Initial Metal Concentration Research Articles

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g−1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Intensification of strontium (II) ion biosorption on Sargassum sp via response surface methodology

A batch system was employed to investigate the biosorption of strontium (II) on Sargassum sp. The biosorption of strontium on Sargassum sp was studied with response surface methodology to determine the combined effect of temperature, initial metal ion concentration, biomass treatment, biosorbent dosage and pH. Under optimal conditions, the algae's biosorption capacity for strontium (initial pH 7.2, initial strontium concentration 300 mg/l for Mg-treated biomass and biosorbent dosage 0.1 g in 100 mL metal solution) was measured at 103.95 mg/g. In our analysis, equilibrium data were fitted to Langmuir and Freundlich isotherms. Results show that the best fit is provided by the Freundlich model. Biosorption dynamics analysis of the experimental data indicated that strontium (II) was absorbed into algal biomass in accordance with the pseudo-second-order kinetics model well.

Adsorptive Removal of Potentially Toxic Elements From Wastewater Using Peanut Shells Biochar

This study aimed to investigate the efficiency of the peanut shell biochar that prepared by physical activation using pyrolysis process at 550°C as a low cost adsorbent for metal ions removal from wastewater. The biochar surface morphology, chemical functional groups and the porous structure were investigated by SEM, FTIR and BET method respectively. Different parameters that affect the metal ions adsorption were taken in consideration during adsorption experiments. These parameters included pH value (3 – 8), initial metal concentration (5 – 100mg/l), biochar dose (0.5 – 4g), contact time (5 – 240 min) and temperature (25 – 60°C). The results showed that the optimum metal ions adsorption conditions were pH 6, metal concentration 20mg/l, biochar dose 2.5g, 60min of contact time and 60°C of solution temperature. The adsorbent removal efficiency for the studied metal ions exceeded 80% from the total metal concentration. The obtained results confirmed the efficiency of the biochar from peanut shell as an active adsorbent for metal ions removal from aqueous solutions.

Diallyl dimethyl ammonium chloride (DADMAC) and acrylic acid (AAc) embedded nonwoven irradiated polyethylene fabric as efficient adsorbent to separate U(VI) from aqueous solution

Selective isolation of uranium (VI) from wastewater is now a subject of concern due to its damaging effect on living beings. In this study, the pre-irradiation technique was used to prepare grafted polymeric adsorbent by diallyl dimethyl ammonium chloride (DADMAC) and acrylic acid (AAc) onto nonwoven polyethylene fabric (PE) and the grafted adsorbent was applied for uranium (VI) adsorption from aqueous solution by batch method. After irradiation of the non-woven polyethylene fabrics with 50 kGy radiation dose, the grafting reaction was carried out at 80 ºC with a monomer solution consisting of 20 g DADMAC and 20 g AAc to 110 mL deionized water. The prepared adsorbent was characterized by Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), and Thermo-gravimetric Analysis (TGA). After treatment with NaOH solution, the adsorption study was analyzed by pH, initial metal ion concentrations, contact time, and temperature on the adsorption of U(VI). The highest graft yield was achieved at 598%. The maximum adsorption capacity achieved at 160 mg/g was found by treating with 0.1M NaOH for 4 minutes with an initial concentration of 1000 ppm, pH 3.3, and a contact time of 48 hours at room temperature (25 °C). Kinetic adsorption data fitted better with the pseudo-second-order equation and a good correlation of experimental data with the Langmuir isotherm model suggested monolayer adsorption. Langmuir equation showed that the maximum adsorption capacity for U(VI) was 333.333 mg/g. The study depicted good results on the desorption and reuse of the adsorbent.

Kinetic and Equilibrium Studies on the Adsorption of Lead and Cadmium from Aqueous Solution Using Scenedesmus sp.

The current study aimed to investigate the viability and characteristics of Scenedesmus sp. as an adsorbent system to remove lead (Pb) and cadmium (Cd) through an in vitro exposure to a metal solution. In batch sorption experiments, the effects of pH, contact time, initial concentration of metal ions, and sorbent dosage on the adsorption process were trialed. The ideal biosorption conditions for each of the two metals were recorded. The biosorption process was quick, and the equilibrium times for the above-mentioned metals were recorded as 90 and 60 min, with removal percentages of 85% and 83%, respectively. The point zero charge of algal biomass was 4.5, which indicates a negative charge on the surface of the biosorbent. The model-based assessment of the biosorption process was revealed to have followed pseudo-second-order kinetics. The adsorption isotherms for lead and cadmium achieved a best fit with the Langmuir model, with monolayer biosorption capacities of 102 and 128 mg g−1, respectively. The desorption of both metals achieved more than 70% by using HCl. The FT-IR revealed the presence of hydroxyl and amine groups on the surface of the adsorbent that are involved in the biosorption process, and morphological changes were assessed by SEM. Hence, Scenedesmus sp. from a Himalayan provenance showed considerable promise as an alternate sorbent for the treatment of heavy-metal-contaminated wastewater.

Utilization of date pits derived Bio-adsorbent for heavy metals in wastewater treatment: Review

This article provides an overview of the role of raw and burnt date pits as bio-waste for heavy metal removal. In recent years, many studies on the adsorption properties of various low-cost adsorbents, such as agricultural waste and activated carbons based on agricultural waste, have been published. This review summarizes recent research demonstrating the utility of raw and modified date pits biomass-based adsorbents in the removal of heavy metal pollutants from wastewater. Additionally, the chemical compositions, the derived activated carbon, and the proposed mechanism of heavy metal ions were discussed. It thoroughly showed how essential variables including pH, adsorbent dosage, initial metal ion concentration, physical and chemical properties, and temperature affect the adsorption of heavy metals. The significant application of date pits as a bio-adsorbent of heavy metal ions was demonstrated. According to the literature, date pit-based adsorbents are the most promising adsorbents for removing toxic materials because they adsorb heavy metals from aqueous solutions with high capacity in a short period.

A Review on Removal of Heavy Metals by Biosorption: A Green Technology

Heavy metals have been introduced into the environment because of industrialization. It is well known that heavy metals linger in the environment and endanger organisms. Industrial effluents include microorganisms. To counteract the negative impacts of these metals, they have implemented a variety of measures. These tactics can depend on or be independent of metabolism. One such tactic is biosorption, which involves the interaction of metal ions with cell wall-based metal binding proteins. Algae, fungi, yeasts, and bacteria all engage in biosorption. In addition to live things, leftovers of dead microorganisms also possess biosorbent qualities, such as agricultural wastes like husks, seeds, peels, and stalks from various plants. Temperature, pH, the nature of the biosorbents, the surface area to volume ratio, the quantity of biomass, the initial metal ion concentration, and the metal affinity to the biosorbent are some of the variables that influence the rate of biosorption. Biosorption can be explained using several models, including the Freundlich model and the Langmuir model. Utilizing substances such as thiosulfate, mineral acids, and organic acids, biosorbed metals can be recovered. To avoid changing a biosorbent's physical qualities, the desorption agent should be carefully chosen. It concludes that, biosorption is an effective green technology to remove heavy metals from various types of effluents. Keywords: Heavy metals, biosorption, bacteria, algae, fungi, yeasts.

Efficiency of chemically modified activated carbon derived from banana peel for removal of Pb2+ and Zn2+ from aqueous Solution

Natural and anthropogenic activities generally result to large production of heavy metals. These heavy metals produced are indiscriminately discharged into rivers and other water bodies. Wastewater treatment of industrial effluents become very necessary due to toxic effect of heavy metal pollutants and its indirect effect pose to human health. Banana peel, an agricultural waste biomass can be used to produce bio-sorbent for adsorption of heavy metals from industrial wastewater. This study focused on the production of chemically modified activated carbon using various concentrations of phosphoric acid for removal of lead and zinc metals from aqueous solution. Activated carbon was produced from waste banana peel through thermal pretreatment at temperature of 450℃ preceding chemical modification with different concentrations of phosphoric acid of 0.5 M, 1.0 M and 1.5 M. The three different concentrations of the phosphoric acids represent sample X, Y and Z respectively. To study the adsorption efficiency of chemically modified activated carbon using different concentrations of phosphoric acid, batch experiments were conducted on chemically modified samples to assess the adsorption of lead (II) and zinc metals from aqueous solution. The three adsorbents were interacted with varying parameters such as effect of initial concentration of lead and zinc metal of concentration of 10 mg/L and 2 mg/L respectively. Based on batch experiments conducted, results indicated that adsorbent dose, pH, initial concentration as well as contact time are important factors influencing lead (II) and Zinc metals adsorption from aqueous solutions. Percentage adsorption of lead (II) and zinc metals was above 80 % for all three chemically modified adsorbents investigated. The adsorption capacities of the adsorbents under study showed high adsorption capacity for both zinc and lead metals. This implies that sample X, Y and Z are good adsorbents for adsorption of both zinc and lead metals in an aqueous solution.

Adsorption of Pb2+ and Cd2+ on the l‐cysteine‐functionalized graphene oxide/chitosan/polyvinyl alcohol hydrogel: Kinetic, isotherm, and thermodynamic study

AbstractIn this study, polyvinyl alcohol‐chitosan‐cysteine‐functionalized graphene oxide (PCCFG) hydrogel was synthesized from l‐cysteine‐functionalized graphene oxide (CFG), chitosan (CS), and polyvinyl alcohol (PVA). The hydrogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy and employed for removing lead ion (Pb2+) and cadmium ion (Cd2+) from aqueous solution. The effects of initial metal ion concentration, hydrogel dose, pH, time, and temperature were studied. The experimental data were well described by a pseudo‐second‐order kinetic model and Langmuir isotherm with maximum adsorption capacities of 250 and 192 mg g−1 at 25°C for Pb2+ and Cd2+, respectively. The adsorption capacity of the PCCFG hydrogel increased with an increase in temperature. The value of ∆G° was negative, which shows the spontaneity of the reaction (electron exchange or ion exchange) between the metal ion and electron‐rich atoms (–N, –S, –O). The positive ∆H° shows that the adsorption reaction consumes energy and the positive ∆S° shows the strong affinity of PCCFG toward the Pb2+ and Cd2+ ions. Pb2+ had better affinity and less spontaneity than Cd2+. The results show that the coexistence of Pb2+, Cd2+, and Cu2+ in the solution inhibits the adsorption capacity of PCCFG.

The use of algae to remove copper and lead from industrial wastewater

The aim of the research was to evaluate the effectiveness of the removal of Cu and Pb ions by algae. The experiments were carried out in the presence of two algal populations: a pure culture of Raphidocelis subcapitata, and a mixed chlorophyta population. The research involved a model study, experiments in the presence of wastewater from the manufacture of batteries, and the study of process kinetics. The wastewater pH was 4.0, and the initial concentrations of metal ions in the wastewater were 95.4 mg/L for Pb and 48.3 mg/L for Cu, respectively. The maximum sorption capacity of the pure Raphidocelis subcapitata culture was 14.8 mg/g d.m. for Pb, corresponding to the removal of 72% of lead, and 6.1 mg/g d.m. for Cu, corresponding to the removal of 43% of copper from the wastewater. The best ion sorption efficiency in the case of the mixed chlorophyta population was 7.0 mg/g d.m. for Pb, i.e., 61% removal of lead, and 12.8 mg/g d.m. for Cu, i.e., 69% removal of copper ions from the wastewater. The optimum duration of the process was found to be 1 hour, since the majority of biomass samples reached the maximum saturation after that time. On the basis of the obtained results (Lagergren models), it was found that the dominant mechanism of the process was chemisorption.

Mesoporous Zr-G-C3N4 Sorbent as an Exceptional Cu (II) Ion Adsorbent in Aquatic Solution: Equilibrium, Kinetics, and Mechanisms Study

A mesoporous Zr-G-C3N4 nanomaterial was synthesized by a succinct-step ultrasonication technique and used for Cu2+ ion uptake in the aqueous phase. The adsorption of Cu2+ was examined by varying the operating parameters, including the initial metal concentration, contact time, and pH value. Zr-G-C3N4 nanosorbent displays graphitic carbon nitride (g-C3N4) and ZrO2 peaks with a crystalline size of ~14 nm, as determined by XRD analysis. The Zr-G-C3N4 sorbent demonstrated a BET-specific surface area of 95.685 m2/g and a pore volume of 2.16 × 10−7 m3·g−1. Batch mode tests revealed that removing Cu (II) ions by the mesoporous Zr-G-C3N4 was pH-dependent, with maximal removal achieved at pH = 5. The adsorptive Cu2+ ion process by the mesoporous nanomaterial surface is well described by the Langmuir isotherm and pseudo-second-order kinetics model. The maximum adsorption capacity of the nanocomposite was determined to be 2.262 mol·kg−1 for a contact time of 48 min. The results confirmed that the fabricated mesoporous Zr-G-C3N4 nanomaterial is effective and regenerable for removing Cu2+ and could be a potent adsorbent of heavy metals from aqueous systems.

Biofabricated copper ferrite nanoparticles: a potential nanosorbent for the removal of Pb (II) ions from aqueous media

In the present study, we describe a facile strategy for the easy removal of the heavy metal ion, Pb (II) using biosynthesized copper ferrite (CuFe2O4) Nanoparticles (Nps) prepared via a cost-effective and eco-friendly method using Pimenta dioica leaf extract. The structural characterization was performed using UV–Visible, FT-IR, XRD, XPS, TG, SEM - EDS and TEM techniques. Various characterization techniques showed that the biosynthesized CuFe2O4 nanoparticles have spherical shape with minimum aggregation and possess a size range between 7 and 16 nm. Batch experiments were carried out to analyze the adsorption efficiency of CuFe2O4 Nps by varying different experimental conditions such as pH, adsorbent dose and initial metal ion concentration. From the atomic absorption spectroscopy results, the optimum removal efficiency (99.69%) occurred at a contact time of 90 min in the solution having pH 6 with 0.06 g of nanoadsorbent. The experimental data were analyzed using adsorption isotherm and fitted with kinetic models. In the present study, we report the the highest removal efficiency of 99.69% for Pb (II) ions with minimum experimental parameters which is greater than other similar reported studies. The novel CuFe2O4 nanosorbent synthesized in the present study is highly effective in eliminating toxic pollutants. They also possess outstanding recycling characteristics for the effective removal of Pb (II) ions from aqueous media.This cost-effective and ecofriendly strategy could be utilized for addressing the emerging water contamination.

Sorption as a pre-concentration step for metal ions recovery in multi-elemental systems

Sorption is here proposed as a promising approach for metal pre-concentration and recovery from wastewater. A study was carried out on the simultaneous sorption of Co2+, Cu2+, Ni2+ and Zn2+ on macroalgae, microalgae and cyanobacteria. The effect of pH, initial metal concentration, metal competition and time of contact on metal sorption were evaluated. Metal competition hampers sorption at the studied metal concentration ranges. The metal counterion (sulfate, chloride or acetate) did not influence metal sorption. The brown algae Sargassum sp. was the most promising sorbent (qmax = 0.66 ± 0.03 mmol·g−1), followed by the microalgae Phaeodactylum tricornutum (qmax = 0.36 ± 0.02 mmol·g−1) and the cyanobacteria Spirulina sp. (qmax = 0.216 ± 0.007 mmol·g−1). All biomass samples showed preferential sorption of Cu2+. The experimental kinetic data were well described by Ho’s model, showing chemisorption to be the main sorption mechanism. Ion-exchange of Ca2+, K+ and H+ also played a significant role in metal sorption. After sorption, metal recovery was achieved resorting to incineration. The metal content of the obtained biochar was 4639-fold higher when compared to the initial aqueous solution concentration.

Hydrological controls on base metal precipitation and zoning at the porphyry-epithermal transition constrained by numerical modeling

Ore precipitation in porphyry copper systems is generally characterized by metal zoning (Cu–Mo to Zn–Pb–Ag), which is suggested to be variably related to solubility decreases during fluid cooling, fluid-rock interactions, partitioning during fluid phase separation and mixing with external fluids. Here, we present new advances of a numerical process model by considering published constraints on the temperature- and salinity-dependent solubility of Cu, Pb and Zn in the ore fluid. We quantitatively investigate the roles of vapor-brine separation, halite saturation, initial metal contents, fluid mixing and remobilization as first-order controls of the physical hydrology on ore formation. The results show that the magmatic vapor and brine phases ascend with different residence times but as miscible fluid mixtures, with salinity increases generating metal-undersaturated bulk fluids. The release rates of magmatic fluids affect the location of the thermohaline fronts, leading to contrasting mechanisms for ore precipitation: higher rates result in halite saturation without significant metal zoning, lower rates produce zoned ore shells due to mixing with meteoric water. Varying metal contents can affect the order of the final metal precipitation sequence. Redissolution of precipitated metals results in zoned ore shell patterns in more peripheral locations and also decouples halite saturation from ore precipitation.

Optimization of Pb Adsorption from Seawater from Former Bauxite Mines Using Crab Shell Waste

Crab shell waste can cause pollution to the surrounding environment, but has the potential to be used as a biosorbent in the absorption of heavy metals, especially Pb because crab shells contain CaCO3 and chitin. Methods: Several variables that play a role in the biosorption process, among others: initial metal concentration, biosorbent mass, and contact time. Pb metal was determined by the Atomic Absorption Spectroscopy (AAS) method. Results: The results showed that the crab shell biosorbent contained Pb 0.019 mg/g. The concentration of Pb in the shell was used as a correction factor. Optimal result for parameter of initial concentration of Pb is 100 mg/L with efficiency percentage (99.11 ± 0.02)% and adsorption capacity (620.15 ± 0.3) ug/g. The optimal result of contact time is 120 minutes with efficiency percentage (91.22 ± 0.13)%. The optimal yield of biosorbent mass based on the percentage efficiency (98.01 ± 0.2)% is 2 grams. Conclusion: This study can show that crab shell waste can be used as an effective biosorbent for Pb metal adsorption. The results of the optimization of the best factors to be used in the biosorption process of Pb metal were the initial concentration of 100 mg/L, the mass of the biosorbent was 3 grams and the contact time was 110 minutes. The optimum conditions for Pb adsorption were successfully applied to seawater from the former bauxite mine.

Biosorption of Cadmium and Lead by Dry Biomass of Nostoc sp. MK-11: Kinetic and Isotherm Study

Cadmium (Cd) and lead (Pb) are global environmental pollutants. In this study, Nostoc sp. MK-11 was used as an environmentally safe, economical, and efficient biosorbent for the removal of Cd and Pb ions from synthetic aqueous solutions. Nostoc sp. MK-11 was identified on a morphological and molecular basis using light microscopic, 16S rRNA sequences and phylogenetic analysis. Batch experiments were performed to determine the most significant factors for the removal of Cd and Pb ions from the synthetic aqueous solutions using dry Nostoc sp. MK1 biomass. The results indicated that the maximum biosorption of Pb and Cd ions was found under the conditions of 1 g of dry Nostoc sp. MK-11 biomass, 100 mg/L of initial metal concentrations, and 60 min contact time at pH 4 and 5 for Pb and Cd, respectively. Dry Nostoc sp. MK-11 biomass samples before and after biosorption were characterized using FTIR and SEM. A kinetic study showed that a pseudo second order kinetic model was well fitted rather than the pseudo first order. Three isotherm models Freundlich, Langmuir, and Temkin were used to explain the biosorption isotherms of metal ions by Nostoc sp. MK-11 dry biomass. Langmuir isotherm, which explains the existence of monolayer adsorption, fitted well to the biosorption process. Considering the Langmuir isotherm model, the maximum biosorption capacity (qmax) of Nostoc sp. MK-11 dry biomass was calculated as 75.757 and 83.963 mg g-1 for Cd and Pb, respectively, which showed agreement with the obtained experimental values. Desorption investigations were carried out to evaluate the reusability of the biomass and the recovery of the metal ions. It was found that the desorption of Cd and Pb was above 90%. The dry biomass of Nostoc sp. MK-11 was proven to be efficient and cost-effective for removing Cd and especially Pb metal ions from the aqueous solutions, and the process is eco-friendly, feasible, and reliable.

Valorization of Groundnut Shell Biomass for Biosorption of Hexavalent Chromium from Aqueous Solution

Biosorption is a cost-effective biotechnological innovation for the removal of heavy metals from aqueous solutions. There is widespread research into ways of utilizing agricultural residues to achieve zero waste. Groundnut shells are biodegradable waste available in large quantities. This study investigated the use of groundnut shells for the biosorption of chromium (VI) ions from an aqueous solution. Groundnut shells were cleaned and crushed to make fractions of particle size in the range of 90-1000 µm. The point of zero charge (pHPZC) and the distribution of oxygenated acidic and basic surface functional groups were determined. In batch experiments, the effect of acid pre-treatment, initial metal concentration, biosorbent particle size, biosorbent dosage, and contact time on biosorption was investigated. The biomass was found to have a pHPZC value of 6 and was dominated by acidic groups. The best biosorption activity was observed at 20 mg/L initial metal concentration and a biosorbent dosage of 10%. The effect of contact time was dependent on the initial chromium (VI) concentration. At 20 mg/L initial chromium (VI) concentration, the biosorption process reached equilibrium within 60 minutes whilst at high (>80 mg) chromium (VI) concentration equilibrium was not reached, even after 240 minutes. The best biosorption activity was observed with acid-treated biomass of particle size 300 µm. The adsorption fitted best with the Langmuir isotherm model and the pseudo-second-order kinetic model (R2 > 0.9982). Groundnut shell biomass has the potential for the removal of chromium (VI) ions from aqueous solutions and possibly from chromium-polluted effluents on an industrial scale.

REMOVAL OF HEAVY METALS BY ADSORBENT PRODUCED FROM KHAYA SENEGALENSIS

Mankind quest for better life has led to advancements in modern technologies which include a number of manufacturing processes and methodologies. Some of these processes and methodologies often release harmful substances into the environment including heavy metals which lead to pollution. These heavy metals are non-biodegradable and therefore need to be removed. Attention has been devoted to emerging technologies which are relatively cheap, for the removal of heavy metal ions from contaminated waters. Adsorption of heavy metal ions using biological materials is one such technologies. As such, the adsorption of Cr(vi), Cd (ii), Zn (ii) and Ni(ii) from synthetic solution by activated carbon from Khaya senegalensis was studied in a batch experiment as a function of pH, metal concentration, adsorbent dose and contact time. Solutions after the batch experiments were analyzed using atomic absorption spectrophotometer. The result revealed dependency of adsorption process on pH. The optimal metal removal occurred at pH 6 for Cd (ii), Zn (ii) and Ni (ii) and 3 for Cr (vi). Maximum adsorption of 82.2 %, 78.9 %, 87.2 % and 83.3 % was attained for Cr (vi), Cd (ii), Zn (ii) and Ni (ii) respectively. Adsorption capacity of the adsorbent improved with initial metal concentration. Ion exchange seemed to be the major mechanism of adsorption in this study. The data collected was were modelled by the Langmuir isotherm over the entire concentration range, suggesting a monolayer coverage. The result showed that, sulphurised Khaya senegalensis is effective in removing heavy metal ions from aqueous solution.

On the adsorption of neodymium species from aqueous solution by beneficiated palygorskite

Run-of-mine (ROM) palygorskite (PAL) from Guadalupes (Piauí/Brazil) was prepared, beneficiated and then properly characterized by physical–chemical analyses. Then, the removal of Nd3+ ions by PAL was evaluated as a function of solution pH, adsorbent concentration, and initial metal concentration. The results showed that the maximum sorption capacity was 18 mg/g, and more than 99 % of Nd was remove from the solution at pH 5. The sorption data were analysed by several isotherm models, but the better good of fitness (R2 ≥ 0.97; RMSE ≤ 0.98) was attributed to the Temkin model. It́s suggested that the adsorption process proceeds firstly by the introduction of the Nd ions into the interior and exterior pore of PAL, then the PAL surface acquires a negative charge by deprotonation of PAL actives sites (Me-OH), and then the capture of the Nd3+ ions on its inside and outside surface may take place through electrostatic interaction. Thermodynamic parameters indicated that the sorption process was favourable and endothermic. Thus, the present results pointed out that palygorskite has potential for removing Nd ions, and probable another rare earth elements from aqueous solutions, being a promisor adsorbent to the treatment of effluents containing neodymium, e.g. industry of permanent magnets.

Using Chemically Unprocessed Orange Peel to Effectively Remove Hg(II) Ions From Aqueous Solutions: Equivalent, Thermodynamic, And Kinetic Investigations

This study looks at the capacity of raw orange peel (ROP) to adsorb Hg2+ ions from aqueous solutions. According to the results obtained, it is aimed at using ROPs more efficiently by recycling them. In this way, the usability of both ROP and other agricultural wastes in adsorption processes can be investigated. The effects of many variables on adsorption efficiency were investigated in the study, including initial metal ion concentration (MIC), contact time (CT), and pH. Under optimal operating conditions for Hg2+ ion adsorption, CT, solution pH, and initial concentration were determined to be 90 minutes, 3.08, and 180 mg/L, respectively. SEM, Fourier transform infrared spectroscopy (FT-IR), energy dispersion spectroscopy, and Brunauer, Emmett, and Teller (BET) analyses were used to examine the surface features of ROP. The isotherm values were found to be appropriate for the Langmuir isotherm model, indicating chemical absorption and likely process irreversibility. At 318, 308, and 298 K, the capacity of adsorption for the Hg2+ ion was calculated to be 66.225, 63.291 and 61.728 mg/g, respectively. The pseudo-second order (PSO), which exhibited the largest regression coefficient and best described the kinetic data for the removal of Hg2+ ions, according to thermodynamic studies, it was seen that the adsorption of Hg2+ ions on ROP is a natural and endothermic process. ROP, which is abundant throughout the world, can be used effectively in its natural state without any modification or chemical treatment, together with Hg2+ adsorption, to remove other heavy metals, dyestuffs, and toxic substances. ROP has been recognized as a potent and promising material for eliminating Hg2+ ions from the aquatic environment due to its characteristics such as high adsorption capability, cheap cost, and ease of availability.