Initial Pb Concentration Research Articles

Optimization of Pb(II) removal by a novel modified silica aerogel using Quince seed mucilage with response surface methodology

The synthesis of new environmentally friendly and biocompatible material is an exciting research field to remove various pollutants from water/wastewater samples. The main objective of this paper is the successful synthesis of an Eco-friendly and novel modified silica aerogel (NMSA) by adding a small amount of Quince seed mucilage (QSM, 0.05 wt%) to water glass precursor and an ambient pressure drying method. The prepared NMSA was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and N2 adsorption/desorption isotherms. Results showed that adding a small amount of QSM to the precursor causes the formation of relatively uniform nanoparticles with an approximate size of 20 nm. The synthesized NMSA was then used for Pb(II) removal from an aqueous solution. Pb(II) adsorption in NMSA was about 30% more than raw Silica aerogel (SA). After performing some preliminary experiments and confirming the excellent efficiency of the NMSA in Pb(II) removal, RSM (response surface methodology) study via a central composite design (CCD) optimization approach was made to study the effects of the interaction of the influencing variables on the adsorption efficiency. The maximum Pb(II)-removal efficiency of 75% was achieved for the optimized run with conditions of pH: 4, contact time: 62 min, NMSA dosage: 1.4 g/L, and initial Pb(II) concentration: 50 mg/L. The Pb(II) removal by the modified NMSA adsorbent well obeyed the Langmuir isotherm and a pseudo-second-order rate kinetics model.

Removal of Pb2+ and Cd2+ from contaminated water using novel microbial material (Scoria@UF1)

Microbial bioremediation of heavy metals contamination from water and wastewater has been adopted as a key tool to cope up with the harmful effects of metals. Literature reveals that materials adsorption methods and microbial mineralization were frequently used for the remediation of heavy metals in wastewater and shown their respective advantages and disadvantages. In order to give full play to the advantages of both materials and microbial methods and to avoid the disadvantages of the two methods, this study enriched a group of high efficiency urease bacteria (UF1) and loaded it on the surface of scoria to synthesize a novel microbial adsorbent (Scoria@UF1) to adsorb Pb2+ and Cd2+ ions in contaminated water. Microbial experiments showed that UF1 had the maximum biomass and urease activity for 24 h at 20–35 °C with initial pH value was 6–9. Moreover, UF1 could maintain normal microbial activity at initial concentration of Pb2+ and Cd2+ < 1 mmol/L. Metagenomic analysis showed that the UF1 community was mainly composed of Proteobacteria (46.81%) and Firmicutes (37.6%), and the addition of Pb2+ and Cd2+ ions decrease the community diversity of UF1 (ACE value decreased from 2316 to 2011 and 1893, respectively). The adsorption of Pb2+ and Cd2+ by Scoria@UF1 reached equilibrium in 20 h, and the adsorption process satisfied the pseudo-first-order adsorption kinetics model (R2 > 0.97). The theoretical maximum adsorption capacities of Scoria@UF1 for Pb2+ and Cd2+ were 0.078 and 0.054 mmol/g at 25 °C, respectively. The adsorption behavior of Scoria@UF1 for Pb2+ and Cd2+ was consistent with Langmuir isothermal model (R2 > 0.98) and follow the spontaneous endothermic process (ΔG0 < 0; ΔH0 > 0). Similarly, control experiment shows that the fixation of selected heavy metal ions by Scoria@UF1 includes the process of scoria adsorption and urease microbial mineralization, and the two ways have continuous and non-overlapping adsorption time periods (scoria: 0–8 h, microbe: 8–14 h). Scanning electron microscopy and elemental analysis showed that microorganisms were successfully attached to the surface of scoria before the reaction, and heavy metal elements formed irregular precipitation on the surface of scoria after the reaction. This study provides a theoretical basis for the application of Scoria@UF1 in treating Pb2+ and Cd2+ in contaminated water.

Treatment of compost as a source of organic material for bacterial consortium in the removal of sulfate and heavy metal lead (Pb) from acid mine drainage

Acid mine drainage can pollute the environment because it is acidic and contains toxic heavy metals. The purpose of this research was the application of a bacterial consortium to remove sulfate and reduce heavy metal lead (Pb) in acid mine drainage. The application was done in the bioreactor for acid mine drainage treatment that was treated with compost. Observations were made every five days and included observation of total bacterial growth using the Standard Plate Count (SPC) method, determination of sulfate content by gravimetry, determination of pH by use of pH meter, and determination of the concentration of heavy metal Pb using the AAS method. As a result, it was obtained that the treatment of non-sterile compost in acid mine drainage was able to reduce the initial heavy metal concentration of Pb of 84% and reduce the sulfate content by 72%, along with increasing pH and an increase in total bacterial growth. Meanwhile, sterile compost treatment was only able to reduce the Pb content by 63% and sulfate by 54%. This result indicates that the addition of compost is more effective than the treatment of sterile compost.

Developing a magnetic nanocomposite adsorbent based on carbon quantum dots prepared from Pomegranate peel for the removal of Pb(II) and Cd(II) ions from aqueous solution

Agriculture waste is a good choice for the production of carbon dots owing to its abundance, wide availability, eco-friendly nature. In this study a novel magnetic bioadsorbent based on carbon quantum dots (Fe3O4-PPCQDs) from Pomegranate peel (PP) was used as adsorbent to remove lead (Pb) and cadmium (Cd) from 50 mL of water and wastewater samples by magnetic solid phase extraction (MSPE). After adsorption ions with Fe3O4-PPCQDs at pH=6, the concentration of Pb(II) and Cd (II) ions were determined by flame atomic absorption spectrometry (F-AAS). The manufactured of Fe3O4-PPCQDs and GO nanostructures were structurally characterized by scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The quantum dots were optically characterized by UV–Vis spectroscopy. Batch adsorption experiment was conducted to examine the effects of pH, contact time, temperature and initial concentration of Pb(II) and Cd(II) from the water. The preconcentration factor and LOD for Cd and Pb were obtained 50, and (1.3 μg L-1; 15.5 μg L-1), respectively. The equilibrium data of ions sorption were well described by Langmuir and Freundlich model. The R2 values obtained by Langmuir model were higher. The absorption capacity of Fe3O4-PPCQDs for cadmium and lead were obtained 17.92 and 23.75 mg g-1, respectively.

Removal of Pb(II) Ion by Iron Oxide Nanoparticles Prepared by Annealing at Two Different Temperature

Transition metal ions have been extensively studied for the removal of heavy metal ions as efficient adsorbent from aqueous solution. In this work, Fe2O3 nanoparticles were synthesized by thermal decomposition route of FeSO4.4H2O at the presence of urea (1:1 molar ratio) at two different temperatures (500 °C and 600 °C) and characterized by XRD and TEM. The XRD result show that single-phase of α-Fe2O3 was prepared by increasing of calcination temperature from 500 °C to 600 °C. TEM images confirmed that the as-prepared products have a different shapes and that particle sizes are in the range of tens nanometers. The average crystallite size of pure α-Fe2O3 calculated from XRD pattern was 53.1 nm and 41 nm, respectively, depending on the method employed. In addition, Pb(II) adsorption has been studied and considered as a function of pH solution, contact time, initial Pb(II) concentration and also adsorbent dosage. The adsorption results show that the iron oxides were able to high percentage remove Pb(II) by increasing of contact time, adsorbent dosage and initial Pb(II) ion. The pH solution of 6 proved to be the most suitable for the removal of Pb(II).

Pb(II) adsorption mechanism and capability from aqueous solution using red mud modified by chitosan

Red mud modified by chitosan (RM/CS) was utilized as an adsorbent to effectively remove Pb(II) from aqueous solution. The surface area of RM/CS was found to significantly increase by more than 50% compared to that of original red mud. Different factors that affected the Pb(II) removal on this material, such as initial Pb(II) concentration, pH, and contact time, were investigated. The pseudo-first-order, pseudo-second-order, and intra-diffusion models were used to fit the experimental data to investigate the Pb(II)'s removal kinetics. The Pb(II) removal followed the intra-diffusion model. Additionally, the non-zero C value obtained from this model indicates that the removal was controlled by many different mechanisms. We also found that the interaction of Pb(II) and carbonate group on the material's surface played a primary role once the adsorption equilibrium was reached. Finally, the maximum adsorptive capacity was found to be about 209 mg/g. This obtained value is higher than those obtained for some other materials. Therefore, the present RM/CS should be a potential material for removing Pb(II) from aqueous solution.

Preparation of zeolite A by inorganic complex precursor route for efficient elimination of heavy metal cations from aqueous solutions

In the present study, zeolite A was synthesized via inorganic complex precursor as an efficient novel route by using tris(acetylacetonato)aluminum(III), [Al(C5H7O2)3], and tris(acetylacetonato)silicon(IV) chloride hydrochloride, [Si(C5H7O2)3]Cl.HCl. The physicochemical properties of the zeolite A were characterized by FT-IR, XRD, SEM/EDX, BJH, and BET techniques. The performance of the synthesized zeolite A was evaluated for the elimination of heavy metal cations (Co2+, Cu2+, Zn2+, Cr3+ and Pb2+) from aqueous solutions. The results revealed that removal efficiencies of the synthesized zeolite A toward all investigated heavy metal cations were obtained to be more than 95% and the maximum removal efficiency was observed for Pb2+. The influence of parameters such as pH, contact time and adsorbent amount was surveyed on the removal efficiency of Pb2+ by the zeolite A. The most desirable conditions for Pb2+ removal was attained at pH 6.5, the zeolite amount of 0.5 g, 400 mgL−1 initial concentration of Pb2+ and the contact time of 30 min. The adsorption process followed second- order kinetics model and the pseudo-second-order adsorption rate constant (k 2) was obtained to be 4.32 × 10−4 g mg−1min−1.

SYNTHESIS OF HYDROXYAPATITE FROM EUROPEAN SEA BASS (DICENTRARCHUS LABRAX) SCALES AND INVESTIGATION OF ITS USABILITY IN Pb(II) REMOVAL FROM WATERS

In this study, low-cost and eco-friendly hydroxyapatite (FS-HAp) particles were obtained from the raw fish scales of European Seabass (Dicentrarchus labrax), and used as adsorbent material to remove Pb(II) ions from solutions. For this purpose, experiments were carried out in the aqueous solutions prepared at different Pb(II) concentrations to determine optimum pH, adsorbent concentration, reaction time and initial Pb(II) concentration. Optimum removal conditions for Pb(II) adsorption onto FS-HAp were determined as pH 4.0, adsorbent concentration of 7.5 g/L, reaction time of 60 min, and initial Pb(II) concentration of 50 mg/L. Under these experimental conditions, the maximum Pb(II) removal was obtained as 97%. According to results of the study, hydroxyapatite obtained from fish scales was found to be highly efficient material to remove Pb(II) ions from water by adsorption method in order to reach high efficiency values when compared with many adsorbent materials.

Mineralization of lead by Phanerochaete chrysosporium microcapsules loaded with hydroxyapatite

In this study, microcapsules assembled with Phanerochaete chrysosporium (P. chrysosporium, PC) and hydroxyapatite (HAP) were successfully prepared and applied for Pb(II) immobilization in aqueous solution. The effect of different conditions on Pb(II) removal was investigated, such as pH, temperature, dosages of microcapsules and HAP, and initial concentrations of Pb(II). The removal efficiency of Pb(II) was in order of HAP+PC > HAP > PC > CK (control check) at the Pb(II) initial concentration of 100 mg L−1, which were 87.7%, 82.82%, 63.67% and 2.06%, respectively. Under HAP+PC treatment, P. chrysosporium secreted plentiful organic acids like formic, oxalic and citric acids, when the addition dose of HAP increased from 5 g L−1 to 15 g L−1, the production of formic acid increased remarkably from 32.37 g L−1 to 66.02 g L−1. After reaction, P. chrysosporium kept a good biological activity evidenced by the live/dead stain test. The characterization results indicated that the insoluble apatite could transform to soluble phosphate due to the secreted organic acids, then reacted with Pb(II) to form pyromorphite [Pb10(PO4)6Cl2] and lead phosphate hydroxide [Pb10(PO4)6(OH)2]. The overall results clearly demonstrated that combining P. chrysosporium with HAP could be used as a promising technology to accelerate lead immobilization.

HTDMA-modified bentonite clay for effective removal of Pb(II) from aqueous solution

This work studies the Pb(II) removal onto bentonite clay modified by hexadecyl trimethyl ammonium bromide (HDTMA). Characterizations of the unmodified and modified materials were performed by using XRD, SEM, TG-DSC, FT-IR, and BET surface area analyses. Factors influencing the uptake of Pb(II) from aqueous solution, such as pHsolution, ion strength, uptake time, adsorbent dosage, and initial Pb(II) concentration, were examined. The obtained results showed that bentonite clay was successfully modified by HDTMA, resulting in an increase in its surface area by about 70 %. The Pb(II) adsorption onto modified bentonite clay reached equilibrium at pH = 5.0 after 120 min. Studies within the isotherm and kinetic models demonstrated that the adsorption followed the Sips isotherm and pseudo-second-order kinetic models. The maximum monolayer adsorption capacity calculated from the Langmuir model at 30 °C was 25.8 mg/g, which is much higher than that obtained for the unmodified sample (18.9 mg/g). The FT-IR and TG-DSC analyses indicated that the formation of inner-sphere complexes plays a fundamental role in the mechanism of Pb(II) uptake onto HDTMA-bentonite clay. This mechanism of Pb(II) adsorption was further investigated, for the first time, by using the positron annihilation lifetime (PAL) and electron momentum (EMD) measurements. The PAL and EMD analyses indicated that the existence of Al and Si mono-vacancies in the HDTMA-bentonite should have essential contributions to the adsorption mechanism. In particular, we found a very interesting mechanism that the Pb(II) adsorption should occur inside the interlayer spaces of the HDTMA-bentonite.

Utilization of Banana (Musa sapientum) Peel for Removal of Pb2+ from Aqueous Solution

Biosorption is a convenient process for heavy metal remediation. In this study, banana peel was experimented to eliminate lead (Pb2+) from an aqueous solution following batch experiments. The functional groups of banana peel were identified by Fourier-transform infrared spectroscopy (FTIR). The adsorption mechanism was studied by the Langmuir and Freundlich adsorption isotherm model and determined the separation factor from the Langmuir adsorption isotherm. The adsorption of Pb2+ on dried banana peel had been studied at different adsorbent doses, pH, initial concentration of Pb, contact time, temperature, and agitation speed. After adsorption, Pb2+ was measured using atomic absorption spectroscopy (AAS). Maximum adsorption had taken place at pH 5 for adsorbent dose 45 g L-1. The optimum contact time and agitation speed was 30 minutes and 150 rpm, respectively for the initial Pb concentration of 100 ppm at 25°C. Both, Langmuir and Freundlich adsorption isotherm models shows the best fitting (r2 = 0.9978 and 0.9595) for Pb2+ adsorption. The maximum Pb2+ adsorption capacity was 2.1 mg g-1. The findings indicate that the banana peel waste could be a potential adsorbent for heavy metal removal. Moreover, the waste management problem could be solved in an eco-friendly manner by utilizing it for the eradication of Pb2+ from wastewater.

Lead metal biosorption and isotherms studies by metal-resistant Bacillus strain MRS-2 bacterium.

In this study, lead (Pb) biosorption studies in aqueous solution were performed with metal-resistant Bacillus strain MRS-2 (ATCC 55674) bacterium which was previously isolated from wastewater plant. It showed minimum inhibition concentration of 300 ppm Pb on the nutrient agar plates. Pb biosorption using MRS-2 bacteria was investigated under different parameters such as pH, temperature, biomass dosage, initial Pb concentration, contact time, and type of biomass by batch experiments. Pb concentration was analyzed through Inductively coupled plasma-optical emission spectrometry. The rate of biosorption (Q) and Pb biosorption capacity (qe ) were calculated for above mentioned parameters. It was observed that Pb precipitates by itself from the solution at pH 2 and 8 or above without bacteria and precipitation did not increase even in the presence of bacteria. The results showed that the highest biosorption rate and biosorption capacity (mg/g) were observed at pH 7, 25°C, 2-h contact time with live bacteria. The highest biosorption rate was observed at 1.5 g/L biomass dose and 5 ppm initial Pb concentration, whereas the highest Pb biosorption capacity was observed at 0.25 g/L biomass dose and 12.5 ppm initial Pb concentration. It was observed that Pb biosorption by live bacteria occurred through adsorption on cell surface. In this study, the biosorption isotherm analysis favored the Langmuir isotherm model indicating monolayer biosorption. This Bacillus strain showed higher Pb biosorption capacity than most of the previously reported Bacillus strains. In conclusion, this study indicates that the Bacillus MRS-2 strain can be used to remove Pb from industrial wastewaters in an ecofriendly approach.

A Preliminary Study of Potential Aquatic Macrophytes in Phytoremediation of Lead in The Muar River

It has been observed that phytoremediation of wastewater using the aquatic macrophytes system is a predominant method that is economical to construct, requires little maintenance, and can increase water quality. This research aims to quantify the potential of water hyacinth (WH) and water lettuce (WL) as phytoremediation agents to accumulate lead (Pb) and to determine the water quality of Muar River. Atomic Absorption Spectroscopy (AAS) was used to demonstrate Pb absorption from the water sample by plant tissue, which are the roots. WH and WL uptake rates of Pb were measured in a short-term experiment. The initial concentration of Pb in the Muar River was 0.514 mg/L. The maximum absorption efficiency of Pb was observed with WL compared to WH after ten days. Pb concentration in the Muar River remediated with WH and WL decreased to 0.104 mg/L and 0.063 mg/L, respectively. The bioconcentration factor (BCF) of WL and WH was greater than 1, indicating that both plants were good accumulators. The water was characterized by six parameters, which were Ammonia Nitrogen (AN), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), pH, and Total Suspended Solid (TSS). Our study demonstrated that water quality was significantly improved after phytoremediation by both plants. In conclusion, the study shows that water hyacinth and water lettuce can be used effectively as a phytoremediator agent to absorb Pb i.e. as a potential bio-accumulator. &nbsp

Kinetics and isotherms of lead ions removal from wastewater using modified corncob nanocomposite

A promising new eco-friendly sorbent from agricultural waste (silica/corncob nanocomposite) was successfully prepared and used for the removal of lead ions from the solution. The characterization and identification of the synthesized sorbents were investigated using different techniques. A comparative adsorption study between two sorbents was estimated to identify the best efficient sorbent. The potential of the best sorbent to remove lead ions (Pb2+) from an aqueous solution was investigated in batch experiments, where several parameters such as contact time, pH, sorbent dose, and initial concentration of Pb2+ ions were investigated. For deep information, Kinetic and isotherm models were applied for sorption. Furthermore, the column study was evaluated from silica/corncob nanocomposite for removal of Pb2+ ions and the potential ability of the synthetic nanocomposite to be regenerated and reuse was also studied. It is remarkable that with 0.3 g of silica/corncob nanocomposite, up to 95% of Pb2+ could be removed at pH = 5.5 after 60 min which is higher than corncob (77%). From the kinetics and isotherms data, the harmony of data was fitted with the pseudo-second-order kinetic model and the Langmuir isotherm model. From a single column results, it seems that silica/corncob nanocomposite has proven to be a promising material and economical for the removal of heavy metals. Moreover, the results showed that the removal efficiency for Pb2+ was more than 90% for the first two cycles, and then slightly decreased to 85%. So, the silica/corncob nanocomposite can be reused for the removal of heavy metals from wastewater for at least 3 cycles.

Performance evaluation of nanotubular halloysites from weathered pegmatites in removing heavy metals from water through novel artificial intelligence-based models and human-based optimization algorithm

The efforts of this study aimed to evaluate the feasibility of the nanotubular halloysites in weathered pegmatites (NaHWP) for removing heavy metals (i.e., Cd2+, Pb2+) from water. Furthermore, two novel intelligent models, such as teaching-learning-based optimization (TLBO)-artificial neural network (ANN), and TLBO-support vector regression (SVR), named as TLBO-ANN and TLBO-SVR models, respectively, were proposed to predict the Cd2+ and Pb2+ absorption efficiencies from water using the NaHWP absorbent. Databases used, including 53 experiments for Pb2+ absorption and 56 experiments for Cd2+ absorption from water, under the catalysis of different conditions, such as initial concentration of Pb2+ and Cd2+, solution pH, adsorbent weight, and contact time. Subsequently, the TLBO-ANN and TLBO-SVR models were developed and applied to predict the efficiencies of Cd2+ and Pb2+ absorption from water, aiming to evaluate the role as well as the effects of different conditions on the absorption efficiencies using the NaHWP absorbent. The standalone ANN and SVM models were also taken into consideration and compared with the proposed hybrid models (i.e., TLBO-ANN and TLBO-SVR). The results showed that the NaHWP detected in a Kaolin mine (Vietnam) with 70% nanotubular halloysites is a potential adsorbent for water treatment to eliminate heavy metals from water. The two novel hybrid models proposed, i.e., TLBO-ANN and TLBO-SVR, also yielded the dominant performances and accuracies in predicting the Cd2+ and Pb2+ absorption efficiencies from water, i.e., RMSE = 1.190 and 1.102, R2 = 0.951 and 0.957, VAF = 94.436 and 95.028 for the TLBO-ANN and TLBO-SVR models, respectively, in predicting the Pb2+ absorption efficiency from water; RMSE = 3.084 and 3.442, R2 = 0.971 and 0.965, VAF = 96.499 and 96.415 for the TLBO-ANN and TLBO-SVR models, respectively, in predicting the Cd2+ absorption efficiency from water. Furthermore, the validation results also demonstrated these findings in practice through 23 experiments with the accuracies of 98.3% and 98.37% for the TLBO-ANN and TLBO-SVR models, respectively, in predicting the Pb2+ absorption efficiency from water; the accuracies of 98.3% and 97.46% for the TLBO-ANN and TLBO-SVR models, respectively, in predicting the Cd2+ absorption efficiency from water. Besides, solution pH was evaluated as the most critical parameter that can be adjusted to enhance the performance of the absorption of the heavy metals in this study. By using the NaHWP absorbent and the novel proposed intelligent models developed, heavy metals can be eliminated entirely from water, providing pure water/clean freshwater without any risk of adverse health effects for the short term or long term.

Adsorption/desorption performance of Pb2+ and Cd2+ with super adsorption capacity of PASP/CMS hydrogel.

Super-absorbent polyaspartic acid/carboxymethyl Salix psammophila powder (PASP/CMS) hydrogel was prepared by aqueous solution polymerization. PASP/CMS hydrogel was characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that PASP/CMS hydrogel is prepared by graft copolymerization of the -COOH of polyaspartic acid (PASP) and the -CH2OH of CMS. The surface of the hydrogel became dense from loose porosity, and Pb2+ and Cd2+ were adsorbed onto the surface of hydrogel. The crystallinity of CMS was destroyed by the addition of PASP. The initial concentration of Pb2+ and Cd2+, pH, adsorption time and adsorption temperature on the adsorption effect were studied through experiments. Results showed that hydrogel has a good removal effect on Pb(II) and Cd(II) ions. Pseudo-second-order kinetics and Langmuir isotherm models are represented in the process, which are spontaneous, exothermic and decreased in randomness, and it is a single layer chemical adsorption. At the same time, the effect of desorption experimental parameters (HNO3 initial concentration, desorption time, and desorption temperature) on the experiment was studied and optimized.

Impacts of pyrolysis temperature on lead adsorption by cotton stalk-derived biochar and related mechanisms

Impacts of pyrolysis temperature of biochar on lead adsorption from aqueous solution and related mechanisms were investigated in this work. Biochars derived from cotton stalk were prepared under temperature from 250 to 650 ℃. The physicochemical properties and the Pb2+ adsorption capacity (Qe) of biochar were characterized. The results revealed that Qe was positively correlated (p < 0.01) with ash content, pH, C content and average pore diameter, and negatively correlated (p < 0.01) with O content, O/C ratio, (N + O)/C ratio and yield of biochar, respectively. Batch adsorption were performed using the optimal biochar sample (CS550), and the effects of ambient temperature, initial pH, biochar dose, adsorption time and initial concentration of Pb2+ on adsorption were explored. The results suggest that the pseudo-second-order model and Freundlich model fit the adsorption data well, and the maximum sorption capacity calculated by Langmuir model was 146.78 mg/g. SEM-EDS, FTIR and XRD were used to characterize the biochar before and after Pb2+ adsorption. The results indicate that there are six adsorption mechanisms participate in the adsorption process, and precipitation, ion exchange with AAEMs, Pb2+-π interactions and complexation were found to be the main adsorption mechanisms. The regeneration experiment results indicate that biochar could be reused to remove Pb2+ for at least 3 runs with a slight decrease in the adsorption capacity. The conclusion is that cotton stalk biochar is an environment-friendly adsorbent for the purification of wastewater containing heavy metals.

An optimization study for bio-removal of lead from aqueous environments by alkali modified Polyporus Squamosus

Rapidly increasing industrialization and urbanization cause serious environmental pollution. Discharge of polluting material from various industries such as smelting, mining, ore processing, and metal plating into the environment without treatment causes serious pollution and can have dangerous effects on the environmental balance. The utilization of low-cost adsorbents from biological materials as a replacement for costly traditional methods for adsorption of heavy metal pollutants from wastewater was reviewed. This study aimed to investigate the biosorption of Pb(II) ions from aqueous solutions with NaOH-modified Polyporus squamosus biosorbent and optimize the biosorption conditions. Firstly, the parameters most influencing the response of the biosorption for Pb(II) (initial Pb(II) concentration (Co), pH, temperature and biomass dose) were determined using Central Composite Design (CCD). The optimum conditions were evaluated as 60.76 mg/L, 6.3, 25 °C, and 0.23 g for Co, initial pH, temperature and biomass dose, respectively. From the optimum conditions, the adsorption yield and the adsorption capacity were obtained as 93.8% and 23.63 mg/g, respectively.

Isotherms, kinetics and thermodynamics of pb(ii) adsorption by crosslinked chitosan/sepiolite composite

A novel composite adsorbent was prepared from chitosan (Ch) and sepiolite (S) for removal of Pb(II) from aqueous solution. The Ch-S composite beads were successfully synthesized by crosslinking epichlorohydrin (ECH) and tripolyphosphate (NaTPP). A number of physicochemical parameters such as, pH, initial Pb(II) concentration, temperature, contact time and desorption have been studied during the adsorption process. Experimental data acquired from batch adsorption tests have been analyzed by three isotherm models (Langmuir, Freundlich and Dubinin–Radushkevich), and three kinetic models including the pseudo-first-order, the pseudo-second-order and intraparticle diffusion equations using nonlinear regression technique. Langmuir isotherm was the best to fit the experimental data (R2 = 0.971). The maximum adsorption capacity was 0.158 mol kg−1 from Langmuir isotherm model. Maximum removal efficiency was found approximately 66% for the initial Pb(II) concentration of 1000 mg/L, adsorbent dosage of 100 mg and agitation speed of 150 rpm at pH 4.5. The adsorption free energy was found as EDR (15.8 kJ mol−1), which indicated that Pb(II) adsorption process onto Ch-S composite was chemically performed. The kinetic studies have shown that the best fitted kinetic model is the pseudo-first order (R2 = 0.979). Adsorption enthalpy value was determined as 18.7 kJ mol−1, adsorption entropy was found as 106 J mol−1 K−1, and Gibbs free energy was found as 12.9 kJ mol−1. The thermodynamic parameters showed that the adsorption of Pb(II) on Ch-S was endothermic, possible and spontaneous.

Investigation of the transport characteristics of Pb(II) in sand-bone char columns.

Pb(II) leakage from batteries, dyes, construction materials, and gasoline threaten human health and environmental safety, and suitable adsorption materials are vitally important for Pb(II) removal. Bone char is an outstanding adsorbent material for water treatment, and the effectiveness in Pb(II) removing need to be verified. In this paper, the transport characteristics of Pb(II) in columns filled with a sand and bone char mixture were studied at the laboratory scale, and the influences of the initial concentration, column height, inlet flow rate, and competing ion Cu(II) on Pb(II) adsorption and transport were analyzed. The Thomas and Dose-Response models were used to predict the test results, and the mechanisms of Pb(II) adsorption on bone char were investigated. The results showed that the adsorption capacity of the bone char increased with increasing column height and decreased with increasing initial Pb(II) concentration, flow rate, and Cu(II) concentration. The maximum adsorption capacity reached 38.466 mg/g and the saturation rate was 95.8% at an initial Pb(II) concentration of 200 mg/L, inlet flow rate of 4 mL/min, and column height of 30 cm. In the competitive binary system, the higher the Cu(II) concentration was, the greater the decreases in the breakthrough and termination times, and the faster the decrease in the Pb(II) adsorption capacity of the bone char. The predicted results of the Dose-Response model agreed well with the experimental results and were significantly better than those of the Thomas model. The main mechanisms of Pb(II) adsorption on bone char include a surface complexation reaction and the decomposition-replacement-precipitation of calcium hydroxyapatite (CaHA). Based on selectivity, sensitivity, and cost analyses, it can be concluded that bone char is a potential adsorbent for Pb(II)-containing wastewater treatment.