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Currently, the world faces difficulties related to the quantity and quality of water because of industrial expansion, population growth, and urbanization intensification. Biosorption is considered a promising technology that can be applied to remove toxic metals (TMs) and rare-earth metals (REMs) in wastewater at low concentrations, due to its efficiency and low cost. In this work, we investigated different non-conventional biosorbents to remove metallic ions (TMs and REMs) in biosorptive affinity tests. Metallic affinity assays among lanthanum and different biosorbents showed that greater affinities were found for sericin-alginate beads crosslinked with polyvinyl alcohol (SAPVA) (0.280 mmol/g) and polyethylene glycol diglycidyl ether (SAPEG) (0.277 mmol/g), expanded vermiculite (0.281 mmol/g), Sargassum filipendula seaweed (0.287 mmol/g), and seaweed biomass waste (0.289 mmol/g). Among the biosorbents evaluated, SAPVA and SAPEG beads, besides to sericin-alginate beads crosslinked with proanthocyanidins (SAPAs) were selected for affinity assays with other REMs and TMs. Compared to other particles, SAPVA beads showed higher potential for biosorption by REMs with the following order of affinity: Yb3+ > Dy3+ > Nd3+ > Ce3+ > La3+. Additionally, the biosorptive affinity of TMs by SAPVA beads followed the order: Al3+ > Cr3+ > Pb2+ > Cu2+ > Cd2+ > Zn2+ > Ni2+. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Removal of water pollutants (methylene blue dye and heavy metals) was achieved by zinc/manganese-doped nickel ferrites (Ni1 − xMxFe2O4, where x = 0.00, 0.025, 0.10). Degradation of dye was achieved under natural solar light illumination. Degradation studies of dye were conducted under different parameters such as contact time—80 min, dye's concentration—5 mg/L, pH—7, and dosage of ferrites—15 mg. The adsorption of dye was studied using non-linear kinetics models (pseudo-first-order and pseudo-second-order) and isotherm models (Langmuir and Freundlich). The adsorption of dye followed pseudo-first-order kinetics (R2 = 0.99377) than second-order kinetics (R2 = 0.98063) and Langmuir isotherm model (R2 = 0.96095) than Freundlich model (R2 = 0.95962) with maximum adsorption efficiency of 29.62 mg/g. Doping of nickel ferrites caused an increase in the removal percentage of methylene blue dye (80 to 90%) and inorganic effluents (75 to 95% for lead and 47 to 82% for cadmium). In addition to this, band gap energy (2.43 to 3.26 eV) (UV–Vis spectroscopy), pore radius (65.2 to 74.8 A°), and specific surface area (16.45 to 27.95 m2/g) (BET analysis) were also increased. Generally, the results of the study revealed that synthesized nanoparticles can act as potential candidate for the removal of effluents from wastewater under optimum parameters along with recyclability, reusability, and separation under the influence of a magnetic field. [ABSTRACT FROM AUTHOR]

Biochar has a large specific surface area, well-developed pore structure, abundant surface functional groups, and superior nutrient supply capacity, which is widely available and environmentally friendly with its advantages in waste resource utilization, heavy metal(loid) remediation, and carbon storage. This review focuses on the interactions between biochar (including raw biochar, functional biochar (modified/ engineered/ designer biochar), and composite biochar) and rhizosphere during the remediation of soil contaminated with heavy metal(loid)s (Pb, As, Cd, Hg, Co, Cu, Ni, Zn, Cr, etc.) and the effects of these interactions on the microbial communities and root exudates (enzymes and low-molecular-weight organic acids (LMWOAs)). In terms of microorganisms, biochar affects the composition, diversity, and structure of microbial communities through the supply of nutrients, provision of microbial colonization sites, immobilization of heavy metal(loid)s, and introduction of exogenous microorganisms. With regard to root exudates, biochar provides electron transfer support between the microorganisms and exudates, regulates the secretion of enzymes to resist the oxidative stress stimulated by heavy metal(loid)s, ameliorates rhizosphere acidification caused by LMWOAs, and promotes the activity of soil enzymes. The roles and mechanisms of biochar on rhizosphere soils are discussed, as well as the challenges of biochar in the remediation of heavy metal(loid)-contaminated soils, and the issues that need to be addressed in future research are foreseen. Highlights: The interactions between biochar and rhizosphere in the remediation of soil with heavy metal(loid)s have been focused Biochar affects rhizosphere microorganisms by changing population diversity and community structure Biochar regulates root exudates secretion and promotes soil enzyme activity in contaminated soil [ABSTRACT FROM AUTHOR]

Due to the different physical and chemical properties such as surface charge and ion morphology between As(V) and Cd(II), it is challenging to remove As(V) and Cd(II), especially at low concentrations. This study constructed a novel three-dimension nanocomposite adsorbent Mg/Al/Fe-CLDH (CFMA) by "hydrothermal + calcination method". And different initial concentration ratios (Cd: As=1: 2, 1: 1, 2: 1) were used to investigate the removal performance of CFMA for Cd(II) and As(V). When the concentration ratio Cd: As=1: 2, the residual concentrations of As(V) and Cd(II) were 8.7 μg/L and 4.2 μg/L, respectively, which met the drinking water standard; In the co-adsorption system, As(V) and Cd(II) influence each other's adsorption behavior due to the anionic bridge and shielding effect of As(V) on Cd(II), As(V) gradually changed from monolayer adsorption to multi-layer adsorption dominant, while Cd(II) gradually changed from multi-layer adsorption to monolayer adsorption dominant. In this paper, the structure-activity relationship between material structure and synchronous removal of arsenic and cadmium was clarified, and the mechanism of synchronous removal was revealed, which provided technical guidance for synchronous removal of As(V) and Cd(II) from non-ferrous metal smelting wastewater. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: The alginate extraction residue from Brazilian Sargassum filipendula was employed as biosorbent for Zn(II) removal through a fixed‐bed column in order to explore its adsorptive properties and to establish a new use for this waste. RESULTS: The best operating conditions were 0.5 mL min‐1 and 1.0 mmol L‐1 (inlet concentration), providing lower mass transfer zone and higher uptake. Elution percentages of 52 and 73% were obtained for the first and second desorption cycles, respectively, using CaCl2 as eluent. The Yan et al. model was more representative of the experimental data. Characterization revealed that ion exchange is involved between zinc ions and light metals (Ca, Na, K and Mg). A decrease was observed in real and apparent densities of biomass, with an increase in particle porosity of the residue after process. CONCLUSION: The study revealed that this biomass has potential for Zn removal from aqueous solution, encouraging its application as a biosorbent in future studies involving multicomponent systems. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Heavy metal (HM) pollution of soil has become a gigantic issue across the globe. Metals enter the food chain and cause problems in plants, animals, and humans. We performed this work to evaluate the impacts of different cadmium (Cd) levels on growth, physiology, mineral nutrition, and yield attributes of Vigna radiata. Changes in growth fund are statistically significant and directly linked with an increase in Cd doses. Various concentrations of cadmium exhibited significant (p = 0.05) vicissitudes in biochemical parameters such as in the contents of chlorophyll, amino acids, soluble proteins, and total soluble sugars in experimental plants. The shoot and root calcium contents were highly reduced by higher concentrations of Cd in the following trend Cd40 > Cd30 > Cd20 > Cd10 than the control. Likewise, shoot and root potassium (K+) contents were less influenced by Cd10 as compared to other levels of Cd. The elevation in these enzymatic contents was maximum under the higher concentration of Cd (Cd40), and with the decreasing Cd level, a decline in concentrations of these estimated antioxidants was recorded (Cd30 > Cd20 > Cd10 > Cd0). A significant (p = 0.05) reduction in seed yield per plant and thousand seed weight was estimated with the increase in the concentration of Cd as compared to the control. The seed yield and their weights were less influenced in Cd10 treated plants followed by Cd20 and then Cd30. On the basis of the reported findings, our recommendation is to conduct research with an explicit focus on the mechanistic elucidation of damages caused by Cd. Additionally, target enzymes or metabolites in plants should be explored for use in the development of HM-tolerant crop varieties. [ABSTRACT FROM AUTHOR]

Heavy metal pollution has been regarded as a significant public health hazard during the industrialization, which also have exhibited various types of toxicological manifestations. Moreover, due to the high cost and toxic by-products, some conventional remediation methods were limited to heavy metals pollution control. In this work, autoclaved Saccharomyces cerevisiae was used as a biosorbent for the removal of Cd2+ and Pb2+ from single and binary ions aqueous solution system. The kinetics and isotherm of Cd2+ and Pb2+ were studied in different ion systems. The results showed that the competitive adsorption ability of S. cerevisiae to Pb2+ was stronger than that to Cd2+ in binary ions solution. To all the single ion solution of Cd2+ or Pb2+ and binary ions solution of Cd2+–Pb2+, there always existed that the adsorption of metal ions on S. cerevisiae fitted well with pseudo-second-order kinetic model and Langmuir isotherms model. The adsorption quantity qt in different solutions followed the sequence as qt (Cd2+–Pb2+) > qt (Pb2+-single) > qt (Pb2+-binary) > qt (Cd2+-single) > qt (Cd2+-binary). The autoclaved S. cerevisiae used in this research was one kind of rapid and favourable biosorbent for Pb2+ and Cd2+. In Pb2+ and Cd2+-containing solutions, sites competition and jointed toxicity of Pb2+ and Cd2+ on S. cerevisiae cells were the key to the total adsorption effect, and further researches were necessary in the next work. Thus, the current research presented that the autoclaved S. cerevisiae could be applied as an effective biosorbent for heavy metal adsorption from water environment and the design of eco-friendly technologies for the treatment of waste liquor. [ABSTRACT FROM AUTHOR]

The remediation of soil contaminated by heavy metals has long been a concern of academics. This is due to the fact that heavy metals discharged into the environment as a result of natural and anthropogenic activities may have detrimental consequences for human health, the ecological environment, the economy, and society. Metal stabilization has received considerable attention and has shown to be a promising soil remediation option among the several techniques for the remediation of heavy metal-contaminated soils. This review discusses various stabilizing materials, including inorganic materials like clay minerals, phosphorus-containing materials, calcium silicon materials, metals, and metal oxides, as well as organic materials like manure, municipal solid waste, and biochar, for the remediation of heavy metal-contaminated soils. Through diverse remediation processes such as adsorption, complexation, precipitation, and redox reactions, these additives efficiently limit the biological effectiveness of heavy metals in soils. It should also be emphasized that the effectiveness of metal stabilization is influenced by soil pH, organic matter content, amendment type and dosage, heavy metal species and contamination level, and plant variety. Furthermore, a comprehensive overview of the methods for evaluating the effectiveness of heavy metal stabilization based on soil physicochemical properties, heavy metal morphology, and bioactivity has also been provided. At the same time, it is critical to assess the stability and timeliness of the heavy metals' long-term remedial effect. Finally, the priority should be on developing novel, efficient, environmentally friendly, and economically feasible stabilizing agents, as well as establishing a systematic assessment method and criteria for analyzing their long-term effects. [ABSTRACT FROM AUTHOR]

Pollution and contamination of water with heavy metals is a global challenge which demands efficient, economic and sustainable solution. The grafting/addition of poly-functional groups (ligands) on the polysaccharides chains can high adsorption affinities towards heavy metals. Aerogels are a class of three-dimensional porous materials with outstanding physic-chemical characteristics (low density, high surface to volume ratio and controllable surface chemistry). In the recent years, aerogels have gained sufficient attention for the remediation of heavy metal ions from wastewater. The present review critically analyses the various synthesis routes for the cellulose aerogels and their applications as an adsorbent for heavy metal ions from water. This review critically analyzes the various synthesis routes for three-dimensional cellulose-based aerogels, their physico-chemical characterizations and removal mechanisms for the adsorption of heavy metal ions from water with insights into isotherm and kinetic models. Challenges (reactor configuration, scale-up, and proper selection of drying technique) and future research directions for the development of robust and efficient cellulose aerogels for the mitigation of heavy metal ions from water have also been elucidated. [ABSTRACT FROM AUTHOR]

Water care is an imperative duty in industries with effluents loaded with pollutants such as heavy metals, especially chromium (VI), extremely dangerous for humans and the environment. One way of treating water is possible through a continuous system with dry and crushed vegetable biomass of cellulose xanthogenate because it can adsorb heavy metals, especially due to its low production costs. Through continuous systems and with the waste of PET plastics, it is possible to develop a water treatment process adapting this system and biomass. The objective of this research is the development of a treatment for water contaminated with Cr (VI) using cellulose xanthogenate from E. crassipes on a pilot scale. Where a mass balance conducted to determine the adsorption capacity of this heavy metal, corroborating it through the Thomas model. The treatment process eliminated around 95% of Cr (VI) present in the water, in addition, biomass reuse cycles carried out, which maintained a considerable adsorption capacity in all the cycles conducted through EDTA reagent. [ABSTRACT FROM AUTHOR]

This research is focused on the preparation of macroporous poly(vinyl alcohol) (PVA)/chitosan (CS)/Al2O3 adsorbents for removal of residual metal ions from wastewater. The PVA/CS/Al2O3 adsorbents were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and energy dispersive X-ray (EDX) techniques to confirm that all compositions were incorporated into the PVA/CS/Al2O3 adsorbents without chemical modification. Furthermore, a comparison of the properties of the PVA/CS/Al2O3 adsorbents suggested that PVA/CS/0.50Al2O3 was the most suitable sample for adsorption study. The adsorption properties of PVA/CS/0.50Al2O3 for the removal of metal ions such as Pb2+, Cu2+, Zn2+, and Ni2+ in aqueous solution adsorbents in both single and quaternary systems were investigated. The results show that the adsorption selectivity of the PVA/CS/0.50Al2O3 adsorbent for these metal ions was provided in the following order: Pb2+ > Cu2+ > Zn2+ > Ni2+. The adsorption isotherm was studied by equilibrium data obtained from batch experiments. It was found that the Freundlich isotherm model was suitable for explaining the adsorption process. Adsorption kinetics were studied, which indicated that the adsorption of Pb2+, Cu2+, and Zn2+ followed a pseudo-second-order kinetic model, while the adsorption of Ni2+ followed a pseudo-first-order kinetic model. In addition, adsorption–desorption cycles were studied to prove the reusability of PVA/CS/0.50Al2O3 adsorbents. The PVA/CS/0.50Al2O3 adsorbents were able to be regenerated and reused. In a continuous adsorption process, a column experiment was simulated in laboratory. The results showed that Cu2+ was the most selective for a fixed-bed column. Thus, PVA/CS/0.50Al2O3 adsorbents could be potential used for toxic metal ion removal from wastewater, in both batch and fixed-bed continuous-flow columns. [ABSTRACT FROM AUTHOR]

Spent automobile batteries are one of the most significant secondary sources of harmful heavy metals for the environment. After being incorporated into the aquatic ecosystems, these metals disseminate to various plants, microorganisms, and the human body and cause multiple adverse effects. Activated carbons (ACs) have long been used as an effective adsorbent for different heavy metals in wastewater treatment processes. Although numerous research works have been published to date on this topic, they are scattered in the literature. In this review, we have assembled these works and provided an extensive overview of the application of ACs for treating spent car battery heavy metals (CBHMs) from aquatic systems. The preparation of ACs from different precursor materials, their application in the adsorption of CBHMs, the adsorption mechanism, kinetics, adsorption isotherms and various parameters that may affect the adsorption processes have been discussed in detail. A brief comparative analysis of the adsorption performances of ACs prepared from different precursor materials is also provided. Finally, recommendations for future research works are also offered. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is the biggest environmental problem of water related to the mining industry in many countries. Recently, coal mining and mineral mining industries use various AMD treatment systems. The main problem, however, is the very expensive and long retention times for treatment of AMD. For this reason, biosorption technology has been tested recently as a promising method for AMD treatment. The authors review presently available or potential biosorption methods to remove and detoxify toxic heavy metals and organic pollutants from AMD. Biosorption technology is evolving as an attractive option to supplement conventional AMD treatment. However, a literature review indicates that there is a lack of studies examining biosorption of AMD treatment. This paper examines a range of subjects, including laboratory scale experiments and the commercial application of biosorption for treatment of AMD. Our review paper will help direct future studies on the development of biosorption technology for treating AMD. [ABSTRACT FROM AUTHOR]

Biosorption is a better method compared to bioaccumulation for the removal of metal contaminants from aqueous solution. Out of different microbial species, fungi have more ability to remove and degrade heavy metal ions due to the presence of different negatively charged species and metal binder polysaccharide groups on its surface. Out of all the fungal species, Penicillium sp. is the mostly prominent one because of its large production and filamentous nature. But, its use in the removal of heavy metal ions from real industrial waste water is limited. Therefore, in the present article heavy metal ions from copper and zinc industrial waste water have been tried to be removed using Penicillium sp. and sodium alginate-immobilized Penicillium sp. Penicillium sp. is more specific towards copper compared to nickel. It has been observed that immobilized Penicillium sp. has more metal removal capacity compared to Penicillium sp. Zinc removal capacity of immobilized Penicillium sp. is much more compared to Penicillium sp. Since highly concentrated metal ions are difficult to be removed in a single stage of operation, total number of stages required for the complete removal of heavy metal contents of two industrial effluents have also been evaluated. The same has been confirmed by performing simulated runs. [ABSTRACT FROM AUTHOR]

Background: Cellulose polymers with multidentate chelating functionalities that have high efficiency for toxic metal ions present in water were designed, synthesized, and analyzed. The synthesis was carried out by reacting microcrystalline cellulose extracted from the solid waste of the olive industry with tert-Butyl acetoacetate (Cell-AA), produced cellulose with β-ketoester functionality was then reacted with aniline and the amino acid glycine to produce Cell-β-AN and Cell-β-GL, respectively. Results: The adsorption efficiency of the three polymers toward Pb(II) and various toxic metal ions present in sewage was evaluated as a function of adsorbent dose, time, temperature, pH value, and initial ion concentration to determine optimum adsorption conditions. The three polymers showed excellent efficiency toward about 20 metal ions present in a sewage sample collected from the sewer. The adsorption process follows the Langmuir adsorption isotherm model with a second-order of adsorption rate, the calculated qe values (2.675, 15.252, 20.856 mg/g) were close to the experimental qe values (2.133, 13.91, 18.786 mg/g) for the three polymers Cell-AA, Cell-β-AG and Cell-β-AN, respectively. Molecular Dynamic (MD) and Monte Carlo (MC) simulations were performed on the three polymers complexed with Pb(II). Conclusion: The waste material of the olive industry was used as a precursor for making the target cellulose polymers with β-Amino Ester Pendant Group. The polymer was characterized by SEM, proton NMR, TGA, and FT-IR spectroscopy. The efficacy of adsorption was quantitative for metal ions present in a real sample of wastewater and the efficiency didn't drop even after 7 cycles of use. The results indicate the existence of strong complexation. The thermodynamic study results showed a spontaneous bonding between of Pb(II) and the polymers pendant groups expressed by the negative value of the Gibbs free energy. [ABSTRACT FROM AUTHOR]

Ulcerative colitis (UC) imposes high economic burden to the health systems. However, the risk factors for development of the disease are still remained unknown. Exposure to heavy metals may be associated with occurrence of UC. The aim of this study was to evaluate the relationship between the concentration of metal(loid)s including Pb, As, Ni, Cu, Zn, Fe, and Se in drinking water with incidence of UC. To do this, 35 biopsy samples were each taken from patients and healthy subjects along with the same number of samples of their drinking water. The furnace atomic absorption spectrophotometry was used for sample analysis. Our results showed that exposure to Pb, As, Cu, and Fe was associated with occurrence of UC (ORs > 1; P < 0.05); meanwhile, the concentrations of Zn and Ni were higher in healthy subject biopsies than UC patients (ORs < 1; P < 0.05). Also, the mean concentration of Pb in the drinking water samples (0.12 ± 0.07 mg/L) was higher than the permissible limit of the Institute of Standards and Industrial Research of Iran (ISIRI). The results showed that by increasing Pb in drinking water, Zn concentration in the intestinal tissues of patients was decreased (P = 0.005). However, the concentration of Pb, As, Cu, and Fe in UC patients may affect the exacerbation of the disease, though Zn may potentially reduce the risk of this disease. In conclusion, our findings demonstrated that exposure to the metal ions through drinking water can affect the body's heavy metal content, which may be act as preventing or developing factors for UC. [ABSTRACT FROM AUTHOR]

Ethylenediaminetetraacetic acid (EDTA) washing has been used extensively to remediate heavy metal-contaminated soils. Electrochemical reduction treatment of spent washing solution is an effective method of EDTA regeneration. However, at present, these two technologies are usually regarded as two independent treatment processes. This research raised a new heavy metal-contaminated soil treatment strategy—a combination technique of coupled EDTA washing and electrochemical reduction. We speculated that the combination of EDTA washing and electroreduction treatment could improve the efficiency of Cd and Pb removal from contaminated soil. In this study, the removal performance and mechanisms of Cd and Pb under different current conditions were investigated based on a coupling of EDTA washing and electrochemical reduction. The combination technique can increase Cd and Pb removal efficiencies by 13.37–15.24% and 14.91–27.05%, respectively, compared with EDTA washing alone. Sequential extraction analysis showed that the reducible fraction improved metal removal efficiency. The percentage of metal removed increased with an increased current value and EDTA concentration. In addition, pulse current mode removed more Cd and Pb than continuous current, although the difference was not significant (p > 0.05). However, pulse current could effectively eliminate the cathodic hydrogen evolution reaction, resulting in a further heavy metal deposition at the cathode. The combination technique exhibited enhanced removal efficiency due to EDTA regeneration in the suspension and the cathodic reduction reaction. The most cost-effective treatment in 48 h was a pulse current mode of 32 min on/16 min off-32 mA-EDTA-10 mM, where 47.56% of Cd and 77.00% of Pb were removed from the soil with an electric energy consumption of 8.24 Wh. [ABSTRACT FROM AUTHOR]

Water contamination is an environmental burden for the next generations, calling for advanced methods such as adsorption to remove pollutants. For instance, unwanted biowaste and invasive plants can be converted into biosorbents for environmental remediation. This would partly solve the negative effects of invasive plants, estimated at 120 billion dollars in the USA. Here we review the distribution, impact, and use of invasive plants for water treatment, with emphasis on the preparation of biosorbents and removal of pollutants such as cadmium, lead, copper, zinc, nickel, mercury, chromate, synthetic dyes, and fossil fuels. Those biosorbents can remove 90–99% heavy metals from aqueous solutions. High adsorption capacities of 476.190 mg/g for synthetic dyes and 211 g/g for diesel oils have been observed. We also discuss the regeneration of these biosorbents. [ABSTRACT FROM AUTHOR]

Natural polymers such as chitosan, chitin, cellulose, alginate, pectin, and lignin produced by renewable organic resources are regarded as greener, sustainable, and eco-friendly materials. On account of their superior structural characteristics, abundant availability, nontoxicity, and ease of modification these naturel polymers are being used in the removal of dyes and heavy metal ions which can be carcinogenic, mutagenic, allergenic and toxic. However, to remove these contaminants, there are still challenges as pure natural polymers suffer from low surface area, low recovery and more solubility in water. Chemical modifications that lead to natural polymer composite formations have attracted much interest since the feauters they posses such as higher surface areas, porosities, reactivities as well as less solubility in water. In other words, natural polymer composites have better adsorption capacities towards dyes and heavy metal ions compared to the pure natural polymers. This review summarizes the appropriate literatures corresponding to the studies which include the applications of natural polymer composites for the removal of dyes and heavy metal ions in the last few years. A series of low cost natural polymer composites have been reviewed for their adsorption performance, adsorption mechanism, reusable feature, and the experimental conditions such as solution pH, contact time, dose amount, temperature. The NH2, COO−, OH, and NHCOOCH3 groups on polysaccharide composites behaved as effective sites for dyes and heavy metal capture. [ABSTRACT FROM AUTHOR]

Heavy metals released by various industries are among the major pollutants found in water resources. In this research, biosorption technique was employed to remove cadmium (Cd2+) from an aqueous system using a novel biosorbent developed from okara waste (OW), a residue from soya bean–based food and beverage processing. Characterisation results revealed that the OW biosorbent contained functional groups such as hydroxyl-, carboxyl- and sulphur-based functional groups, and the surface of the biosorbent was rough with multiple fissures which might be the binding sites for the pollutant. The effects of dosage, solution pH, initial Cd2+ concentration, temperature and contact time were investigated using batch adsorption mode. The biosorption equilibrium and kinetic were best described by the Langmuir and Elovich models, respectively. The maximum biosorption capacities predicted by the Langmuir model were 10.91–14.80 mg/g at 30–70 °C, and the biosorption process was favourable as evident from 0 < RL < 1. The uptake of Cd2+ by the OW biosorbent was spontaneous and endothermic. The plausible biosorption mechanisms of this study could be ionic exchange, hydrogen bonding and electrostatic interactions. The Cd2+ loaded OW biosorbent could be regenerated using 0.4 M of HCl solution and regeneration was studied for 4 adsorption-desorption cycles. The present investigation supported that OW can be reused as a value-added biosorbent product for the removal of Cd2+ from the contaminated water. [ABSTRACT FROM AUTHOR]

Seafood has long been considered a unique source of nutrition. However, increasing trends in consumption of marine products must be considered, especially in potentially polluted environments such as the Persian Gulf. This study was undertaken to analyse the level of heavy metal contamination of nickel (Ni), zinc (Zn), and lead (Pb) in shrimp (Penaeus merguiensis) captured from the northern Persian Gulf. The concentration of heavy metals in the muscle of shrimp followed the order Zn > Ni > Pb. The content of Zn and Ni was higher than recommended standard limits by the FAO/WHO. The combined impact of all metals was lower than the acceptable limit of 1 in shrimp. The carcinogenic risk for Ni was higher than the unacceptable value. In total, our finding indicated no potential health risk from the daily consumption of this species. However, long-term consumption of shrimp can pose a risk of carcinogenic effects of nickel. Continuous monitoring of these trace metals in seafood is necessary to ensure the quality of seafood and food safety. [ABSTRACT FROM AUTHOR]

In this study, a solid phase extraction method was successfully applied in the preconcentration and determination of trace levels of Cu(II) and Cd(II) ions and Phanerochaete chrysosporium (white rot fungus) modified bentonite was used as adsorbent. After the biosorption of Cu(II) and Cd(II) ions, metal concentrations in the samples were determined by atomic absorption spectrophotometry. pH, adsorbent amount, eluent type, sample volume, and flow rate, which are effective in the adsorption of metal ions, have been studied. 1 M HCl was used for desorption of these metal ions retained (recovery 95–100%). In addition, the effect of interfered ions has also been investigated. Sorption data were examined according to Langmuir and Freundlich adsorption equations. The results obtained show that the applied method has a high metal biosorption capacity, and Cu(II) and Cd(II) ions are successfully recovered. It was also successful in applying the proposed enrichment method to real water samples. Recovery values between 92.3% and 97.3% were obtained for the studied metal ions. According to the results, the proposed method can be successfully applied to water analysis at 95% confidence interval. [ABSTRACT FROM AUTHOR]

Biosorption is a technique widely used in the remediation of contaminated effluents, and its main advantages are its easy applicability, high efficiency rate, versatility, and its economic viability. Associated with nanotechnology, this work proposes the use of nanocomposites of sugarcane bagasse (SB) and ferromagnetic nanoparticles (Fe3O4) in the removal of metallic ions present in contaminated water. SB is a promising adsorbent material since it is an abundant agricultural residue, easily accessed. By using the coprecipitation method, two nanocomposites were obtained from in natura (SB-NP) or acid-treated (MSB-NP) sugarcane bagasse. These materials were synthetized by impregnation of Fe3O4 to gain paramagnetic properties and to facilitate the removal of the contaminant-containing adsorbent. The characterization of the nanocomposites was performed using pHPCZ, FTIR, XRD, and SEM/EDS techniques, to evaluate the synthesis efficiency and investigate the morphology of the materials. The efficiency of magnetite impregnation on the SB was assessed by SEM/EDS and XRD, while the main functional groups (carbonyl, carboxyl, hydroxyl, amine, amide, and nitrate) responsible for adsorption were found by FTIR. In the surface charge characterization by pHPCZ sorption of dyes, it was found that negative charges are predominant. The pHPCZ for SB-NP and MSB-NP was 5.95 and 5.59, respectively, and the chosen Cu(II) adsorption pH was 6.2 ± 0.1. The adsorption equilibrium was reached between 10 and 60 min of contact time. The maximum experimental sorption capacity (SCexp) was 2.53 ± 0.09 (SB-NP) and 2.61 ± 0.01 mg/g (MSB-NP). The isotherm models applied to the experimental data were Langmuir, Freundlich, Sips, Temkin, and Dubinin-Radushkevich, and Temkin best described the adsorption phenomena for Cu(II) by SB-NP (r2 = 0.9976 and χ2 = 3.965) and MSB-NP (r2 = 0.9990 and χ2 = 1.816). Reuse cycles of the nanocomposites were also performed employing ten cycles of sorption using 50 mg/L Cu(II) solutions, after which the materials showed SCexp = 7.47 ± 0.04 mg/g (SB-NP) and 7.82 ± 0.04 mg/g (MSB-NP). Therefore, the investigated materials exhibited promising results to be used as biosorbents in the remediation of effluents contaminated with toxic metal ions, such as copper. [ABSTRACT FROM AUTHOR]

Rising worldwide concern about the quantity and quality of water available to living beings calls for efficient technologies of water treatment. Nanomaterials are promising adsorbents to remove contamination from aqueous solution, and magnetic nanomaterials based on iron have attracted attention because magnetic materials are easy to separate. Here, we review iron magnetic nanomaterials applied for water and wastewater treatment, with focus on toxic elements, pharmaceuticals and pesticides. Major advances are: coprecipitation is the most used method for synthesis of iron magnetic nanoparticles, followed by solvothermal and hydrothermal methods. Magnetite is the most common magnetic nanoparticles applied as magnetic adsorbent. In general, magnetic nanocomposites are superparamagnetic, and the highest magnetization is sought for core–shell structures, reaching 65 emu/g. Most reports focus on removal of toxic metals. Adsorption is explained by the Langmuir isothermal model, kinetic patterns being correlated with pseudo-second-order equations. Overall, iron-based magnetic nanocomposites display promising performances for pollutant removal, yet few investigations report the toxic impacts of magnetic nanoparticles on the environment. [ABSTRACT FROM AUTHOR]

Treating biosolids from industrial, urban, and agricultural plants produces high amounts of water. After organic pollutants and non-essential heavy metals have been removed, these wastewaters are still rich in trace elements such as zinc (Zn), copper, or manganese (Mn) and have high conductivity and extremely variable pH. In this study, an isolated Chlorella sp. strain was grown for 21 days in nutrient solutions enriched with known amounts of Zn or Mn to obtain concentrations three (4.0 mg L−1)- and six (1.0 mg L−1)-fold higher than the basal medium levels, respectively, and over the limits permitted in aquatic environments. The green alga exhibited high tolerance to Zn and Mn, with the maximum abatement of Zn (28–30%) and Mn (60–63.5%) after 14 and 7 days of culture, respectively. Mn stimulated the growth rate and biomass production of Chlorella, which showed the highest carbon levels just in the first week. In both treatments, the nitrogen and protein contents remarkably increased. The photosynthetic pigments increased until the 14th day, with a higher extent in the Zn-enriched solution. An increasing photochemical efficiency was observed after 7 days of treatment, when the microalgae grown in Zn- and Mn-enriched solutions showed a slightly higher maximum photochemical efficiency than control. The autotrophic and controlled growth system adopted was designed to monitor the dynamic balance of Zn and Mn contents in the solutions and in the algal biomass. This system has proved to be useful in identifying the optimal nutritional conditions of the microalgae, along with the optimal temporal patterns of both metal biosorption capacity for water remediation and element bioaccumulation in the algal biomass. [ABSTRACT FROM AUTHOR]

Sargassum spp. are brown algae present in the tropical and subtropical waters of the world's oceans. Benthic or pelagic, Sargassum spp. represent substantial amounts of biomass when drifted and massive beaching events also named "golden tides" are challenging for environmental and tourism managers. The Sargassum spp. biomass can be regarded as offering economic opportunities; however, micropollutant contamination counteracts this wealth. This review describes the contaminant uptake processes and the concentrations reached by various Sargassum species in regard to national and international norms for a variety of applications. Amongst the heavy metals, perhaps total arsenic content is the most salient: phytoaccumulation of arsenic is due to confusion in the phosphate transporter between arsenic and phosphate, thus leading Sargassum spp. to bioaccumulate arsenic actively. The levels reached could well give cause for concern across all potential applications, in particular for human and animal use. Similarly, there are concerns for the widespread applications or disposal of this biomass due to environmental impacts in the case of storage, landfill or composting. Organic micropollutants are too rarely studied to assert that there is global contamination. However, research studies focused on Sargassum spp. contamination confirmed environmental threats. But, without exhaustive analysis of routine algae contamination, the standard contamination level cannot be defined. Treating beach-cast or drifting Sargassum spp. as a waste is a Gordian knot, in that it involves investment, work and disposal surfaces, whilst not necessarily providing environmental and economic gains. However, Sargassum spp. are a raw material, a resource rich in a broad variety of constituents that could be processed for commercial applications or which could be used for production of energy. In this paper the authors review the diverse applications that can be considered and describe the relevant regulations and norms related to contaminants and effluents that need to be taken into account. However, if valorizing Sargassum spp. is currently valuable and promising, the quality of the raw material is a key starting point because fresh and sand-free algae are required: offshore gathering solutions need to be developed in order to limit Sargassum sp. contamination by pollutants from land so as to hinder algae decay. [ABSTRACT FROM AUTHOR]

Heavy metals are environmental pollutants affect the integrity and distribution of living organisms in the ecosystem and also humans across the food chain. The study targeted the removal of copper (Cu2+) from aqueous solutions, depending on the biosorption process. The bacterial candidate was identified using 16S rRNA sequencing and phylogenetic analysis, in addition to morphological and cultural properties as Azotobacter nigricans NEWG-1. The Box-Behnken design was applied to optimize copper removal by Azotobacter nigricans NEWG-1 and to study possible interactive effects between incubation periods, pH and initial CuSO4 concentration. The data obtained showed that the maximum copper removal percentage of 80.56% was reached at run no. 12, under the conditions of 200 mg/L CuSO4, 4 days' incubation period, pH, 8.5. Whereas, the lowest Cu2+ removal (12.12%) was obtained at run no.1. Cells of Azotobacter nigricans NEWG-1 before and after copper biosorption were analyzed using FTIR, EDS and SEM. FTIR analysis indicates that several functional groups have participated in the biosorption of metal ions including hydroxyl, methylene, carbonyl, carboxylate groups. Moreover, the immobilized bacterial cells in sodium alginate-beads removed 82.35 ± 2.81% of copper from the aqueous solution, containing an initial concentration of 200 mg/L after 6 h. Azotobacter nigricans NEWG-1 proved to be an efficient biosorbent in the elimination of copper ions from environmental effluents, with advantages of feasibility, reliability and eco-friendly. [ABSTRACT FROM AUTHOR]

Contamination levels of copper (Cu) and other heavy metals are very high in the soils of the abandoned copper mine of Lasail in the north western Hajar Mountains of Oman. Environment-friendly approaches such as phytoremediation are needed to clean and rehabilitate these areas to their natural status. In the present study, the phytoremediation potential of castor, Ricinus communis L., was evaluated for copper and other heavy metals by growing it in different types of Cu-mine soils and slags. Growth parameters such as shoot height and biomass weight (fresh and dry) were evaluated. Castor showed a high tolerance index (TI) in Cu-mine soils. The highest TI was calculated for the fresh mass of castor shoots in E soil with a percentage of 405.99. The translocation factor (TF) of all the metals except boron (B) and manganese (Mn) was < 1, which reveals that these metals are stabilised in the root portion of the castor. Bioconcentration factor (BCF) value < 1 for Cu indicates that castor is not a hyperaccumulator plant for copper. In addition to high concentrations of copper, other heavy metals such as arsenic (As), iron (Fe), and zinc (Zn) were observed in the roots than in shoots. Castor grown in slag accumulated Cu in the shoots, roots, and entire plant with the values of 25, 1184, and 1209 mg kg−1, respectively. Similarly, castor cultivated in A soil accumulated 18, 901, and 919 mg kg−1 of copper in shoots, roots, and entire plant, respectively. The calculated plant effective number (PENt) indicated the need for 253 castor plants to remove 1 g of Cu from E soil. The ability of castor to grow well in Cu-mine soils suggests that it can be used for the removal of Cu and other heavy metals. Additionally, the shoot portion could potentially be used for oil production since the phytoaccumulation levels of heavy metal concentration in the shoots were below the standard toxicity limits. [ABSTRACT FROM AUTHOR]

The bioaccumulation capacity of water lettuce (Pistia stratiotes) including heavy metals has been well documented. However, its bioaccumulative efficiency for Pb, Cd, and Pb + Cd mixtures in nutrient-poor media is neglected. Therefore, the present study was aimed to investigate the bioaccumulative efficiency of the water lettuce by evaluating the bioconcentration factors (BCFs) and goodness-of-fit to regression models. Plants were exposed to various concentrations of Pb, Cd, and Pb + Cd mixtures in tap water for 1, 4, and 7 days. Heavy metal accumulation in whole plant tissue was measured with ICP-MS. The highest bioaccumulation rate was recorded at 1 day exposure tests for both metals as 14.9 mg/kg for Pb and 2.21 mg/kg for Cd. The BCFs for Pb and Cd ranged between 0.13 and 2.39 and 0.08 to 1.24, respectively. The modeling of the BCFs and exposure duration indicate that all of the models developed were significant. The R2 values were higher for single metal exposure tests. The model fitted curves demonstrate the decrease in BCFs with increasing exposure duration in all groups. Our results indicate that water lettuce can be used to treat nutrient-poor media polluted with low levels of Pb, Cd, and Pb + Cd mixtures for short incubation periods. [ABSTRACT FROM AUTHOR]

A lean method for calculation of the dynamic capacity of a sorbent as the time function has been suggested that employs a limited amount of experimental data for a sorption process of any duration and allows to obtain an analytical solution by quadrature. To its input parameters belongs a linear flow rate in an adsorber (column) rather than a volume flow rate. This simplifies a reproduction of the sorption process with the target kinetic characteristics at constructively different devices. The method applicability is independent of a kind of sorbent as well as of a number of sorbates in a multicomponent solution. The present paper represents both a theory of the method and its application to a particular case of the concurrent sorption of cations of three heavy metals, Cu(II), Ni(II) and Zn(II), on a natural multifunctional clay-like sorbent glauconite. [ABSTRACT FROM AUTHOR]

Sediment microbial fuel cell (SMFC) and constructed wetlands with macrophytes have been independently employed for the removal of heavy metals from polluted aquatic ecosystems. Nonetheless, the coupling of macrophytes at the cathode of SMFCs for efficient and synchronous heavy metal removal and bioelectricity generation from polluted river sediment has not been fully explored. Therefore, a novel macrophyte biocathode SMFC (mSMFC) was proposed, developed, and evaluated for heavy metals/organics removal as well as bioelectricity generation in an urban polluted river. With macrophyte-integrated cathode, higher heavy metal removals of Pb 99.58%, Cd 98.46%, Hg 95.78%, Cr 92.60%, As 89.18%, and Zn 82.28% from the sediments were exhibited after 120 days' operation. Total chemical oxygen demand, total suspended solids, and loss on ignition reached 73.27%, 44.42 ± 4.4%, and 5.87 ± 0.4%, respectively. A maximum voltage output of 0.353 V, power density of 74.16 mW/m3, columbic efficiency of 19.1%, normalized energy recovery of 0.028 kWh/m3, and net energy production of 0.015 kWh/m3 were observed in the Lemna minor L. SMFC. Heavy metal and organic removal pathways included electrochemical reduction, precipitation and recovery, bioaccumulation by macrophyte from the surface water, and bioelectrochemical reduction in the sediment. This study established that mSMFC proved as an efficient system for the remediation of heavy metals Pb, Cd, Hg, Cr, As, and Zn, and TCOD in polluted rivers along with bioelectricity generation. [ABSTRACT FROM AUTHOR]

The application of biosorption operation has gained attention in the removal and retrieval of toxic metal ions from water bodies. Wastewater from industrial activity generally presents great complexity due to the coadsorption of cations to the inactive biomass binding sites. In this work, the competitive biosorption of Cu(II) and Ag(I) ions was studied in batch systems. A kinetic study applying a non-acidified and acidified waste of Sargassum filipendula in equimolar and non-equimolar metal samples was carried out and the acidified biosorbent was selected due to higher removal rates and selectivity of silver ions. The assays were performed with 2 g L−1 of biosorbent concentration at 25 °C for 12 h and pH was controlled at around 5.0. Copper presented higher affinity for the biosorbent and a fast biosorption kinetic profile, while silver equilibrium times exhibited dependence on the copper concentration. External diffusion is the rate-limiting step in Cu(II) ion removal and it might also limit the kinetic rates of Ag(I) ions with intraparticle diffusion, depending on the initial concentration of metal cations. The ion-exchange mechanism is evidenced and complexation and electrostatic attraction mechanisms might be suggested, explained by simultaneous chemisorption and physisorption processes during the operation. Calcium and sodium were released in considerable amounts by the ion-exchange mechanism. Characterization analyses confirmed the role of several functional groups in the competitive biosorption accompanied by a homogenous covering of both metal ions on the surface of the particles. Particle porosity analyses revealed that the material is macroporous and an appreciable amount of macropores are filled with metal cations after biosorption. [ABSTRACT FROM AUTHOR]

Aided phytoremediation was studied for 48 weeks with the aim of reducing extractable and phytoavailable toxic elements and producing potential marketable biomass. In this sense, biomass of ryegrass was produced under greenhouse on two contaminated garden soils that have been amended with two successive additions of phosphates. After the first addition of phosphates, seeds of ryegrass were sown and shoots were harvested twice. A second seedling was performed after carefully mixing the roots from the first production (used as compost), soils and phosphates. Forty-eight weeks after starting the experiments, the concentrations of Cd, Pb, Zn, Cu, Fe, and Mn extracted using the rhizosphere-based method were generally lower than those measured before the addition of phosphates and cultivation (except for Pb and Fe in the most contaminated soil). The concentrations of metals in the shoots of ryegrass from the second production were lower than those from the first (except for Al). The best results were obtained with phosphates and were the most relevant in the lowest contaminated soil, demonstrating that the available metal concentrations have to be taken into account in the management of contaminated soils. In view of the concentration of metals defined as carcinogens, mutagens, and reprotoxics (e.g., Cd, Pb) and those capable to be transformed into Lewis acids (e.g., Zn, Fe), the utilization of ryegrass in the revegetation of contaminated soils and in risk management may be a new production of marketable biomass. The development of phytomanagement in combination with this type of biomass coincided with the view that contaminated soils can still represent a valuable resource that should be used sustainably. [ABSTRACT FROM AUTHOR]

Pillared interlayered clays have interesting properties such as high surface area, pore volume and extended pore size, high thermal stability, strong surface acidity and catalytic active substrates/metal oxide pillars. This article discusses the role of pillared clay as an adsorbent in various environmental and industrial applications. We present recent applications of clay-based porous nanomaterials in mitigation of pollutants such as heavy metals, vapours and gases, even at trace levels. Due to their unique characteristics, pillared clays are attractive candidates for catalytic decomposition, oxidation and adsorption of pollutants from gaseous and aqueous phases. This review explores the potential of different types of pillared clays as an adsorbent for various environmental applications. [ABSTRACT FROM AUTHOR]

Constructed wetland microcosms (CWMs) are artificially designed ecosystem which utilizes both complex and ordinary interactions between supporting media, macrophytes, and microorganisms to treat almost all types of wastewater. CWMs are considered as green and sustainable techniques which require lower energy input, less operational and maintenance cost and provide critical ecological benefits such as wildlife habitat, aquaculture, groundwater recharge, flood control, recreational uses, and add aesthetic value. They are good alternatives to conventional treatment systems particularly for smaller communities as well as distant and decentralized locations. The pH, dissolved oxygen (DO), and temperature are the key controlling factors while several other parameters such as hydraulic loading rates (HLR), hydraulic retention time (HRT), diversity of macrophytes, supporting media, and water depth are critical to achieving better performance. From the literature survey, it is evaluated that the removal performance of CWMs can be improved significantly through recirculation of effluent and artificial aeration (intermittent). This review paper presents an assessment of CWMs as a sustainable option for treatment of wastewater nutrients, organics, and heavy metals from domestic wastewater. Initially, a concise note on the CWMs and their components are presented, followed by a description of treatment mechanisms, major constituents involved in the treatment process, and overall efficiency. Finally, the effects of ecological factors and challenges for their long-term operations are highlighted. [ABSTRACT FROM AUTHOR]

Drinking water treatment plants produce significant amounts of waste sludge. In this study, removal of Nickel ion by use of wastewater sludge was aimed. The adsorption capability of waste sludge was optimized with varying physical parameters such as pH, adsorbent dosage, adsorbate concentration, contact time, shaking speed and temperature. Initial concentration was set as 25 mg/dm3, absorbent dose was set as 0.3 g/cm3, and temperature was set as 25 °C. Compliance of balance data with Langmuir, Freundlich, Temkin and D-R isotherm models was investigated. The highest R2 values were obtained with Freundlich isotherm (R2 = 0.92-0.95). Adsorption kinetics was analysed using pseudo-first order, pseudo-second order, Weber and Morris intraparticle diffusion and Elovich kinetic models, and the system was found to be in a better compliance with pseudo-second order kinetic model. Iron sludge was used as sorbent, and accordingly total iron ion measurements were carried out to determine its possible effects on water. Additionally, SEM, EDX, FTIR spectroscopy, XRD spectrum and atomic force microscope (AFM) measurements were conducted to determine the interaction between the sorbent and metal ions, in addition to characterization of the sorbent. As indicated by research results, drinking water treatment sludge proved to be a potential adsorbent for removal of nickel(II) ions from the solution. [ABSTRACT FROM AUTHOR]

High levels of heavy metals like copper ions in many industrial based effluents lead to serious environmental and health problems. Biosorption is a potential environmental biotechnology approach for biotreatment of aquatic sites polluted with heavy metal ions. Seaweeds have received great attention for their high bioremediation potential in recent years. However, the co-application of marine macroalgae for removal of heavy metals from wastewater is very limited. Thus, for the first time in literature, a coastal seaweed community composed of Chaetomorpha sp., Polysiphonia sp., Ulva sp. and Cystoseira sp. species was applied to remove copper ions from synthetic aqueous medium in this study. The biosorption experiments in batch mode were conducted to examine the effects of operating variables including pH, biosorbent amount, metal ion concentration and contact time on the biosorption process. The biosorption behavior of biosorbent was described by various equilibrium, kinetic and thermodynamic models. The biosorption of copper ions was strongly influenced by the operating parameters. The results indicated that the equilibrium data of biosorption were best modeled by Sips isotherm model. The values of mean free energy of biosorption computed from Dubinin-Radushkevich isotherm model and the standard Gibbs free energy change indicated a feasible, spontaneous and physical biotreatment system. The pseudo-second-order rate equation successfully defined the kinetic behavior of copper biosorption. The pore diffusion also played role in the control of biosorption process. The maximum copper uptake capacity of biosorbent was found to be greater than those of many other biosorbents. The obtained results revealed that this novel biosorbent could be a promising material for copper ion bioremediation implementations. [ABSTRACT FROM AUTHOR]

Liners are commonly used in engineered waste disposal landfill to minimize the potential contamination of the aquatic environment. The adsorption behavior of Cu(II) from aqueous solution onto clay admixed with various mix ratios of quarry fines was investigated. The amount of Cu(II) adsorption increases with increase in contact time. The copper removal efficiencies of the composite mixture gradually decrease from 94.53 % (raw clay) to 85.59 % (20 % of quarry fines with clay), and appreciable decrease in percent removal 75.61 % was found with 25 % of quarry fines with clay. The kinetic adsorption data were analyzed by pseudo-first-order, pseudo-second-order, Bhattacharya-Venkobachar and Natarajan-Khalaf kinetic models to classify adsorption process mechanisms. Kinetic experimental data were good agreement with pseudo-second-order kinetic model with the degree of fitness of the data ( R) 0.9999 for the adsorption of Cu(II). The results revealed that quarry fines can be used with optimum of 20 % replacement of natural clay for removal of Cu(II) as a liner material in landfills. [ABSTRACT FROM AUTHOR]

In the present study, removal of Cd, Cu, Ni and Pb from mono- and multi-metal ion aqueous solutions using natural Ca-bentonite was studied. Removal efficiency from synthetic aqueous solutions and real wastewater was investigated under various conditions such as variable concentration of metal ion, amount of clay, pH, and contact time. Increasing pH favors the removal of metal ions while the removal is rapid with maximum adsorption being observed within 20 min. Langmuir isotherm fits the data better in both single and multi-component systems. The monolayer adsorption capacities ( $$q_{m,i}^{o}$$ ) of bentonite for Cd, Cu, Ni and Pb in single metal systems were found as 31.25, 32.26, 26.32 and 85.47 mg g, respectively. The competitive adsorption equilibrium on a multi-component system (Cd/Cu/Ni/Pb) with different initial metal ion concentrations was also determined. For all studied metal ions, the adsorption capacities in the case of multi-component system ( $$q_{m,i}^{\text{mix}}$$ ) are lower than those obtained for the particular single metal system ( $$q_{m,i}^{o}$$ ). It was observed that the equilibrium uptake amounts of each metal Cd, Cu, Ni and Pb in the multi-component system onto bentonite decreased considerably with increasing concentrations of the other metals due to their antagonistic effect. Bentonite displays a high selectivity toward one metal in a multi-component system with an affinity order of Cu > Ni > Pb > Cd which is related to the first hydrolysis equilibrium constant. The values of $${{q_{m,i}^{\text{mix}} } \mathord{\left/ {\vphantom {{q_{m,i}^{\text{mix}} } {q_{m,i}^{o} < 1}}} \right. \kern-0pt} {q_{m,i}^{o} < 1}}$$ demonstrate the mutual competitive effect between heavy metals in multi-component systems. [ABSTRACT FROM AUTHOR]

Heavy metals contamination in water has been an issue to the environment and human health. The persisting contamination level has been observed and concerned by the public due to continuous deterioration of water quality. On the other hand, conventional treatment system could not completely remove the toxic metals in the water, thus alternative purification methods using inexpensive materials were endeavor to improve the current treatment process. Wide ranges of low cost adsorbents were used to remove heavy metal in aqueous solution and wastewater. The low cost adsorbents were usually collected from agricultural waste, seafood waste, food waste, industrial by-product and soil. These adsorbents are readily available in a copious amount. Besides, the pretreatment are not complicated to be conducted on the raw products, which is economically sound for an alternative treatment. The previous studies have provided much evidence of low cost adsorbents' efficiency in removing metal ions from aqueous solution or wastewater. In this review, several low cost adsorbents in the recent literature have been studied. The maximum adsorption capacity, affecting factors such as pH, contact times, temperature, initial concentration and modified materials were revised and summarized in this review for further reference. Comparisons of the adsorbent between the modified and natural products were also demonstrated to provide a clear understanding on the kinetic uptake of the selected adsorbents. Some of the natural adsorbents appeared as good heavy metal removal, while some were not and require further modifications and improvements to enhance the adsorption capacity. SWOT analysis (strength, weakness, opportunities, threat) was also performed on the low cost adsorbents to identify the advantages of using low cost adsorbents and solve the weaknesses encountered by the utilization of low cost materials. This tool helps to determine the potential quality of low cost materials in the application for water and wastewater treatment. [ABSTRACT FROM AUTHOR]

In the present study, continuous up-flow fixed-bed column study was carried out using immobilized dead biomass of Aeromonas hydrophila for the removal of Cr(VI) from aqueous solution. Different polymeric matrices were used to immobilized biomass and polysulfone-immobilized biomass has shown to give maximum removal. The sorption capacity of immobilized biomass for the removal of Cr(VI) evaluating the breakthrough curves obtained at different flow rate and bed height. A maximum of 78.58% Cr(VI) removal was obtained at bed height of 19 cm and flow rate of 2 mL/min. Bed depth service time model provides a good description of experimental results with high correlation coefficient (>0.996). An attempt has been made to investigate the individual as well as cumulative effect of the process variables and to optimize the process conditions for the maximum removal of chromium from water by two-level two-factor full-factorial central composite design with the help of Minitab ® version 15 statistical software. The predicted results are having a good agreement ( R2 = 98.19%) with the result obtained. Sorption–desorption studies revealed that polysulfone-immobilized biomass could be reused up to 11 cycles and bed was completely exhausted after 28 cycles. [ABSTRACT FROM AUTHOR]

In this study, the scales of Micropogonias undulatus fish were investigated as precursors for the development of low-cost biosorbent for the removal of Pb(II) and Zn(II) from aqueous media. The biosorbent was characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffractometry (XRD). Adsorption parameters (temperature, biosorbent dosage and contact time) were optimised using response surface methodology Box–Behnken experimental design. The optimal factors for Zn(II) removal by croaker fish scale were 145.5 min, 7.01 g/L biosorbent dosage, 30 °C and pH 5.4. The optimal factors for the removal of Pb(II) were 179.3 min, 6.61 g/L biosorbent dosage, 20 °C and pH 3.4. The numerical optimisation revealed that the optimal removal efficiency for Zn(II) and Pb(II) sorption is 96.45% and 98.76%, respectively. The biosorption of both heavy metals was best fit to Freundlich isotherm and pseudo-second-order kinetic models. Thermodynamics studies revealed that the biosorption process was exothermic and spontaneous. [ABSTRACT FROM AUTHOR]

The adsorption behavior of β-zeolite prepared with different Si/Al ratio from synthesis gel and the effect of their chemical and textural properties on the zinc, copper and cadmium ions removal from aqueous solutions are studied in this work. The samples were characterized by N2 physisorption, X-ray diffraction, X-ray fluorescence, scanning electron microscopy and solid-state 27Al nuclear magnetic resonance spectroscopy. The chemical composition, structure, and textural properties of the β-zeolites were found to depend on the initial Al content in the synthesis gel. It was verified that the solid with higher content of framework aluminum also presented higher surface-to-volume ratio. This suggests that a higher initial Al content directly affects the nucleation kinetics of the β-structure, ensuring a solid with high density of accessible ion-exchange sites for metal uptake. Consequently, the amount of metal adsorbed onto β-zeolites was influenced by their textural and chemical properties. It was found that the monolayer capacity follows the order: Cd2+ (29.5 mg g−1) ≈ Cu2+ (29.5 mg g−1) > Zn2+ (17.3 mg g−1) and Cd2+ (23.1 mg g−1) > Cu2+ (14.1 mg g−1) > Zn2+ (11.1 mg g−1), for BETA 40 and BETA 60, respectively. The uptake selectivity order depends on the hydration energy, hydrated ion diameter and electronegativity of the metals. Kinetic studies followed the pseudo-second order model, while the adsorption isotherms were well described by the Langmuir model, suggesting that the adsorption process took place by ion exchange on the zeolite monolayer surface, since all values of mean free energy of adsorption are in the range 8–16 kJ mol−1. [ABSTRACT FROM AUTHOR]