Adsorbent For Removal Of Heavy Metals Research Articles

Evaluating the performance of cement-modified biochar adsorbent for Cu, Pb and Zn removal from urban stormwater

This research investigates the use of biochar modified with Ordinary Portland Cement (OPC) as an adsorbent for heavy metal removal and evaluates the impact of competing ions and nutrients on the adsorptive removal process. The cement-modified biochar composites, featuring functional groups from biochar and hydrated OPC, exhibited significantly enhanced adsorption capacities for Cu, Pb, and Zn, approximately 3.3, 2.4, and 6 times higher, respectively, compared to unmodified biochar upon introducing 1.5 % (v/v) OPC. The Langmuir monolayer adsorption model accurately described the adsorption data, with heavy metals binding to functional groups like CC and CO, CO3–2, silanols (Si-OH), siloxanes and calcium silicate hydrate. The cement-modified biochar composite exhibited notable adsorption capacities for Cu, Pb, and Zn at 28.82 mg/g, 38.76 mg/g and 26.53 mg/g, comparable to commercial activated carbons. There were negligible effects from NO3- on the removal of Cu, Pb and Zn, PO43- ions enhanced Pb removal, and NH4+ ions slightly reduced the removal of all three metals, while humic acid increased removal. The findings indicate that using OPC boosts heavy metal adsorption, and insights into the influence of competing ions and nutrients apprise strategies for using OPC-modified biochar in practical applications.

Facile Synthesis of Sodium Dodecyl Sulfate Intercalated Mg‐Al LDH and its Excellent Adsorption Performances for Cu2+ from Aqueous Solution

AbstractIn this study, the magnesium aluminum layered double hydroxide intercalated with sodium dodecyl sulfate (Mg‐Al S‐LDH) was synthesized by using a roasting–restoration method based on the Mg‐Al LDH precursor, and their effectiveness in removing Cu2+ from aqueous solutions was investigated. Detailed microstructural characterization of these adsorption materials involved employing X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms (N2 ad/desorption), and thermogravimetric‐differential thermal gravimetric analysis (TG‐DTG). The experimental results revealed that Mg‐Al S‐LDH displayed a plate‐like layered structure with a larger surface area and enhanced adsorption ability. Specifically, the maximum adsorption capacity, reaching 96.15 mg ⋅ g−1, was achieved at a temperature of 298 K, accompanied by a rapid adsorption rate. The adsorption kinetics adhered to the pseudo‐second‐order model, suggesting that chemisorption controlled the adsorption behavior. Furthermore, the adsorption of Cu2+ followed the Freundlich model, signifying a multi‐site adsorption mechanism onto the surface and layers of Mg‐Al S‐LDH. Thermodynamic investigations indicated that higher temperatures facilitated Cu2+ dissolution and strengthened the affinity with Mg‐Al S‐LDH, with a positive ΔHΘ value suggesting that the Cu2+ adsorption process was endothermic and temperature‐enhancing. Ion selectivity experiments demonstrated that Cd2+ and Pb2+ ions had a significant impact on Cu2+ adsorption, while the effects of Zn2+ and Fe2+ ions were less pronounced. The primary adsorption mechanisms of Cu2+ onto Mg‐Al S‐LDH encompassed precipitation, complexation on the surface and layers, and isomorphous substitution. This study sheds light on the promising potential of Mg‐Al S‐LDH as an effective adsorbent for heavy metal removal and provides valuable insights into its adsorption mechanisms and performance in different environmental conditions.

Investigation of adsorptive removal of heavy metals onto magnetic core–double shell nanoparticles: kinetic, isotherm, and thermodynamic study

The most perilous environmental hazards arise from the contamination of water by heavy metal ions, owing to the non-biodegradability of these metals, as well as their rapid dissemination throughout components of the environment via the food chain. Nano-based adsorbents have been used for the adsorption removal of many heavy metal cations, but separating and recycling them represent significant difficulties in processing. Magnetic core–double shell nanoparticles provide an attractive solution for processing issues, since they are stable and can be easily separated and recycled. Moreover, the shell thickness, composition, and porosity can be easily tuned. In this work, two samples consisting of magnetic core@TiO2@mesoSiO2 nanoparticles with two shell thicknesses (Mag-T-S-0.2 and Mag-T-S-0.4), along with a magnetic core@SiO2@TiO2 nanoparticle sample (Mag-S-T), were synthesized and characterized by TEM, XRD, magnetic strength measurement and zeta potential. TEM images show the developed core–double shell structure with double shell ranging from 60 to 73 nm. The XRD results indicate the impact of the outer shell on the diffraction pattern. The zeta potential shows that all samples had a negative charge at pH over 4. The magnetic character was suppressed after the formation of the double-shell coating; however, the magnetic core–double shell nanoparticles still had magnetization and could be separated when an external magnetic field was applied. The heavy metal adsorptive ability of Mag-T-S-0.2, Mag-T-S-0.4, and Mag-S-T samples was explored to investigate the effects of shell type and thickness along with kinetic, isotherm, and thermodynamic study. The investigated heavy metals included Cd(II), Ni(II), Mn(II), Pb(II), and Cu(II). The results indicate that, for Mag-T-S-0.2, the equilibrium state occurred after 15 min contact time, with adsorption capacity of 238, 230, 210.6, 181.8, and 245.8 mg/g for Cd(II), Ni(II), Mn(II), Pb(II), and Cu(II), respectively. For Mag-T-S-0.4, the equilibrium state occurred after 15 min contact time, with adsorption capacity of 241, 237.6, 173.8, 189.6, and 257.2 mg g−1, respectively. For Mag-S-T, the equilibrium state occurred after 25 min contact time, with adsorption capacity of 137.8, 131.4, 221, 189.6, and 149.4 mg g−1, respectively. When pseudo-first-order and pseudo-second-order kinetic models were applied to investigate the time interval adsorption data for Mag-T-S-0.2, Mag-T-S-0.4, and Mag-S-T samples, the second-order kinetic model was found to be more suitable for describing the process, indicating a fast adsorption mechanism. The adsorption data did not fit well with the Langmuir model, while they did fit well with the Freundlich model, suggesting heterogeneous material surfaces and multi-layer adsorption. Thermodynamic investigations confirmed the spontaneous nature of adsorptive removal, which helps to promote magnetic core@TiO2@mesoSiO2 and magnetic core@SiO2@TiO2 nanoparticles as effective adsorbents for wastewater treatment.

Cation Effect in Polysaccharide-Based Hydrogel Beads Produced for Europium Adsorption from Aqueous Solutions

AbstractIn recent decades, renewable and biodegradable polysaccharide-based hydrogels have enjoyed wide applicability among them also as adsorbents for heavy metal removal from wastewaters. Herein we prepared hydrogel beads from iota and kappa carrageenans using a variety of salts as crosslinkers, that were tested for the first time in europium ion (Eu3+) sorption from an aqueous solution as representative lanthanide. The type of the salt, and especially the valance and the hydrated radius of the cation, were found to dictate hydrogel bead formation and structure and, therefore, the Eu3+ sorption yield. The results of ATR-FTIR, SEM and TGA analyses to characterize the iota carrageenan hydrogel beads that were prepared with alkali cations, before and after interaction with Eu3+, indicate that the adsorbent prepared with LiCl was much stiffer and more stable than those prepared with NaCl or KCl. The iota carrageenan beads that were prepared with LiCl were also reused 5 times while exhibiting high adsorption capacities.

ADSORTION POTENTIAL OF GARLIC, GINGER AND LEMON IN THE REMOVAL OF HEAVY METALS FROM AQUEOUS SOLUTIONS

This work was conducted to assess the efficiency of Garlic, Ginger and Lemon in the removal of some Heavy Metals from aqueous solution. Batch adsorption process was employed in the experiments. Different dosages (0.2, 0.4, 0.6, 0.8 and 1.0) g of the adsorbents and concentrations of the heavy metals (1000ppm, 800ppm, 600ppm, 400ppm, and 200ppm) were prepared and used. Flame Atomic Absorption Spectroscopic (FAAS) was used to determine the amount of heavy metal concentrations adsorbed at each stage of the experiment. Results obtained show that there was remarkable reduction of metal concentrations in the solutions. However, comparatively, the efficiency of garlic in absorbing the metals is greater than that of ginger and lemon at all conditions. Thus, results obtained suggest that Garlic, Ginger and Lemon could be promising adsorbents for heavy metal removal in aqueous solutions, but garlic has greater efficiency in adsorbing the metals particularly zinc and copper.

Wastewater Treatment Utilizing Industrial Waste Fly Ash as a Low-Cost Adsorbent for Heavy Metal Removal: Literature Review

Wastewater discharges from industrial processes typically include elevated concentrations of contaminants, which largely consist of potentially harmful chemicals such as heavy metals. These contaminants are characterized by their slow rate of decomposition. Hence, the removal of these metallic ions from effluents poses a challenge. Among different treatments, the adsorption approach has considerable potential due to its ability to effectively eliminate both soluble and insoluble pollutants from effluent, even at lower levels of concentration. Of various wastes, fly ash (FA) material has been the subject of attention because it is abundant, has favorable qualities, and contains a high percentage of minerals. This review investigates multiple facets, with a specific focus on the application of FA, an industrial byproduct, as an adsorbent in removing heavy metals. A comprehensive examination was conducted on a range of concerns pertaining to the pollution caused by metallic ions, including the underlying causes, levels of contamination, health implications of heavy metals, and removal methods. Multiple factors were found to affect the adsorption process. Of all the factors, the pH value considerably influences the elimination of heavy metals. An acidic pH range of 2.5–4.5 was found to be optimal for achieving the highest possible elimination of As(V), Cu(II), Hg(II), and Cr(VI). The latter elimination rate reached 89% at the optimal pH level. Most heavy metals’ adsorption isotherms conformed to the Langmuir or Freundlich models, while the pseudo-second-order kinetics provided a satisfactory match for their removal. Using a raw FA, adsorption capacities were achieved in the removal of metallic ions, Ni(II), Pb(II), and Cr(VI), that ranged from 14.0 to 23.9 mg g−1. Meanwhile, the FA-zeolite showed a remarkable capacity to adsorb ions Mn(II), Ni(II), Cd(II), Cu(II), and Pb(II), with values ranging from about 31 to 66 mg g−1. The cost analysis showed that the treatment of FA is economically advantageous and may result in significant cost reductions in comparison to commercial adsorbents. In summary, FA is an inexpensive waste material with potential for water treatment applications and several other purposes due to its excellent chemical and mineralogical composition.

Synthesis of Nano-silica Oxide for Heavy Metal Decontamination from Aqueous Solutions

In the current study, nano-silica oxide (nano-SiO2) was fabricated via the sol-gel technique. Then, the prepared nano-SiO2 was characterized using X-ray diffractometer (XRD), transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) specific surface area analysis. Furthermore, the fabricated nano-SiO2 was applied for the adsorption of lead Pb (II) and chromium Cr (VI) from aqueous solutions. Additionally, the influence of different operating factors such as contact time (0–180 min), initial pH (1–11), nano-SiO2 dose (0.1–8 g L−1), initial metal ion concentration (5–100 mg L−1), and the temperature (30–85 °C) was investigated. The nano-SiO2 doses of 0.5 and 1 g L−1 were selected as the optimal adsorbent dose for the removal of Pb (II) and Cr (VI), respectively. These doses achieved a removal efficiency of 82.3% and 78.5% for Pb (II) and Cr (VI), after 60 and 90 min, at initial pH values of 5 and 2, respectively, using 10 mg L−1 initial metal concentration, and at room temperature. Lastly, kinetic and equilibrium studies were competently fitted using the pseudo-second-order and Freundlich models, respectively. Adsorption thermodynamic studies designate the spontaneous and thermodynamic nature of the adsorption process. These results reveal the efficiency of the fabricated nano-SiO2 as an adsorbent for heavy metal removal from aqueous solutions.Graphical

Adsorptive removal of heavy metals from wastewater using Cobalt-diphenylamine (Co-DPA) complex

Heavy metals like Cadmium, Lead, and Chromium are the pollutants emitted into the environment through industrial development. In this work, a new diphenylamine coordinated cobalt complex (Co-DPA) has been synthesized and tested for its efficiency in removing heavy metals from wastewater, and its adsorption capacity was investigated. The effectiveness of heavy metals removal by Co-DPA was evaluated by adjusting the adsorption parameters, such as adsorbent dose, pH, initial metals concentration, and adsorption period. Heavy metal concentrations in real sample were 0.267, 0.075, and 0.125 mg/L for Cd2+, Pb2+, and Cr3+ before using as-synthesized Co-DPA to treat wastewater. After being treated with synthesized Co-DPA the concentration of heavy metals was reduced to 0.0129, 0.00028, 0.00054 mg/L for Cd2+, Pb2+, and Cr3+, respectively, in 80 min. The removal efficiency was 95.6%, 99.5%, and 99.5% for the respective metals. The adsorption process fitted satisfactorily with Freundlich isotherm with R2(0.999, 0.997, 0.995) for Cd2+, Pb2+, and Cr3+, respectively. The kinetic data obeyed the pseudo-second order for Cd2+ and Cr2+ and the pseudo-first order for Pb2+. Based on the results obtained within the framework of this study, it is concluded that the as-synthesized Co-DPA is a good adsorbent to eliminate heavy metal ions like Cd2+, Pb2+, and Cr3+from wastewater solution. In general, Co-DPA is a promising new material for the removal of heavy metal ions from water.Graphical

Carboxylic acid functionalized para-xylene based hypercrosslinked polymer as a novel and high performance adsorbent for heavy metal removal

In this work, hypercrosslinked polymeric adsorbent (HCP) was synthesized from para-Xylene precursor through Friedel-Crafts reaction. Additionally, heavy metal adsorption experiments from a multi component system including lead, cadmium, nickel, and copper ions were conducted. To enhance lead uptake selectivity over other metallic ions, the resulting HCP sample was functionalized through carboxylic acid incorporation into the HCP adsorbent skeleton. The adsorption process modeling was carried out by using Central Composite Design- Response Surface Methodology technique. In addition, the adsorption capability dependency of the resulting samples to the operational condition including temperature from 25 °C to 65 °C, solution pH value from 4 to 10, and solution initial concentration from 20 mg/l to 100 mg/l was investigated. Additionally, process optimization was applied aim to maximize the lead uptake selectivity, the optimal condition including a temperature of 31.8 °C, pH of 5.0, and initial concentration of 82.50 mg/l were obtained for HCP sample, also the optimal condition namely a temperature of 30 °C, pH of 5.5, and initial concentration of 100 mg/l were obtained for modified HCP sample. As a result of isotherm modeling, the Hill model was obtained as the best model, additionally, thermodynamically investigation of the process resulted in spontaneously and physically adsorption of the metallic ions by HCP samples, with respect to Gibbs free energy (ΔG0 < 0) and adsorption process enthalpy (ΔH0 < 20 kJ/mol). Finally, adsorbents regeneration were evaluated and minor losses in the adsorption capacity of samples were yielded after ten cycles.

Resourcization of Argillaceous Limestone with Mn3O4 Modification for Efficient Adsorption of Lead, Copper, and Nickel.

Argillaceous limestone (AL) is comprised of carbonate minerals and clay minerals and is widely distributed throughout the Earth's crust. However, owing to its low surface area and poorly active sites, AL has been largely neglected. Herein, manganic manganous oxide (Mn3O4) was used to modify AL by an in-situ deposition strategy through manganese chloride and alkali stepwise treatment to improve the surface area of AL and enable its utilization as an efficient adsorbent for heavy metals removal. The surface area and cation exchange capacity (CEC) were enhanced from 3.49 to 24.5 m2/g and 5.87 to 31.5 cmoL(+)/kg with modification, respectively. The maximum adsorption capacities of lead (Pb2+), copper (Cu2+), and nickel (Ni2+) ions on Mn3O4-modified argillaceous limestone (Mn3O4-AL) in mono-metal systems were 148.73, 41.30, and 60.87 mg/g, respectively. In addition, the adsorption selectivity in multi-metal systems was Pb2+ > Cu2+ > Ni2+ in order. The adsorption process conforms to the pseudo-second-order model. In the multi-metal system, the adsorption reaches equilibrium at about 360 min. The adsorption mechanisms may involve ion exchange, precipitation, electrostatic interaction, and complexation by hydroxyl groups. These results demonstrate that Mn3O4 modification realized argillaceous limestone resourcization as an ideal adsorbent. Mn3O4-modified argillaceous limestone was promising for heavy metal-polluted water and soil treatment.

The utilization of date palm waste as an efficient adsorbent for the elimination of heavy metals from polluted water.

This study focuses on the removal of heavy metal ions, such as cadmium (Cd2+), lead (Pb2+), chromium (Cr6+), and zinc (Zn2+) from water. Metals, which are often present in water, can have various origins, i.e., industrial emissions, mining, melting, corrosion, municipal, industrial waste, and agrochemicals. These metals have the potential to cause adverse effects on human health. The study employed activated carbon derived from date palm waste as a means of removing heavy metals. The activated nanoparticles were characterized using various analytical techniques, including SEM, ICP, XRD, BET, Raman, and FTIR analysis. Batch studies were conducted to optimize the metal ion adsorption onto the activated carbon of date palm waste. The adsorption process was evaluated using isotherm models and reaction kinetics under various conditions, including contact time, dosage, pH, and initial concentration. The findings of this study revealed that the prepared activated carbon from date palm waste effectively removed up to 85% of Cr6+, Pb2+, Cd2+, and Zn2+ ions from water. This study highlights the potential of using agricultural waste, to produce effective adsorbents for heavy metal removal.

DOTA functionalized adsorbent DOTA@Sludge@Chitosan derived from recycled shrimp shells and sludge and its application for lead and chromium removal from water

DOTA@Sludge@Chitosan was synthesized by a facile treatment using DOTA (1,4,7,10-tetraazacyclododecane-N,N′,N,N′-tetraacetic acid) to modify dry sludge and chitosan in an acidic solution. The performance of developed DOTA@Sludge@Chitosan was investigated for the adsorptive removal of Cr6+ and Pb2+ from water. Characterization studies showed that the materials possess a large surface area (52.009 m2/g), pore volume (0.069 cm3/g), and abundant functional groups of amino and hydroxyl. The prepared material showed a synergetic effect due to carboxylic acid and sludge, effectively removing Cr6+ and Pb2+. It reached 329.4 mg/g (Pb2+) and 273.3 mg/g (Cr6+) at 20 °C, much higher than commercial activated carbon. The regeneration of the adsorbent was tested for six adsorption and desorption cycles. The results demonstrate that the DOTA@Sludge@Chitosan adsorbent well-maintained high adsorption capacity attributed to its stability, making it a promising adsorbent for heavy metals removal from industrial effluent.

Adsorptive removal of heavy metals, dyes, and pharmaceuticals: Carbon-based nanomaterials in focus

The use of carbon-based nanomaterials, including carbon nanotubes, carbon dots, graphene/graphene oxide, fullerene, and their derivatives, in the removal of emerging pollutants from wastewater has become a promising method in water treatment. These nanomaterials exhibit exceptional adsorption capabilities and selectivity due to their extensive surface area, customizable surface chemistry, and unique structural features, which involve factors like π-π interactions, electrostatic interactions, and specific surface functional groups. A notable experiment demonstrated the effectiveness of carbon nanotubes as adsorbents for removing Ismate violet 2R dye from contaminated water. The results showed a remarkable maximum removal efficiency of 91.71 % at a concentration of 10 mg/L within a brief 120-min period. This article conducts a comprehensive evaluation of the adsorptive removal of emerging pollutants from wastewater using carbon-based nanomaterials, with a focus on developments between 2015 and 2023. An in-depth bibliometric analysis of 1285 research publications retrieved from the Web of Science (WOS) and Scopus databases reveals a substantial increase in the number of publications, rising from 50 in 2015 to 158 in 2023. This signifies a burgeoning emphasis on both practical application and technological advancement in this domain. Furthermore, this review explores the intricacies of adsorption mechanisms, factors influencing the adsorption performance of carbon-based nanomaterials, and the associated challenges and limitations when applied in wastewater treatment. By thoroughly investigating these constraints and potential advantages, this article provides valuable insights for the development of future carbon-based nanomaterials, aiming to enhance their efficiency and expand their applications in the field of wastewater treatment.

The Effect of Chemical Treated Okra Waste for Heavy Metal Adsorption from Natural Gas Production Wastewater

Nowadays, one of the leading environmental pollutants is heavy metals. Hence, heavy metals in wastewater must be removed before discharge because they are toxic even at low concentrations. This research aims to evaluate the efficiency of okra waste as an adsorbent for heavy metals removal from wastewater in natural gas production. In this study, chemical activation of okra adsorbent was processed to increase the surface area of okra adsorbent for better adsorption, whenever the impregnation of the powdered okra waste was performed using phosphoric acid (H3PO4) as the impregnating agent. The okra powder was impregnated at a rate of 4: 1 (v / m). The FTIR was used to characterize the okra-activated carbon and the peaks showed the presence of functional groups such as Hydroxyl (OH), Amino (N-H), Carboxyl (C=O, C-O-C), C-0 stretching and M-O at 3390.05, 2905.5, 1640-1658, 1050.05 and 650 stretching bands respectively. Furthermore, the batch adsorption experiments were conducted via varying agitation speed, contact time, adsorbent dose and adsorbent particle sizes. The results showed that the maximum removal percent of Cd2+, Cu2+, Pb2­+, Zn 2+, Ag2+ and Ba2+metal ions had been observed to be at an agitation speed of 1000 rpm, contact time of 90 min­, okra adsorbent dose of 0.25 g and particle size of 1.00mm. The experimental findings show that okra wastes from agricultural by-products may be a low-cost adsorbent for future research to remove additional heavy metals owing to their high effectiveness in removing Cd2+, Cu2+, Pb2+, and Zn2+ ions from wastewater.

3D-Printed Filters for Efficient Heavy Metal Removal from Water Using PLA@CS/HAP Composites.

Chitosan/Hydroxyapatite composites, enriched with relatively active -NH2 and -OH groups, have emerged as promising adsorbents for heavy metal removal. In this study, we harnessed the potential of CS/HAP composites by developing monolithic PLA@CS/HAP filters utilizing 3D printing and freeze-drying techniques. These filters possess both macroscopic and microscopic porous structures, endowing them with exceptional capabilities for removing heavy metals from water. The adsorption properties of CS/HAP composites were explored by varying the dosage, duration, and initial concentrations of copper ions. The maximum adsorption capacity for Cu2+ was determined to be approximately 119+/-1 mg/g at the natural pH and 298 K. Notably, the monolithic PLA@CS/HAP filters demonstrated remarkable efficiency in the removal of copper ions, with 90% of copper ions effectively removed within a mere 2-h period in a cyclic adsorption experiment. Furthermore, the PLA@CS/HAP filters exhibited a robust dynamic Cu2+ removal capacity (80.8% or even better in less than 35 min) in a dynamic adsorption experiment. Importantly, all materials employed in this study were environmentally friendly. In summary, the PLA@CS/HAP filter offers advantages such as ease of preparation, eco-friendliness, versatility, and broad applicability in diverse wastewater treatment scenarios, thereby presenting a significant potential for practical implementation.

A novel double-network hydrogel made from electrolytic manganese slag and polyacrylic acid-polyacrylamide for removal of heavy metals in wastewater

Electrolytic manganese slag (EMS), a bulk waste generated in industrial electrolytic manganese production, can be a cost-effective adsorbent for heavy metals removal after appropriate modification. In this study, EMS was activated by NaOH and then used to make the EMS-based double-network hydrogel (an EMS/PAA hydrogel) via a one-pot method. The results showed that the EMS/PAA hydrogel exhibits a high selective adsorption capacity of 153.85, 113.63 and 54.35 mg·g−1 for Pb (II), Cd (II) and Cu (II), respectively. In addition, Density Functional Theory (DFT) suggests that the adsorption energies (Ead) of Pb, Cd and Cu on SiO2/PAA of the EMS/PAA gels are − 4.15, − 1.96, and − 2.83 eV, respectively, and SiO2/PAA, with a strong affinity to Pb2+, is one of the reasons for the selective adsorption capacity of EMS/PAA gel for Pb2+. The removal efficiency of the EMS/PAA gel for Pb2+, Cd2+, Cu2+ decreased after four adsorption-desorption cycles by 20.00 %, 24.56 % and 46.56 %, respectively. Mechanism studies suggested that the elimination of the heavy metals by EMS/PAA gels mainly involves electrostatic attraction, inner-sphere complexation, and coordination interactions. The EMS/PAA hydrogels not only have high adsorption capacity, but are also easy to prepare and circulate, making them ideal for practical applications.

Adsorption of mercury (II) ions on kaolinite from aqueous solutions: Isothermal, kinetic, and thermodynamic studies

AbstractDue to industrial activity, heavy metal contamination is present in water, air, and soil around the world. Due to this circumstance, serious environmental issues arise. Natural kaolin (NK) clay underwent batch processing to remove Hg2+. Scanner electron microscopy (SEM), energy dispersion spectroscopy (EDS), x‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) were used to analyze the morphological and chemical characteristics of kaolin. Investigations were done into how adsorption is impacted by contact duration, adsorbent dosage, temperature, and solution pH. Kaolin's BET surface area was found to be 8.085 m2/g, while its pore volume was found to be 0.0537 cm3/g. The best working conditions were found to be pH 6.81 and an equilibrium period of 90 min. It was discovered that the Langmuir isotherm model was the most suitable one. At 298, 308, and 318 K, respectively, the adsorption capacities of NK were calculated to be 10.964, 10.515, and 10.101 mg/g. The pseudo‐second‐order kinetic model agreed with this. It was revealed that NK had a maximum desorption efficiency of 91.36%. Through this process, the potential of NK as an eco‐friendly adsorbent for heavy metal removal was shown.

Bentonite Clay as an Alternative Adsorbent for Removal of Heavy Metals in wastewater

This study investigates the potential of bentonite clay as an alternative adsorbent for removing heavy metals from abattoir wastewater. Laboratory experiments were conducted to evaluate the effectiveness of bentonite clay in removing six heavy metals, including Lead, Chromium, Arsenic, Cadmium, Zinc and Iron. Results show that bentonite clay effectively removed all heavy metals, with removal efficiencies ranging from 75% to 95%. The study also found that the adsorption efficiency of bentonite clay increased with increasing initial metal concentration and decreasing pH of the solution. Freundlich and Langmuir models were used to predict the adsorption process, and the R2 values for both models were similar. This suggests that both models were equally adequate or inadequate in describing the process. The study concludes that bentonite clay is a promising adsorbent for removing heavy metals from wastewater. It is recommended that the use of bentonite clay as an alternative adsorbent for heavy metal removal should be further explored and optimized, particularly in terms of operating conditions such as pH, contact time, and adsorbent dosage.  

Use of biochar as a low-cost adsorbent for removal of heavy metals from water and wastewater: A review

In recent years, the removal of heavy metals from water and wastewater systems remains a challenging issue globally. Adsorption technology is widely used for the removal of heavy metals from aquatic systems due to several advantages including its simple operation, low cost and high efficiency. Biochar, which is an environmental benign and low-cost adsorbent, is increasingly used for remediation of heavy metal pollution in aquatic systems. This review critically analyzes recent developments on the biochar-based adsorptive removal of heavy metals from water and wastewater. Biochar is effective for the removal of several toxic metals (As, Cr and Mn) from groundwater and drinking water. Biochar also shows promising performance for the removal of various heavy metals (Cr, Pb, Cu, Cd and Zn) from wastewater. The heavy metal adsorption capacity of the biochar largely depends on the water/wastewater chemistry (pH, competing ions and initial concentrations of adsorbates), contact time between adsorbates and the adsorbent, adsorbent dose and environmental parameters (temperature). The adsorption isotherms and kinetics can be well explained by the Langmuir and pseudo-second order models, respectively. The key mechanisms which drive the heavy metal adsorption onto biochar include precipitation and ion exchange. Biochar-based adsorptive decontamination of heavy metal pollution is sustainable due to low environmental impacts, low energy consumption and low-costs. The key knowledge gaps and future research directions for improvement of biochar-based sorption capacities are highlighted. This review would help for the development of effective biochar-based adsorption technology for the removal of heavy metals from aquatic environments.

Adsorptive removal of heavy metals and organic dyes by sodium alginate/coffee waste composite hydrogel

Heavy metals and dyes used in technological applications have a detrimental influence on human health and the environment. The most used methods for removing pollutants depend on high-cost materials. Therefore, this research was conducted on cost-effective alternatives derived from natural resources and food waste. Herein, we designed a composite hydrogel based on sodium alginate/coffee waste (Alg/coffee) as adsorbent for the removal of organic and inorganic pollutants from aquatic solutions. The selectivity study displayed that Alg/coffee is more effective in adsorbing Pb(II) and acridine orange dye (AO). Adsorption of Pb(II) and AO was studied at concentration range of 0–170 mgL−1 and 0–40 mgL−1. Adsorption data of Pb(II) and AO reveals their fitting to Langmuir-isotherm and pseudo-second-order-kinetic models. The findings demonstrated that Alg/coffee hydrogel are more effective than coffee powder itself with an adsorption (%) approaching 98.44 % of Pb(II) and 80.53 % of AO. Real sample analysis reveals the efficiency of Alg/coffee hydrogel beads in Pb(II) adsorption. The adsorption cycle was examined four times providing high efficiency toward Pb(II) and AO. Desorption of Pb(II) and AO was easily performed using HCl eluent. Thus, Alg/coffee hydrogel beads could be promising adsorbent for the removal of organic and inorganic pollutants.