Initial Cadmium Concentration Research Articles

Enhanced removal of cadmium from water using bio-sorbents synthesized from branches and leaves of Capparis decidua and Ziziphus mauritiana

In this work, powdered adsorbents synthesized from branches and leaves of Capparis decidua (CDB) and Ziziphus mauritiana (ZML) are used for the remediation of potentially toxic cadmium (Cd(II)) ions from wastewater. The effects of various operating parameters such as adsorbent dosage, pH, temperature, contact time and initial concentration of cadmium on the adsorption process were evaluated. The maximum adsorption capacity of CDB and ZML was 248.62 mg/g and 235.65 mg/g, respectively, for Cd(II) ions at room temperature, when the optimum pH, adsorbent dosage, contact time and concentration of Cd(II) were 6.0, 0.1 g/100mL, 60 min and 249 mg/L, respectively. Kinetic studies revealed that the bio-sorption process follows a pseudo-second order model (R 2 = 0 . 999 ) for both employed sorbents. The equilibrium data were found to be in good agreement with Freundlich and Langmuir adsorption isotherm in the case of C. decidua and Z. mauritiana, respectively. Thermodynamic analysis revealed that Cd(II) adsorption onto both bio-sorbents was spontaneous and exothermic in nature. The prepared adsorbents also exhibited excellent regeneration potential with a minor loss in the adsorption capacities after six cycles. • Plant-based adsorbents were employed for the removal of Cd(II) ions from water. • The q m of CDB and ZML was 248.62 and 235.65 mg/g , respectively, for Cd(II) ions. • The adsorption process follows a pseudo-second order kinetic model (R 2 = 0.999). • The prepared adsorbents showed excellent regeneration potential up to six cycles.

Synthesis and characterization of iron oxide/MIL-101 composite via microwave solvothermal treatment

Fe3O4/Fe2O3-MIL-101 synthesized using carboxylated Fe3O4/Fe2O3, chromium nitrate nonahydrate, terephthalic acid under microwave irradiation. A new composite, i.e. Fe3O4/Fe2O3-MIL-101-NH2 was also synthesized under microwave irradiation condition. The composites were characterized with the help of XRD, FT-IR, SEM, EDX, TEM, DSC/TGA and VSM. XRD analysis depicts preservation of iron oxide and MIL-101 peaks in the composite, i.e. Fe3O4/Fe2O3-MIL-101. The transformation of Fe3O4/Fe2O3-MIL-101 to Fe3O4/Fe2O3-MIL-101-NH2 occurred with a decline in the organic content of the product. The EDX analysis depicted the presence of both chromium and iron in both composites. Ferromagnetic nature of both the composites ascertained with the VSM analysis. The Fe3O4/Fe2O3-MIL-101 depicted low adsorption capacity for both cadmium (2.79 mg/g or 41.17 % removal at initial cadmium concentration of 6.8 mg/l) and nickel (1.29 mg/g or 16.88 % removal at initial nickel concentration of 7.7 mg/l). The Fe3O4/Fe2O3-MIL-101 did not show any zone of inhibition with different bacteria during the ecotoxicity study.

Optimization of Cadmium Ions Biosorption Onto Trichoderma Fungi

Cadmium (Cd) is one of the heavy metal ions and environmental pollutants that can harm humans and other organisms by eliminating serious toxic effects even at low concentrations. Nowadays, the use of this element in various industries has increased its concentration in the environment. Therefore, it is necessary to find appropriate and practical ways to remove it from the environment. The purpose of this study is to evaluate the efficiency of Trichoderma in the absorption of cadmium ions from an aqueous solution by a central composite design (CCD) to optimize the experimental conditions. Analysis of variance (ANOVA) was performed to study the importance and effectiveness of the model. Design specialist software reviewed four independent variables: pH, mixing rate, contact time, temperature, and initial cadmium concentration. A second-order quadratic model was developed to predict the reactions. An ANOVA of cadmium decay in solutions by Trichoderma shows an F-value of 6655.67 for the quadratic model, which indicates that the model is significant. CCD was able to provide a statistical model for predicting response with high accuracy and reliability. Under optimal conditions, the average cadmium decrease (pH = 6, contact time of 120 minutes, initial concentration of cadmium ions of 25° C and 25 mg/L) is approximately 98.8%.

Expulsion of cadmium from a simulated wastewater using CKD as adsorbent: Optimization with isotherm study

Cement kiln dust (CKD) considers as an inexpensive, abundant adsorbent and was used in the present work for removing cadmium ions from a simulated wastewater. CKD was obtained from Al-Duh Cement Factory located in south of Al-Muthanna Governorate/Iraq and identified by X-ray diffractometer (XRD), scanning electron microscopy (SEM) with EDX, and Fourier transform infrared spectrometry (FTIR). Optimization of the main effective parameters like initial cadmium concentration, CKD dosage, shaking speed, pH and contact time on the cadmium removal efficiency was achieved via applying reaction surface strategy (RSM). Results showed that underlying cadmium fixation has the fundamental impact on the cadmium removal efficiency followed by CKD dosage, time, pH, and lastly shaking speed. The preferred operating conditions were found to be an initial Cd concentration of 20 ppm, CKD dosage of 35 g \ L, pH of 8, shaking speed of 300 rpm, and contact time of 90 minutes. Based on these optimum conditions, 99.75% removal efficiency of cadmium was obtained. The adsorption isotherm results showed that the adsorption behavior of Cd ions on CKD agree well with Langmuir model. CKD seems to be a systematic, sustainable and economic material for cadmium removal from wastewater.

Cadmium ions adsorption from aqueous solutions by Bentonite clay, fixed bed column

Cadmium metal is discharged to the water from different industries. It can cause serious troubles for human being and aquatic ecosystems. The adsorption technique applied in this study to remove cadmium from simulated aqueous solutions onto bentonite clay by various experiments. Fixed bed system was implemented to verify the Impact of pH, initial cadmium concentration, adsorbent bed height, flow rates and the treatment time on cadmium ions removal. The results show up that when the pH of the aqueous solution was lowered, the cadmium removal efficiency increased. The cadmium removal efficiency decreased due to the increased initial cadmium concentration. Experiments have shown that increasing the contact time and the adsorbent medium in the column lead to more removal efficiency. Removal efficiency increased when the flow rate decreased. The best removal efficacy was (80%) when the pH of (3), initials cadmium concentration (3mg/l), height of the adsorbent bed (50 cm), flow rates (10 ml/min.) and the treatment time of (120 min.). Finally, the bentonite clay can be used for cadmium ions removal instead of more expensive adsorbents, because of its low cost, availability and perfect adsorption property..

Synthesis of polystyrene-based hyper-cross-linked polymers for Cd(II) ions removal from aqueous solutions: Experimental and RSM modeling

The hyper-cross-linked polymers (HCPs) based on the polystyrene was synthesized during the Friedel-Craft reaction in various situations. The HCPs synthesis were carried out in various operating conditions including reaction time in the range of 3–23 h, the ratio of cross-linker to monomer in range of 1–5 at temperature of 80 ℃. In addition, the cadmium adsorption process was carried out at a temperature in the range of 25–85 ℃ and initial cadmium concentration in the range of 10–100 mg/L. The response surface methodology (RSM) has been applied for optimizing the process using synthesis and adsorption parameters. The optimized synthesis conditions were obtained 3.32, 11.26 h, 80 ℃, in ratio, synthesis time, and temperature, respectively. Also, the optimized adsorption conditions were obtained 80 mg/L and 35 ℃, initial cadmium ion concentration, and temperature, respectively. The surface area and thermal stability were obtained at 853.89 m2/g and 450 ℃, respectively. The maximum adsorption capacity and removal efficiency had been obtained 950 mg/g and 92% at a temperature of 20 ℃, after 80 min, respectively. The maximum adsorption capacity and removal efficiency were observed in the initial concentration of 120 mg/L and 10 mg/L, respectively. The adsorption process behavior was surveyed using isotherm, kinetic and thermodynamic models. The isotherm results showed that the adsorption of cadmium by HCPs is multi-layer and heterogeneous. The thermodynamic parameters showed that the process is exothermic and spontaneous. Finally, the kinetic results showed that the process occurred physically and slowly as the temperature raised.

Modelling and efficiency assessment of the up flow fixed bed process packed with Moringa oleifera for continuous Cd(II) removal from drinking water

The biosorption ability of ‘Moringa oleifera ‘seed powder for the expulsion of cadmium from wastewater was investigated by performing packed column tests. Column tests were conducted as a function of biosorbent dose, influent flow rate and feed sorbate concentration. The findings from column operations revealed that values of maximum cadmium uptake, exhaustion and breakthrough time enhances with rise in bed depth, reduces with rise in feed volumetric flowrate and initial cadmium concentration. At 6 g of Moringa oleifera dose, 2 mL/min of flow rate and 300 µg/L of influent cadmium, the cadmium uptake capacity was found to be 65.44, µg/g. The continuous packed column data for cadmium were well fitted to the Thomas model with the regression coefficient ranges 0.966–0.993. Moreover, the qth values obtained from Thomas model are similar to the experimental breakthrough capacities qexp. The FTIR results reveals that the Moringa oleifera seed contains various active functional groups which are appears to be played a significant role in biosorption of cadmium ions. From practical view, the Moringa oleifera seed could be utilized as safe, inexpensive, sustainable and eco-friendly biosorbent for the elimination of cadmium from drinking water using continuous column mode and also this technology could be considered as an ideal for household usage in rural communities.

METODOLOGIA DE SUPERFÍCIE DE RESPOSTA PARA OTIMIZAÇÃO DA ADSORÇÃO DE METAIS PESADOS EM UMA SOLUÇÃO MULTI-METAIS POR PELLETS DE ZEÓLITAS DE BENTONITA-CAOLIM

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb > Cu > Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION OF HEAVY METAL ADSORPTION IN A MULTIMETAL SOLUTION BY BENTONITE-KAOLIN-ZEOLITE PELLETS

Background: Heavy metals contamination of surface and groundwater is a major environmental problem. Clay minerals are porous and are efficient to adsorb metal ions. Amongst the available treatment technologies, adsorption is the most cost-effective, easy to operate, scalable, and replicable to remediate heavy metals from water solution. Aim: This study aimed to assess the adsorption performance of clay pellets of natural aluminosilicates, bentonite (29%), kaolin (4%) and zeolite (67%) to remove heavy metals from aqueous solutions. Methods: The effect of optimal operating conditions like contact time, adsorbent dose, pH, and heavy metals initial concentration has been studied. Kinetic and equilibrium studies were also performed. Adsorbents were characterized using FTIR analysis. Results and Discussion: Optimum values for contact time, adsorbent dose, pH, and initial concentration of lead, copper, and cadmium were; 240 min; 25 g/L; 4.3; and 4mg/L, 7 mg/L and 2 mg/L, respectively. The Langmuir isotherm was the best-fitted isotherm model for the three metals. Adsorption kinetics showed that the lead and copper adsorption followed the pseudo-second-order model while cadmium suited with the pseudo-first-order model. The selectivity of the pellets towards the metal ions was in the order of Pb > Cu > Cd. Conclusions: The new combination of bentonite-kaolinite-zeolite pellets worked well in tertiary wastewater treatment and successfully utilized as a natural adsorbent in multimetal solution. The results confirmed that the used clay pellets have better adsorption capacity than many other reported studies. Maximum adsorption capacity can be further increased by adjusting the calcination temperature and applying chemical treatments to the clay pellets before extrusion. The response surface analysis evaluated the predicted optimal values for the four operating factors.

Low concentration cadmium removal using weathered sand of basalt

The natural weathered sand of basalt (WSB) has been used for the removal of cadmium from aqueous solution. The influence of various parameters i.e., contact time, pH, weathered sand of basalt dosage, particle size of the weathered sand of basalt, temperature and initial cadmium concentration were analyzed. Cadmium adsorption kinetics was well described by the pseudo second order model. Adsorption equilibrium for cadmium was properly well fitted to Langmuir isotherm model with maximum adsorption capacity 0.50 mg/g. Compared with the other experimental results using various kinds of adsorbents at a low concentration (1.0 mg/L or so) similar to that of this study, the cadmium removal efficiency using weathered sand of basalt was higher. It has been demonstrated that weathered sand of basalt has a available alternative adsorbent for cadmium when its initial concentration is low.

Effectiveness of rough horsetail plant (Equisetum hyemale) and Mexican sword plant (Echinodorus paleafolius) as a phythoremediation agent in reducing cadmium metal (Cd) in the upper Citarum River segment of Dayeuhkolot

Cadmium is one of the pollutants found in the Citarum River which is dangerous because it can accumulate in body tissues and cause toxic effects on organisms. The purpose of this research was to find the water plants that have better absorption ability as phytoremediation agents for heavy metal cadmium between Equisetum hyemale and Echinodorus paleafolius. This research was conducted at the Ciparanje Greenhouse, Faculty of Fisheries and Marine Science Padjadjaran University from October to December 2020. The parameters observed in this research were water quality (pH, temperature, dissolved oxygen), plant growth, cadmium concentration, and the survival rate of common carp seeds. The results showed that the initial cadmium concentration of 0,0082 mg/L can be reduced with Rough Horsetail to 0,0016 mg/L or 80,08%, Mexican Sword Plant can be reduced to 0,0019 mg/L or 76,42% and the combination between the two aquatic plants can reduce to 0,0005 mg/L or 93,5%.

Electrochemical preparation and characterization of polyaniline enhanced electrodes: An application for the removal of cadmium metals in industrial wastewater

In recent years, the shortage of water resources has become a serious threat to human and living creatures. Water shortages were caused by climate change, such as altered weather patterns, including droughts or floods, increased pollution, and increased human demand and overuse of water. Without the proper source of water, people encounter a lot of problems in health, hunger, education, and poverty. In this work, an electrochemical system was applied to cut the heavy metals in semiconductor processing wastewater and also was able to generate a notable volume of recovered water. Consequently, a batch system to treat each 10 L of heavily affected Cadmium ions effluent and recover 70% of those input solutions as a clean water resource was introduced. The systems are prepared with a pair of Polyaniline coated (PAC) electrodes together work under low voltage input, and yet still maintain a high removal efficiency of Cadmium at the maximum rate of 92% and produce reclaimed water over time with 5.5–6.5 L every 60 min. Parameters such as treatment temperature, initial concentration of Cadmium and other pollutants, electrolysis time, and the current efficiency of the system play a significant role during the process. The results obtained from electrode material analysis confirm the successfully preparing of the Polyaniline coated electrode and also describes its behavior under different working conditions. On the other hand, the efficiency of the treatment process is also carefully evaluated by examining the output effluent properties using Inductively Coupled Plasma (ICP) measurement, turbidity measurement, and total solid suspended (TSS) measurement.

Increase of chitosan selectivity and affinity toward the cadmium ions using xanthate functionalization: Application for cadmium removal from saline solutions

A Xanthate functionalized magnetic chitosan nanocomposite (XFMCN) was used for Cd(II) adsorption from high salinity water samples. The Xanthate functionalization was confirmed using the CHNS analysis, showing the sulfur content of 2.28 % in the composition of the nanocomposite. BET surface area of 44.79 m2 g−1 was obtained for XFMCN. The functionalization process resulted in a decrease in University of Tehran isotherm model (UT) constant from 6.73 to 1.80 × 10-3, showing an increased affinity toward cadmium adsorption. The impacts of contact time, the initial concentration of cadmium, adsorbent dosage, pH, temperature, and interfering ions such as Ca2+, Mg2+, Na+, SO₄2−, CO₃2−, NO₃− were investigated. The highest performance was at a contact time of 60 min and initial pH 7. The xanthate functionalization enhanced the selectivity of the adsorbent. Freundlich, Redlich Peterson, University of Tehran (UT), and Radke-Prausnitzi isotherm models described the equilibrium data well, confirming multilayer adsorption. The maximum equilibrium adsorption capacity was 55 mg g-1. Intraparticle diffusion and second-order models were suitable for describing the experimental data. Thermodynamics results showed an exothermic and spontaneous process. The adsorbed cadmium ion could easily be desorbed using hydrochloric acid 0.1 mol L−1. The recovery was studied up to five cycles, exhibiting a slight decrease in the adsorbent performance.

A Strategy to Revalue a Wood Waste for Simultaneous Cadmium Removal and Wastewater Disinfection

In this investigation, the possibility of wood waste (hardwoods such as oaks’ and alternatives’ staves from Balkan cooperage) revalorization for simultaneous cadmium removal and wastewater disinfection was examined. All samples were characterized in terms of their crystallinity index and crystallite size, amount of functional groups, and surface chemistry (determined by ATR-FTIR) as well as antibacterial activity. Mulberry is characterized by the lowest crystallinity index which can be ascribed to the highest crystallite size disabling crystallite denser packaging, while myrobalan plum has about 23% lower crystallite size that enables crystallite better packaging, thus resulting in a 42.4% higher crystallinity index compared to the mulberry. All oaks have a significantly higher amount of carboxyl groups compared to the alternatives (0.23-0.28 vs. 0.12-0.19 mmol/g). The adsorption experiments revealed that with increasing the initial cadmium concentration from 15 up to 55 mg/g, samples’ adsorption capacity increases by 89-220%. The equilibrium data fit well with the Langmuir isotherm model implying monolayer coverage of cadmium ions over a homogeneous wood surface. The relationship between the samples’ maximum adsorption capacities (ranged from 5.726 to 12.618 mg/g), their crystallinity index, and crystallite size was established. According to ATR-FTIR spectra, aldehyde, carboxyl, hydroxyl, and phenyl groups present on the wood waste surface are involved in Cd2+ adsorption which proceeds via the interplay of the complexation, cation- π interactions, and ion-exchange mechanisms. Mulberry and myrobalan plum showed about 89% and 80% of the total uptake capacity of cadmium within 60 min, while the equilibrium was attained after 240 min of contact time. Good compliance with pseudo-second kinetic order indicated that cadmium adsorption was mediated by chemical forces. Thermodynamic parameters revealed the spontaneous and exothermic character of cadmium ion adsorption onto mulberry and myrobalan plum. All studied samples provide maximum bacterial reduction (>99%) for E. coli and S. aureus. Wood waste from Balkan cooperage can be successfully used for simultaneous cadmium removal and wastewater disinfection.

Evaluation of fluoride and cadmium adsorption modification of corn stalk by aluminum trichloride

The aluminum-modified corn stalk biochar (AlCl3-BC) were prepared to adsorb fluoride from single ion solution and from binary mixtures with cadmium. FTIR spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and zeta potentiometry revealed that surface functional groups, crystal and physical structure of biochar were significantly improved by AlCl3 modification. The fluoride adsorption process consisted with pseudo-first order kinetics model and both Langmuir and Freundlich models well. The AlCl3-BC exhibited greater adsorption capacities than the original biochar (BC) with adsorption capacity of 81.65 mg g−1 at 35 °C. Both BC and AlCl3-BC showed higher capacities than those reported for other biochar. The fluoride adsorption capacity Qe from a binary solution of fluoride and cadmium gradually decreased as the initial cadmium concentration increased at fixed initial fluoride concentrations, while adsorption of cadmium increased. As the initial fluoride concentrations increased from 5 to 20 mg L−1, the Qe of fluoride increased as the Qe of cadmium decreased, indicating that fluoride adsorption by BC and AlCl3-BC was clearly reduced in the presence of cadmium. This research suggested that AlCl3-BC is a promising candidate material for single ion fluoride removal and could also achieve synergetic removal of fluoride and cadmium from contaminated water bodies.

Optimization of cadmium ions biosorption by fish scale from aqueous solutions using factorial design analysis and Monte Carlo simulation studies

This work investigated cadmium ions biosorption on Fish scales (FS) of Sardina pilchardus. Different relevant parameters such as initial pH in the range 2.14–7.76, initial cadmium concentration from 35 to 150 mg L−1, and biosorbent dose in the range 50–300 mg L−1, were examined. The effect of these parameters on the cadmium removal was analyzed and optimized using full factorial design methodology and the analysis of variance. The kinetics were modelized for pseudo-second order and pseudo-first order models. Results showed that the pseudo-second order kinetic gave the best fit for equilibrium data. The biosorption isotherms were investigated for Freundlich and Langmuir models. Langmuir isotherm model gave the best fit and led to a maximum biosorption capacity of Cd(II) on FS of 52.08 mg g−1. The results indicated that FS of was effective in the removal of cadmium ions. Optimum Cd(II) removal of 88.2 % was calculated for pH 3, 75 mg L−1 of Cd(II) and 250 mg L−1 of FS. Monte Carlo simulation was used as relatively greener pathway to study the biosorption behavior of Cd(II) ions onto FS. It showed that the interaction Cd(II) – hydroxyapatite was more favored than Cd(II) – collagen.

Evaluation of cadmium biosorption property of de-oiled palm kernel cake

Cadmium contamination is a global concern because of its widespread nature of polluting both biotic and abiotic components of ecosystem. Though many natural, chemical/synthetic components have been researched for remediation of cadmium, development of an eco-friendly, economic biosorbent still remains a challenge. Deoiled palm kernel cake (DOPC), a byproduct from palm-oil mills was investigated in the present study for its cadmium remediating capacity. DOPC was immobilized using sodium alginate polymer and biosorption studies were carried out using DOPC as adsorbent for removal of cadmium. Research revealed biosorption potential of DOPC and the optimum conditions for maximum biosorption of cadmium have been identified as 120 min of contact time, 150 rpm of agitation speed, pH 6 and 15 mg/L of initial cadmium concentration. Maximum percentage of adsorption was 99% by using 1.5 g/100 ml of adsorbent. The adsorption equilibrium data Biosorbent was characterized before and after adsorption by FTIR which showed the involvement of carboxyl, hydroxyl and amino-groups. Statement of novelty Cadmium pollution and the leading environmental problems is a global concern. Despite various attempts for development of different matrices for remediation of cadmium from contaminated samples, application of deoiled palm kernel cake (DOPC) as a biosorbent is not being explored. Present study provides quantitative data relating the richness of phytochemical repertoire DOPC possess, its resulting radical scavenging potential and its applications as an efficient, eco-friendly and economic alternative as a biosorbent matrix material for cadmium bio-remediation.

Study of multi-stage cadmium adsorption by riverine sediments

Most riverine sediments have the high capability to adsorb and store heavy metal ions. In the present study, the adsorption capacity of ‎the bed sediments collected from the Karaj River (Iran) were experimentally studied for cadmium ion adsorption. Multi-stage batch adsorption experiments were carried out for a constant ‎sediment concentration of 20 g/L and different initial cadmium concentrations ‎of 0.2, 0.5, 1, 10, 20, and 50 mg/L. The cadmium solutions with known concentrations were added to the bed ‎sediment with the mean diameter of 0.53 mm in five stages to characterize the capacity of the sediments to adsorb cadmium. The batch adsorption experiments were conducted as both kinetics and equilibrium. ‎‎The results showed that by adding cadmium ions to the sediment at each stage, the adsorption capacity was less than the previous stage, and for a cadmium concentration of 0.2 mg/L, the adsorption percent and the amount of adsorbed cadmium was reduced from 88 to 70% and 9 to 6.8 mg/kg, respectively. These changes decreased with increasing initial Cd concentrations. This process is useful for seasonal rivers in which a certain concentration of heavy metal pollution may occasionally flow over the bed.

Optimization of Cadmium Adsorption by Magnetic Graphene Oxide Using a Fractional Factorial Design.

Graphene materials have attracted increasing interest in water remediation. In this study, magnetic graphene oxide (MGO) was prepared through the modified Hummers method and the adsorption behaviors of cadmium were investigated. Firstly, the sorption kinetics, isotherms, as well as the effects of pH were investigated. Then, fractional factorial design (FFD) was used to optimize the effects of pH, temperature, time, initial concentration of cadmium ion and NaCl on cadmium adsorption. The results indicate that MGO could effectively remove cadmium ions from an aqueous solution and the sorption data could be described well by pseudo-second-order and Freundlich models, showing that the adsorption rate of cadmium ions on MGO is multilayer adsorption and dominated by the chemical adsorption. According to the FFD results, the maximum adsorption capacity of cadmium ions was 13.169 mg/g under the optimum condition of pH value 8, 45 °C, contact time 60 min, initial cadmium concentration of 70 mg/L and NaCl concentration of 100 mg/L. Higher levels of the pH value, temperature and initial cadmium concentration are beneficial to the adsorption process. These results are important for estimating and optimizing the removal of metal ions by MGO composite.

Cadmium removal from wastewater in a fixed-bed column system with modified-natural clinoptilolite-rich tuff

A number of treatments to municipal wastewater include advanced oxidation processes such as solar photo Fenton and solar photo-catalytic, biological treatment and the use of specific technologies when wastewater is polluted with heavy metals. Therein, the use of membranes, sorption processes with natural adsorbents and/or composites, and biosorption have proved to remove heavy metals efficiently. This investigation aimed to describe the behavior of the thiourea-modified natural clinoptilolite to remove cadmium from wastewater only filtered and wastewater with biological oxidation, in a column system, considering the properties of ion exchange and adsorption of the modified zeolitic material involving the novelty of this work. The importance of counting on feasible technologies to dispose of water is, without a doubt, a priority, particularly in areas, where average rainfall barely reaches 45 mm. Wastewater was treated in a continuous system with a thiourea-modified clinoptilolite-rich tuff. The initial concentration of cadmium in the wastewater was 2.4 mg/L, and an additional amount was added to reach a level of 31 mg/L. The breakthrough curves were obtained, and a mass balance was applied to the results, which accounted for the constant of adsorption 0.345 m3/kg, with a determination coefficient of 0.754. Finally, the capacity of the column system was evaluated for wastewater with biological oxidation. The results showed a cadmium uptake of 34.17%, which led to suggest a treatment in a two-column series.