g A, 0&lt;B≤120 min, 0.029 mg/L C, 205 mg/g R1 and 83.42% R2 for lead. This study falls short of many heavy metals such as zinc, nickel, cobalt, antimony, iron and mercury removal used to test the effect of other factors like pH, presence of co-existing ions, temperature and sorbent particle size for their adsorption performance.