Initial Cadmium Concentration Research Articles

Eco-efficient cadmium(II) removal from water using alcohol distillate waste: A study of life cycle assessment

This study investigates the use of exhausted grape pomace, a byproduct of alcohol distillation, as a biosorbent for use in removing cadmium(II) from wastewater, in line with principles of a circular economy. Cadmium in water presents substantial environmental and health risks. Conventional treatment methods are often costly and environmentally damaging. This research proposes the use of agro-industrial waste as a sustainable and economical alternative. The biosorption process was optimized with Box-Behnken Design and Response Surface Methodology an adjusting factor such as the cadmium concentration, biosorbent dosage, solution pH, and stirring time. The findings reveal that cadmium(II) removal improves with increased stirring time, reaching a 99 % removal rate at 134 min. Optimal conditions include a biosorbent dosage of 2.4 g, pH 4.7, and initial cadmium concentration of 55 mg/L. The biosorption process also increased the solution’s pH, ensuring compliance with wastewater discharge regulations. Two optimization scenarios were evaluated. One achieved a 99.99 % removal efficiency for maximum cadmium reduction, The second focused on cost-effectiveness and environmental impact, attaining 77.35 % removal. This scenario highlights reduced the environmental impact, thereby supporting the role of exhausted grape pomace as a viable and eco-friendly option for wastewater treatment. Life cycle analysis, using CML-IA mid-point and ReCiPe end-point indicators, further underscores the sustainability of this approach, affirming the potential of grape pomace to contribute to circular, resource-efficient wastewater management.

Adsorptive removal of cadmium (II) from wastewater using activated carbon synthesized from stem of Khat (Catha edulis)

IntroductionCadmium is among the most hazardous heavy metals, posing the greatest risk to human beings and the environment. Adsorption with activated carbon prepared from agricultural waste is the most effective way to remove cadmium (II) from wastewater. In this study, activated carbon prepared from the stem of Khat (Catha edulis) plant was used for the removal of cadmium (II) from wastewater. ObjectiveTo evaluate the efficiency and mechanism of the removal of cadmium (II) from wastewater using Khat (Catha edulis) stem activated carbon at different operating parameters. MethodProximate and Fourier transform infrared analyses were conducted to characterise the prepared Khat stem-activated carbon. The effects of initial cadmium concentration, adsorbent dose, pH, contact time, and agitation speed on the cadmium removal efficiency of Khat stem-activated carbon were evaluated. Furthermore, isotherm and kinetic models of adsorption were used to evaluate the mechanism of cadmium removal. ResultThe proximate analysis indicated that the activated carbon derived from Khat stems possesses a bulk density of 0.58 g/cm3 and surface area of 615 m2/g. Additionally, the prepared Khat stem activated carbon has 4 %, 14 %, and 22 % of moisture content, ash content, and volatile matter, respectively. Furthermore, the proximate analysis indicated that the Khat stem activated carbon has a porosity of 55 %. The Fourier transformed infrared spectroscopy result indicated the presence of phenolic, alcoholic, and carboxylic acid functional groups on the surface of Khat stem activated carbon. The experimental data showed a better fit with the Langmuir isotherm model (R-squared and chi-square value of 0.9727 and 1.3936, respectively) and the pseudo-second-order kinetic model (R-squared and chi-square values of 0.9032 and 0.2179, respectively). The highest adsorption efficiency of cadmium (97 %) was attained at an adsorbent dose of 0.125 g, a contact time of 30 min, an initial cadmium concentration of 20 mg/L, a pH of 5, and an agitation speed of 100 rpm at room temperature (25 °C). ConclusionThe results obtained in this research demonstrated that activated carbon from Khat stems can be employed as an economical, ecologically friendly, easily accessible and efficient activated carbon to remove Cd (II) from wastewater.

A synergistic integration of life cycle assessment and response surface methodology to optimize grape stalk waste-based biosorption for effective Cd(II) removal

In order to remove Cd(II) ions from aqueous solutions, this research suggests an in-depth study on a laboratory scale for the efficient and sustainable removal of Cd(II) in aqueous solution using wine industry grape stalk waste. The maximum biosorption capacity that was achieved was 84.74 mg/g for the Langmuir isotherm model. The kinetic studies revealed that the biosorption data were better explained by a pseudo-second order model. By using the response surface method with desirability functions, the optimal variables were determined for three optimization scenarios. The first optimization scenario yielded the highest percentage of cadmium removal, reaching 87.75%. The goal of that scenario was intended to obtain the maximum percentage of cadmium removal while minimizing the cost of the process. In this scenario, the greatest environmental impact was on the marine aquatic ecotoxicity (2.685 kg 1.4 DB eq.) with a power consumption of 27.05 W. Furthermore, the values for the input variables were an initial cadmium concentration of 0.6 mg/l, pH of 7.5, stirring time of 10 min, stirring speed of 100 rpm, a process temperature of 15 °C, and a dose of grape stalk of 0.50 g. The experimental and predicted findings agree. This suggests that grape stalk waste has potential applications as a biosorbent for the removal of Cd(II) ions from aqueous solution.

Applying circular economy principles and life cycle assessment: A novel approach using vine shoots waste for cadmium removal from water

This research investigates the potential of utilizing vine shoots, a byproduct of the viticulture industry, as biosorbent for cadmium removal from aqueous solutions. The Spanish wine industry, one of the most influential sectors, produces two to three million tons of vine shoots. By using vine shoots as biosorbent, this study contributes to the circular economy paradigm, transforming waste materials into valuable resources and minimizing environmental impacts associated with waste generation and disposal. The research underscores the significance of vine shoots in biosorption due to its high lignocellulosic content. By experimental analysis, the efficacy of vine shoots in cadmium biosorption is evaluated, considering factors such as environmental impact or energy consumption. This study examines the effect of six key input parameters on cadmium removal efficiency and power consumption, identifying optimal conditions for maximum removal with minimal energy consumption. The findings suggest that vine shoots offer promising biosorption capabilities, promoting sustainability in wastewater treatment and environmental remediation efforts. By employing the response surface method alongside desirability functions, the study determined the optimal variables for two distinct optimization scenarios. Notably, in the second optimization scenario, a cadmium removal rate of 99.23 % was achieved while consuming 25.6 W of power. The input parameters for this achievement should be set as follows: initial cadmium concentration of 100 ppm, pH level of 8, stirring time of 75 min, stirring speed of 100 rpm, temperature of 26 °C, and a dose of vine shoots of 0.1 g.

Optimization of fenugreek seed mucilage extraction for the synthesis of a novel bio-nano composite for efficient removal of cadmium ions from aqueous environments

This research investigates the application of an innovative bio-nanocomposite, Fenugreek seed mucilage/silicon carbide (FSM/SiC), as an exceptionally effective adsorbent for eliminating cadmium ions from aqueous solutions. Optimization of fenugreek mucilage extraction involved ultrasonic methods, establishing ideal conditions with a solid-to-solvent ratio of 1:55, 50 °C temperature, 37 kHz frequency, 100 % power, and 30 min processing time. Comprehensive characterization through FTIR spectroscopy, XRD, imaging, DLS, and SEM confirmed the preservation of crucial adsorption-related characteristics. Enhanced adsorption efficiency was achieved by systematically adjusting pH, temperature, adsorbent concentration, pollutant concentration, and contact time, identifying optimal conditions at pH 6, 0.03 g adsorbent dosage, 35 min contact time, and 30 mg/L initial cadmium concentration at 30 °C. Adsorption kinetics followed a pseudo-second-order model, while the Langmuir isotherm fit suggested monolayered adsorption. Thermodynamic analysis indicated exothermic and spontaneous Cd2+ ion adsorption onto FSM/SiC. Remarkably, FSM/SiC demonstrated exceptional regeneration potential, positioning it as a promising solution for water decontamination and environmental remediation. This research showcases FSM/SiC's potential with a maximum adsorption capacity of 41.6 mg/g for cadmium ions, highlighting its significance in addressing cadmium contamination.

Bolivian natural zeolite as a low-cost adsorbent for the adsorption of cadmium: Isotherms and kinetics

Population growth in recent years has led to increased wastewater production and pollution of water resources. This situation also heavily affects Bolivia, so wastewater treatment methods and materials suitable for Bolivian society should be explored. This study investigated the natural Bolivian Zeolite (BZ) and its NaCl-modified structure (NaBZ) as adsorbents for cadmium removal from water. The natural BZ and the modified form NaBZ were investigated by different physicochemical characterization techniques. Furthermore, XPS and FT-IR techniques were used to investigate the adsorption mechanisms. The cadmium adsorption on BZ and NaBZ was analyzed using various mathematical models, and the Langmuir model provided a better description of the experimental adsorption data with cadmium adsorption capacities of 20.2 and 25.6 mg/g for BZ and NaBZ, respectively. The adsorption followed the pseudo-second order kinetics. The effect of different parameters, such as initial cadmium concentration and pH on the adsorption was studied. In addition, the results of the regeneration test indicated that both BZ and NaBZ can be regenerated by using hydrochloric acid (HCl). Finally, the adsorption experiment of BZ and NaBZ on a real water sample (brine from Salar de Uyuni salt flat) containing a mixture of different heavy metals was carried out. The results obtained in this study demonstrate the effectiveness of natural BZ and modified NaBZ in the removal of heavy metals from wastewater.

Cadmium Removal from Synthetic Aqueous Solutions by Adsorption on Peanut Shells: Kinetic and Thermodynamic Studies

Peanut shells were used in this study as an adsorbent carrier in the treatment of wastewater containing a trace metal element (TME), namely cadmium, a pollutant with adverse effects on health and the environment. The influences of contact time between adsorbent and adsorbate, initial cadmium concentration, adsorbent mass, reaction medium temperature and solution pH were evaluated. To determine the optimum parameters, pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental results of the contact time study. Similarly, experimental results relating to the influence of concentration and temperature were modeled. Modeling of the data from the adsorbate-adsorbent contact time study showed that the kinetics of the cadmium adsorption reaction are well described by the pseudo-second-order kinetic model. The isotherm of the adsorption mechanism of cadmium ions (Cd2+) by peanut shells is perfectly described by the Freundlich equation. Thermodynamic studies using temperature variation have shown that adsorption is spontaneous and endothermic. This study led to a low entropy during cadmium adsorption. The best adsorption capacity was obtained at low pH = 5, i.e. favorable adsorption in acidic media.

Optimization of cadmium adsorption on metal organic frameworks MIL-53(Fe) using response surface methodology

This research aims to optimize the cadmium adsorption on metal organic frameworks MIL-53(Fe) using response surface methodology. Specifically, the effects of the adsorption parameters, such as contact time, initial cadmium ion concentration and adsorbent dosage were examined. The experimental design and optimization process consisted of a central composite design and a response surface analysis. The adsorption experimental data were analyzed to validate the the quadratic model produced by the response surface methodology. The results indicated that the interaction between contact time and initial cadmium ion concentration affects the cadmium uptake. The maximum cadmium uptake was obtained at the optimum conditions of 85 min contact time, 46 mg adsorbent dosage and 10 mg/L initial concentration of cadmium. A maximum of 74.94% adsorption efficiency was achieved under optimum conditions, with an F-value of 65.37. The model fitting was satisfactory, as the correlation coefficient of experimental (0.9882) and predicted (0.9731) was in good agreement. This study demonstrates the effectiveness of a combined application of central composite design and response surface methodology in evaluating the effects of the factors influencing cadmium adsorption adsorption on MIL-53(Fe).

Novel oligonucleotide-based sorbent for the selective extraction of cadmium from serum samples

The objective was to develop a sorbent functionalized with aptamers for the selective extraction of cadmium from biological samples. Two oligonucleotide sequences reported in literature as specific to cadmium were covalently grafted on activated Sepharose, with grafting yields of 45%. Once the supports packed in cartridges, a thorough study of the percolation conditions favoring Cd(II) retention was performed, demonstrating the importance of the nature of this medium. A high selectivity was reached when applying the optimal conditions as a recovery of 85% was obtained using the sorbent functionalized with one of the specific aptamers and only 1% on the control sorbent grafted with a scramble sequence. A high specificity was also obtained as recoveries for most of other ions were lower than 15%. The capacity of this oligosorbent estimated to 180 ng of Cd(II) for 30 mg of support was perfectly adapted to the trace analysis of Cd(II). The extraction procedure was then applied to a serum sample which was first subjected to acid precipitation. The initial concentration of cadmium in the serum was estimated to 1.83 µg/L using standard addition method and an extraction yield of 75 ± 1.6% was measured. Comparison of these results with those obtained without oligoextraction (recovery of 57%) showed a significant reduction of matrix effects in ICP-MS thanks to the use of the oligosorbent, underlining its interest for a more reliable quantification of Cd(II). This result was confirmed by performing the oligoextraction protocol on a certified serum.

Response Surface Methodology for the Optimization of Cadmium Ion Adsorption using Activated Carbon

Adsorption refers to the process of chemical species adhering to the surface of particles. Activated carbon, also known as activated charcoal, is a type of carbon widely utilized for purifying water and air by filtering out various contaminants. One of the transition metals, Cadmium (Cd), situated in the dblock and 12th group of the periodic table, possesses toxic and poisonous properties. Absorbent material was prepared using standard method. The absorbate was prepared by dissolving cadmium nitrate in distilled water. Different volume of the solution was added absorbate and later filtered and atomic adsorption Spectroscopy (AAS) was carried out. The potential of Activated carbon for removal of cadmium from contaminated water, it was found that highest efficiency in terms of percentage removal was achieved at 50 ppm initial metal ion concentration of Cadmium. The highest percentage removal was 98.5% confidence level. Therefore, the hypothesis that Activated carbon adsorbents are effective in removal of cadmium (II) ion from contaminated water at different experimental conditions is upheld

Biosorption of cadmium by Enterobacter ludwigii isolated from soil contaminated with cadmium near a coal-fired power plant in Korea

ABSTRACT This study aimed to isolate and characterize indigenous bacteria from cadmium-contaminated soil around a coal-fired power plant in Korea for their potential use in biosorption. The 16S ribosomal RNA analysis identified Enterobacter ludwigii G17–1 in the soil, exhibiting a remarkably high minimum inhibitory concentration (2,500 mg/L) for cadmium. The efficiency of cadmium biosorption was investigated under different pH levels (6–9), temperatures (15–40°C), and initial cadmium concentrations (25–100 mg/L), using both live and dead G17–1. The live G17–1 strain exhibited a maximum biosorption efficiency of 50% for 25 mg/L cadmium at 24 hours, while the highest efficiency achieved with dead G17–1 was 48% at 1 hour. The biosorption capacity decreased as the initial cadmium concentration increased. These findings suggest that the isolated bacterium, E. ludwigii G17–1, holds potential for the bioremediation of cadmium-contaminated water and wastewater.

MODELLING AND OPTIMIZATION OF CADMIUM REMOVAL FROM WASTEWATER ONTO SUGARCANE BAGASSE ACTIVATED CARBON

The presence of sugarcane bagasse as an agricultural waste in the environment is a cause for concern as it defaces the environment. It is bulky and difficult to manage. This prompt the need to research into the reuse of sugarcane bagasse in a more rewarding way, thereby saving the environment from its litters. In this study, Sugarcane bagasse was collected from Gaskiya Road in Zaria and converted to activated carbon using thermal and chemical methods. The Sugarcane bagasse was divided into three portions and carbonized at temperatures of 300, 325 and 350oC and then chemically modified with 1M H3PO4 acid at ratio of 1:2. Batch adsorption experiments were carried out using three input variables: adsorbent dosages of 0.2 - 1.0 g; initial cadmium concentrations of 5 - 25 mg/l and carbonization temperatures of 300 - 350 oC with the corresponding output variables of removal efficiency (X1) and adsorption capacity (X2). The experimental data were modeled, optimized and validated using Response Surface Methodology (RSM). The optimum operating conditions for adsorption of cadmium onto sugarcane bagasse activated carbon were: carbonization temperature of 300 oC, initial cadmium concentration of 25 mg/l and adsorbent dosage of 1.0 g with the corresponding optimized removal efficiency and adsorption capacity of 100% and 2.5mg/g, respectively. The optimized removal efficiency and adsorption capacity were validated and the errors of 0.000 and 0.009%, respectively were recorded. It was concluded that sugarcane bagasse was effective in the removal of cadmium from wastewater and hence its reuse as an adsorbent in wastewater treatment is a viable waste management option. Also the model developed had proven to be valid in predicting the output variables.

Removal of toxic cadmium (II) from zinc sulfate solution with zinc powder enhanced by ultrasound: Kinetics and mechanism

Currently, removing cadmium (II) from zinc sulfate electrolytes using zinc powder presents several problems, such as the agglomeration and encapsulation of the zinc powder, which leads to increased consumption of the zinc powder and poor removal performance. To overcome this limitation, ultrasound is used to assist the replacement of the zinc powder to remove cadmium (II) from zinc sulfate electrolytes. Compared with conventional replacements, the ultrasonic-assisted replacements reduce the reaction time from 120 to 40 min, the reaction temperature from 60 to 55 ℃, and the required amount of zinc powder from 5 to 3 g/L. Under the same process conditions, the replacement rate of cadmium (II) is increased from 68.9 to 98.7 %. According to kinetic studies, ultrasound reduces the required activation energy for replacement from 34.77 to 16.83 kJ/mol, which significantly reduces the energy barrier of the cadmium precipitation. In addition, ultrasound can remove the reaction layer between the zinc powder and cadmium (II), thus accelerating the chemical reaction rate. The kinetic behavior changes when the initial cadmium (II) concentration is in the range of 800–1200 mg/L in conventional experiments, and 1600–2000 mg/L in ultrasound experiments. The characterization of the purification slags confirms that ultrasound can refine particles, improve the replacement rate of cadmium (II), and significantly reduce the consumption of the zinc powder. The ultrasound-enhanced purifying technology of zinc sulfate electrolytes with zinc powder is of great significance for zinc electrowinning and comprehensive recovery of cadmium.

Cadmium Removal Using Bio-Electrochemical Reactor with Packed Bed Rotating Cylindrical Cathode: A Kinetics Study

The kinetics of removing cadmium from aqueous solutions was studied using a bio-electrochemical reactor with a packed bed rotating cylindrical cathode. The effect of applied voltage, initial concentration of cadmium, cathode rotation speed, and pH on the reaction rate constant (k) was studied. The results showed that the cathodic deposition occurred under the control of mass transfer for all applied voltage values ​​used in this research. Accordingly, the relationship between logarithmic concentration gradient with time can be represented by a first-order kinetic rate equation. It was found that the rate constant (k) depends on the applied voltage, the initial cadmium concentration, the pH and the rotational speed of cathode. It was increased with increasing the applied voltage and its relationship with the applied voltage obeyed an exponential formula. The rate constant (k) was decreased with increasing the initial concentration of cadmium higher than 150ppm while at low concentrations it was increased. pH and rotational speed have different effects on the rate constant. Increasing the pH from 3 to 6 increases the rate constant while a slight decrease in the rate constant occurs at pH = 7. Increasing the rotation from 100 to 500 rpm increases the rate constant; however, the rate constant became approximately constant buoyed 300 rpm.

Elaboration, characterization and performance evaluation of a new environmentally friendly adsorbent material based on the reed filter (Typha Latifolia): Kinetic and thermodynamic studies and application in the adsorption of Cd (II) ion

• The kinetic study, at constant temperature, shows that the extraction yield and the sorption capacity of Cd (II) on the resin increase rapidly with time, the equilibrium is reached after 40 min for raw reeds (RB) and 60 min for treated reeds (RS). • The adsorption capacity increases with the increase of the initial cadmium concentration and reaches a maximum equal to mg g −1 at a concentration higher or equal to 26.35 mg g −1 and 40.01 mg g −1 , respectively for RB and RS. • This retention capacity is very important which shows that this resin has a high affinity towards cadmium. • The application of the Langmuir and Freundlich adsorption models showed that the Langmuir isotherm better describes the adsorption of Cd (II) on the resin. Heavy metal pollution is a public health problem that should prompt environmental protection authorities to provide appropriate solutions. The objective of this work concerns the liquid-solid extraction of Cadmium by the filtering resin of raw RB and modified RS reeds. The experimental study clarified the influence of some operating parameters. The results of the experiments show that the adsorption process depends on several parameters: the presence of salts, the temperature and the pH of the medium. Equilibrium is reached after 40 min for raw reeds (RB) and 60 min for treated reeds (RS). The pH of the aqueous phase, optimal for this extraction is between 4.5 and 6.0, increasing the temperature of the aqueous phase-adsorbate mixture from 25 to 65 °C decreases the extraction yield and the sorption capacity. The pseudo-second order kinetic model and Langmuir model are the most adequate to describe the adsorption process and the adsorption capacity increases with the increase of initial cadmium. Concentration and reaches a maximum equal to 26.35 mg g −1 and 40.01 mg g −1 , respectively for RB and RS. The thermodynamic study showed that the retention process is spontaneous and exothermic. The cadmium metal Cd (II) adsorption mechanism was also interpreted by spectroscopy FTIR and energy-dispersive X-ray (EDX). Dramatically, the introduction of the chemical treatment allows the increase of the content of activated functional groups in the resin, leading to a higher amount of adsorption on Cd (II). The desorption might of the resin depended on the various parameters like HNO 3 concentration, desorption of the temperature and time. The satisfactory desorption of the capacity and efficiency is 69% RB and 92% RS. Based on these results, RB and RS acid-treated products could be utilized as low-cost, environmentally friendly and effective adsorbents for Cd (II) elimination from water. The various parameters thermodynamic such as ∆G°, ∆S° and ∆H° showed that the adsorption process was feasible, spontaneous and exothermic.

Adsorption and removal studies of cadmium ion onto sulphonic/phosphonic acid functionalization resins

AbstractCadmium is a persistent bio‐accumulative toxic metallic element, which causes hazardous impacts on living species, water, and the environment. This paper presents the study of cadmium ion removal from aqueous solutions in batch experiments using 22 ion exchange resins with different functional groups. It was found that Dowex G‐26 resin with a sulphonic functional group and Puromet™ MTS9570 resin with sulphonic and phosphonic functional groups had excellent performance for Cd (II) ion removal. The effects of resin dosage, adsorption time, initial concentration of cadmium, and initial pH of solution on cadmium removal were investigated systematically using Dowex G‐26 and Puromet™ MTS9570 resins. Maximum cadmium removal rates of 99.2% and 98.9% were achieved for G‐26 and MTS9570, respectively, at an initial cadmium concentration of 1000 mg/L, an initial solution pH of 5.0, an adsorption time of 30 min, and a 0.01 mg/L resin dosage for G‐26, and a 0.025 mg/L resin dosage for MTS9570. The ion‐exchange adsorption process was fast, and it reached equilibrium after 30 min of adsorption. The results obtained show that both resins performed well for the removal of Cd (II) ions from weakly acidic solutions. Langmuir, Freundlich, and Temkin isotherms models were employed to investigate and understand the adsorption characteristics. The results showed that the studied adsorption processes fitted well to the Langmuir adsorption isotherm. From the Langmuir adsorption isotherm, the maximum adsorption capacities of Cd (II) were found to be 78.125 and 51.020 mg/g for G‐26 and MTS9570, respectively. This research provides an efficient systemic approach for cadmium ion removal from aqueous solutions.

Magnetite-induced topological transformation of 3D hierarchical MgAl layered double hydroxides to highly dispersed 2D magnetic hetero-nanosheets for effective removal of cadmium ions from aqueous solutions

The study shows the synthesis of highly dispersed magnetic hetero-nanosheets through topological transformation of 3D Hierarchical MgAl layered double hydroxides in the presence of Fe3O4 nanoparticles. The platelet-like hierarchical nano-heterostructures consisted of 10 nm Fe3O4 magnetic nanoparticles dispersed over the surface of MgAl-LDH lamella. The as-prepared biphasic self-assembled nanocomposite was successfully used as an adsorbent for decontamination of spiked cadmium wastewater at room temperature. A comprehensive physico-chemical characterization of structural and textural features, as well as the magnetic properties of the prepared nanocomposites were carried out by using complementary techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), Dynamic light scattering (DLS) analysis, Brunauer-Emmett-Teller (BET) surface area and Zeta potential respectively. Moreover, the influences of certain parameters including pH, adsorbent dosage, initial cadmium concentration, and contact time were extensively studied in terms of profiling the adsorption capacity of the hierarchical nano-heterostructures. Different adsorption isotherm (Langmuir, Freundlich, Temkin, and Redlich-Peterson) in linear and nonlinear forms were applied. According to the results, Freundlich and Redlich-Peterson models fitted the data. On the other hand, three kinetic models were used, including pseudo-first order, pseudo-second order (linear and nonlinear forms), and intraparticle diffusion.The results were explained through a pseudo-second-order model, reaching the equilibrium in 60 min. The optimum recommended pH and adsorbent dose are 5 and 1.4 g/L, respectively. Comprehensive characterization revealed that the synthesized materials are suitable candidates as adsorbents in Cd (II) adsorption techniques with maximum adsorption capacities of 80.6 mg/g, 91.7 mg/g, and 109.9 mg/g. Furthermore, the regeneration investigation highlighted the adsorbents' performance after three cycles of adsorption/desorption.

Process optimization and modeling of Cd2+ biosorption onto the free and immobilized Turbinaria ornata using Box\u2013Behnken experimental design

The release of effluents containing cadmium ions into aquatic ecosystems is hazardous to humans and marine organisms. In the current investigation, biosorption of Cd2+ ions from aqueous solutions by freely suspended and immobilized Turbinaria ornata biomasses was studied. Compared to free cells (94.34%), the maximum Cd2+ removal efficiency reached 98.65% for immobilized cells obtained via Box–Behnken design under optimized conditions comprising algal doses of 5.04 g L−1 and 4.96 g L−1, pH values of 5.06 and 6.84, and initial cadmium concentrations of 25.2 mg L−1 and 26.19 mg L−1, respectively. Langmuir, Freundlich, and Temkin isotherm models were suitably applied, providing the best suit of data for free and immobilized cells, but the Dubinin–Radushkevich model only matched the immobilized algal biomass. The maximum biosorption capacity of Cd2+ ions increased with the immobilized cells (29.6 mg g−1) compared to free cells (23.9 mg g−1). The Cd2+ biosorption data obtained for both biomasses followed pseudo-second-order and Elovich kinetic models. In addition, the biosorption process is controlled by film diffusion followed by intra-particle diffusion. Cd2+ biosorption onto the free and immobilized biomasses was spontaneous, feasible, and endothermic in nature, according to the determined thermodynamic parameters. The algal biomass was further examined via SEM/EDX and FTIR before and after Cd2+ biosorption. SEM/EDX analysis revealed Cd2+ ion binding onto the algal surface. Additionally, FTIR analysis confirmed the presence of numerous functional groups (hydroxyl, carboxyl, amine, phosphate, etc.) participating in Cd2+ biosorption. This study verified that immobilized algal biomasses constitute a cost-effective and favorable biosorbent material for heavy metal removal from ecosystems.

Curvularia coatesiae XK8, a Potential Bioadsorbent Material for Adsorbing Cd(II) and Sb(III) Compound Pollution: Characteristics and Effects.

Soil heavy metal pollution is a common problem in mining areas. The soil of the Xikuangshan located in Lengshuijiang, Hunan Province, China contains various excessive heavy metals, especially antimony and cadmium. Previous studies have shown that heavy metal-tolerant microorganisms screened from mining areas have the potential to adsorb heavy metals. In this study, we screened out a cadmium and antimony tolerant fungus named XK8 from the slags collected from the Xikuangshan. Then, we explored the single and binary biosorption characteristics of Cd(II) and Sb(III) on it. In our results, the fungus XK8 was identified as Curvularia coatesiae XK8 by ITS sequencing analysis. Under the optimal conditions, in binary biosorption of the XK8, the main effect of the initial cadmium concentration on the cadmium removal rate of XK8 is negative, while the main effect of the initial antimony concentration, biosorption time, and initial pH on the cadmium removal rate of XK8 is positive. The initial pH has the greatest impact on the biosorption of cadmium on XK8, followed by the biosorption time; moreover, the effects of both are stronger than the coexisting ions. SAS analysis shows that under the optimal conditions, the theoretical maximum cadmium removal rate of XK8 is 100%, and the actual removal rate is 67.57%. Compared to the single biosorption with binary biosorption, the maximum biosorption capacity of XK8 for cadmium in the composite biosorption system increased to 23.6 mg g–1. It shows that under the background of high antimony, Sb(III) has a promoting effect on the biosorption of Cd(II) on XK8. In summary, a cadmium and antimony tolerant fungus with strong cadmium biosorption ability under the background of high antimony was screened out. It provides a potential microbial material for the bioremediation of heavy metal pollution.

ADSORPTION OF Cd(II) IN A SEMI-CONTINUOUS PROCESS BY RESIDUAL CHARCOAL FROM THE PYROLYZED OIL PALM SHELLS

This study aims to evaluate the utilization of residual charcoal from the pyrolysis of oil palm shells as activated carbon for the adsorption of cadmium metal ions in a semi-continuous process. The charcoal was crushed with a ball mill to a size of 80-100 mesh and its activation was carried out chemically using 0.1 N NaOH. Cadmium metal ions were adsorbed in a semi-continuous operation using a cylindrical packed bed column, with variations in the inlet feed concentration, pH, column inside diameter, bed height, and flow rate. The initial concentration of cadmium before and after the adsorption was tested on an atomic absorption spectrophotometer. The adsorption isotherms were evaluated using the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm models. The results showed that the best adsorption capacity was obtained at an initial concentration of 120 mg/L, pH 5, inside diameter of 26 mm, bed height of 50 cm, and flow rate of 10 ml/min. The isotherm model of cadmium metal ion adsorption followed the Langmuir isotherm with R2 = 0.99.