Adsorption Of Pb Research Articles

Adsorptive removal of Pb(II) ions from aqueous effluents using O-carboxymethyl chitosan Schiff base-sugarcane bagasse microbeads

In this study, a novel and cost-effective approach was employed to prepare an effective Pb(II) adsorbent. We synthesized highly porous CMCSB-SCB microbeads with multiple active binding sites by combining carboxymethylated chitosan Schiff base (CMCSB) and sugarcane bagasse (SCB). These microbeads were structurally and morphologically characterized using various physical, analytical, and microscopic techniques. The SEM image and N2-adsorption analysis of CMCSB-SCB revealed a highly porous structure with irregularly shaped voids and interconnected pores. The CMCSB-SCB microbeads demonstrated an impressive aqueous Pb(II) adsorption capacity, reaching a maximum of 318.21 mg/g, under identified optimal conditions: pH 4.5, 15 mg microbeads dosage, 30 min contact time, and Pb(II) initial concentration (350 mg/L). The successful adsorption of Pb(II) onto CMCSB-SCB beads was validated using FTIR, EDX, and XPS techniques. Furthermore, the experimental data fitting indicated a good agreement with the Langmuir model (R2 = 0.99633), whereas the adsorption kinetics aligned well with the pseudo-second-order model (R2 = 0.99978). The study also identified the Pb(II) adsorption mechanism by CMCSB-SCB microbeads as monolayer chemisorption.

Montmorillonite Clay as an Adsorbent for the Remediation of Cd (II) Ions in Aqueous Solutions: A Comparison With Pb (II) Ions

ABSTRACTHeavy metal ions are hazardous to both human health and the environment. Montmorillonite (MMT) clay has recently piqued interest for its adsorption capacity of heavy metals and its use in controlling contaminants, in particular in surface and waste waters. This research sheds light on the possibility of the application of natural Albanian MMT clay from the Prrenjas Region of Albania as an adsorbent of Cd (II) ions in aqueous solutions, making a comparison with the capacity of such clay for the adsorption of Pb (II) ions. The set of variables studied included concentrations of metal ions, amount of clay pH, time, and temperature of interaction and adsorption process (all of them following batch technique), and optimal conditions have been determined. The adsorption capacity of natural clay for Cd (II) ions was 6.735 mg/g, as compared to 17.9 mg/g for Pb (II) ions. Langmuir and Freundlich isotherms were applied to evaluate the mode of adsorption with results showing that all isotherms are linear and the Langmuir model fitted better with the experimental data. It is determined that the adsorption of Cd (II), similar to that of Pb (II), is well‐fitted by the second‐order reaction kinetic following the Lagergen model. The results demonstrate good potentiality for Prrenjas MMT as a low‐cost adsorbent to remove Cd (II) from aqueous systems, in particular, for wastewater treatment.

Adsorption of Pb2+ ions of natural red lava rock powder in aqueous media

Red lava rock is available in nature and is formed from volcanic eruptions. Volcanic rocks are composed of oxides of diverse metals and have considerable porosity. In this study, lava rock powder was ground to a specific size and dried to test its ability to adsorb heavy metals in water. The morphology of the stone powder was observed to show crystals of 100–300 nm in size clumping into particles of a few μm. The phase structure is mainly in the form of Ca(Mg,Al)(Si,Al)2O6; in addition, the phases CaAl2Si4O12.2H2O, Ca2MgSi2O7, and Ca3MgSi2O8 also exist. The material's maximum Pb2+ ion adsorption capacity reaches 32.05 mg/g at endogenous pH. The isotherm of Pb2+ adsorption on the material follows the Langmuir model, and the adsorption kinetics are pseudo-first-order kinetics.

Enhanced Adsorption of Aqueous Pb(II) by Acidic Group-Modified Biochar Derived from Peanut Shells

Using peanut shells, a sustainable agricultural waste product, as its raw material, the acid group-modified biochar (AMBC) was prepared through phosphoric acid activation, partial carbonization, and concentrated sulfuric acid sulfonation for efficient removal of lead ion from aqueous solutions. Characterization techniques such as N2 isothermal adsorption–desorption, SEM, XRD, FT-IR, TG-DTA, and acid–base titration were utilized to fully understand the properties of the AMBC. It was found that there were high densities of acidic oxygen-containing functional groups (-SO3H, -COOH, Ph-OH) on the surface of the AMBC. The optimal adsorption performance of the AMBC for Pb(II) in water occurred when the initial concentration of Pb(II) was 100 mg/L, the pH was 5, the dosage of the adsorbent was 0.5 g/L, and the contact time was 120 min. Under the optimal conditions, the removal ratio of Pb(II) was 76.0%, with an adsorption capacity of 148.6 mg/g. This performance far surpassed that of its activated carbon precursor, which achieved a removal ratio of 39.7% and an adsorption capacity of 83.1 mg/g. The superior adsorption performance of AMBC can be caused by the high content of acidic oxygen-containing functional groups on its surface. These functional groups facilitate the strong binding between AMBC and Pb(II), enabling effective removal from water solutions.

Pb/As simultaneous removal from soil leachate of Pb/Zn smelting sites by magnetic biochar

Lead (Pb) and arsenic (As) contaminated soils, caused by Pb and zinc (Zn) smelting activities, pose an urgent environmental issue. Magnetic biochar (MB) has been regarded as an increasingly appealing candidate for the remediation of multi-metals in contaminated soils or their leachate. Finding economically feasible preparation methods for MB and demonstrating its remediation potential is desperately required for the remediation of such complex smelting sites. In this study, a modified MB was prepared using an optimized co-precipitation method, and its application potential for Pb/As simultaneous removal based on the basic properties of a typical Pb/Zn smelting site was evaluated. The surface modifications of MB facilitated the encapsulation of various ultrafine iron oxide particles, predominantly γ-Fe2O3 and Fe3O4, whilst notably enhancing the presence of oxygen-containing surface functional groups. The adsorption of Pb(II) and As(III) by MB was well-described using the pseudo-second-order adsorption and Langmuir models. The existence of SO42− and Ca2+ in the soil leachate competed with the adsorption sites for Pb(II) and As(III). Notably, within the pH range of 5–9, the adsorption efficiency of Pb(II) by MB increased with the rising solution pH, whereas alterations in pH minimally affected the removal rate of As(III), maintaining a consistent removal rate exceeding 95%. Furthermore, dissolved organic matter (DOM) abundant in organic functional groups, particularly CO and CC groups, significantly augmented the adsorption affinity for both Pb(II) and As(III). An application rate of 2 g/L could effectively reduce the concentration of Pb(II) and As(III) in soil leachate to <0.05 mg/L. The findings demonstrated the potential of the prepared MB for simultaneous removal of As(III) and Pb(II) in soil leachate, which should be beneficial to multi-metals polluted soil remediation in Pb/Zn smelting sites.

Two-step recovery of Pb(II) and Cd(II) with thiophene functionalized hydrogel from lead-acid battery wastewater: Insight into pH-regulated separation

Lead-acid batteries (LAB) are one of the most harmful batteries to the environment and human health. LAB wastewater contains Pb(II) and Cd(II), meanwhile, strongly acidic media (pH ≤ 3.0) poses a serious threat to ecological safety and human health. Herein, a novel thiophene functionalized biomass-based hydrogel (PEITC-SA) containing various groups was prepared by a two-step synthesis strategy involving liquid-phase modification and dopant-induced crosslinking. The static experiments relating to selectivity, kinetics and equilibria confirmed that PEITC-SA not only had a high adsorption capacity and selectivity for Pb(II) at pH 2.0, but also had a good adaptability for both Pb(II) and Cd(II) at pH 3.0. Moreover, the coexistence of inorganic salts and organic compounds had little effect on the adsorption of Pb(II) and Cd(II). Complexation was confirmed as the main adsorption force at pH 2.0, meanwhile at pH 3.0, electrostatic interaction, ion exchange interaction and complexation were all involved. According to Density Functional Theory calculations, tetradentate coordination of thiophene and amino groups was the most stable. Dynamic column experiments towards simulated LAB wastewater demonstrated the high efficiency and feasibility of pH-regulated fractional treatment, which of unexpected economic prospects. Furthermore, PEITC-SA could be easily desorbed with dilute HCl solution. Therefore, PEITC-SA possessed satisfactory potential for the resource recovery towards LAB wastewater through pH-regulated two-step separation.

Acetate anions intercalated Fe/Mg-layered double hydroxides modified biochar for efficient adsorption of anionic and cationic heavy metal ions from polluted water

The simultaneous removal of anionic and cationic heavy metals presents a challenge for adsorbents. In this study, acetate (Ac-) was utilized as the intercalating anion for layered double hydroxide (LDH) to prepare a novel biochar composite adsorbent (Ac-LB) designed for the adsorption of Pb(II), Cu(II), and As(V). By utilizing Ac- as the intercalating anion, the interlayer space of the LDH was enlarged from 0.803 nm to 0.869 nm, exposing more adsorption sites for the LDH and enhancing the affinity for heavy metals. The results of the adsorption experiments showed that the adsorption effect of Ac-LB on heavy metals was significantly improved compared to the original FeMg-LDH modified biochar composites (LB), and the maximum adsorption capacity of Pb(II), Cu(II), and As(V) were 402.70, 68.50, and 21.68 mg/g, respectively. Wastewater simulation tests further confirmed the promising application of Ac-LB for heavy metal adsorption. The analysis of the adsorption mechanism revealed that surface complexation, electrostatic adsorption, and chemical deposition were the main mechanisms of action between heavy metals (Pb(II) and Cu(II)) and Ac-LB. Additionally, Cu(II) ions underwent a homogeneous substitution reaction with Ac-LB. The adsorption process of As(V) by Ac-LB mainly relied on complexation and ion-exchange reactions. Lastly, the modification of the LDH structure by Ac− as an intercalating anion, thereby increasing the affinity for heavy metals, was further illustrated using density-functional theory (DFT) calculations.

Optimization of zeolite ETS-10 synthesis for enhanced Pb(II) adsorption from aqueous solutions

The synthesis of zeolite ETS-10 is strongly influenced by factors such as pH, the amount of the structure-directing agent, hydrothermal temperature and duration, which collectively affect the material’s morphology and structure. This study thoroughly investigates the effects of these parameters on the synthesis of ETS-10 zeolite using TiCl3 and a waterglass solution. Characterization of the materials was performed through X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and nitrogen isotherm adsorption-desorption at 77 K (BET-BJH) techniques. The findings indicate that pH and the structure-directing agent significantly influenced the phase composition, while hydrothermal temperature predominantly determined the crystallization rate of ETS-10. Optimal synthesis conditions were established at an initial pH of 11, employing 0.3 g of the structure-directing agent and conducting hydrothermal crystallization at 230 °C for 24 h. Under these conditions, the ETS-10 zeolite produced exhibited a high surface area of 300.1 m2/g, making it effective in removing Pb2+ ions from solution. In particular, when tested under optimal conditions (pH 5) for 600 min, Pb (II) adsorption by ETS-10 reached a maximum uptake capacity of 956.19 mg/g, as determined by the Langmuir isotherm model. This capacity surpasses that of as-synthesized ETS-10 prepared from alternative Ti sources and other materials used in previous studies on Pb(II) adsorption.

Characterization of phosphate modified red mud-based composite materials and study on heavy metal adsorption.

In this paper, Bayer red mud (RM) and lotus leaf powder (LL) were used as the main materials, and KH2PO4 was added to modify the material. Under the condition of high-temperature carbonization, RMLL was prepared and phosphate modified red mud matrix composite (PRMLL) was prepared based on KH2PO4 modification, which can effectively remove Pb2+ from water. The optimum preparation and application conditions were determined through orthogonal experiment: dosage 0.1g, ratio 1:1, and temperature 600 °C. The effects of pH, dosage, and initial concentration on the adsorption of Pb2+ were studied. The pseudo-first-order, pseudo-second-order, and Elovich kinetic models were fitted to the experimental data. It was found that RMLL and PRMLL were more consistent with the pseudo-second-order kinetic model and chemisorption. Langmuir, Freundlich, Timkin, and Dubinin-Radushkevich isothermal adsorption models were used to fit the experimental data. It was found that RMLL and PRMLL were more consistent with Langmuir model. In addition, the maximum adsorption capacity of RMLL and PRMLL was 188.1 mg/g and 213.4 mg/g, respectively. It is larger than the adsorption capacity of their monomers. Therefore, the use of RMLL and PRMLL as the removal of Pb2+ from water is a potential application material.

Pb(II) Adsorption Properties of a Three-Dimensional Porous Bacterial Cellulose/Graphene Oxide Composite Hydrogel Subjected to Ultrasonic Treatment.

A three-dimensional porous bacterial cellulose/graphene oxide (BC/GO) composite hydrogel (BC/GO) was synthesized with multi-layer graphene oxide (GO) as the modifier and bacterial cellulose as the skeleton via an ultrasonic shaking process to absorb lead ions effectively. The characteristics of BC/GO were investigated through TEM, SEM, FT-IR, NMR and Zeta potential experiments. Compared to bacterial cellulose, the ultrasonic method and the carboxyl groups stemming from GO helped to enhance the availability of O(3)H of BC, in addition to the looser three-dimensional structure and enriched oxygen-containing groups, leading to a significantly higher adsorption capacity for Pb(II). In this paper, the adsorption behavior of BC/GO is influenced by the GO concentration, adsorption time, and initial concentration. The highest adsorption capacity for Pb(II) on BC/GO found in this study was 224.5 mg/g. The findings implied that the pseudo-second-order model explained the BC/GO adsorption dynamics and that the data of its adsorption isotherm fit the Freundlich model. Because of the looser three-dimensional structure, the complexation of carboxyl groups, and the enhanced availability of O(3)H, bacterial cellulose exhibited a much better adsorption capacity.

Functionalized graphitic carbon nitride as adsorbent for the removal of arsenic and lead from groundwater

Water pollution caused by highly toxic arsenic (As) and lead (Pb) poses a serious threat to water quality. Hence, the development of materials for their effective removal from water continues to attract research attention. The present study reports functionalized graphitic carbon nitride nanosheets (GCN) as a green and low-cost adsorbent for the removal of As and Pb from polluted water. The adsorbent was prepared through the protonation and hydroxyl and cyano functionalized graphitic carbon nitride to form H/GCN and OH/CN-GCN respectively. Characterization techniques including Fourier transform infrared (FTIR), X-ray diffraction, and scanning electron microscopy were respectively used to study functional groups, structure, and morphology of the adsorbents. The adsorption study showed that modification of GCN with −OH and CN− ions in OH/CN-GCN, increased the density of negative charges on the functionalized surface, which also enhances the attraction of the positively charged ions. This may be responsible for the improved removal of As and Pb from wastewater compared to H/GCN. Isotherm studies on the adsorption behavior of OH/CN-GCN suggest that Langmuir isotherm model corroborates with the As adsorption. Therefore, indicating that the removal of As via its adsorption onto OH/CN-GCN is a surface phenomenon. However, the adsorption of Pb could be described as mainly a multilayer adsorption process, based on its R2 value. It is proposed that the −OH and CN− groups on the tri-s-triazine units of GCN nanosheets may be responsible for the adsorption process. The prepared materials are promising adsorbents that nay find useful applications in wastewater treatment plants involving advanced oxidation processes.

Kaolin–Fly Ash Composite for Pb2+ and AsO43− Adsorption from Aqueous System

The expected benefit of composite adsorbents generally consists in their growing applicability, thanks to the combination of the adsorption properties of individual components. Composite adsorbents were prepared as mixtures of kaolin from a Czech deposit (kaolin Sedlec, SK) and two fly ashes (FAs) from a fluidised bed boiler in Czech operations differing in fuel type. The mixtures of SK with FA in a ratio of 50:50% wt. were prepared at 20 °C, 65 °C, and 110 °C in an autoclave. The source materials and composite adsorbents were tested for the adsorption of lead as Pb2+, and arsenic as AsO43− from model solutions in laboratory conditions. The adsorption of Pb2+ proceeded quantitatively on the source materials except SK, and on both the composites, with an adsorption yield of &gt;97% and a low adsorbent consumption (~2 g.L−1). The AsO43− adsorption proceeded selectively only on both FAs, with an adsorption yield of &gt;97% again. The adsorption of AsO43− on the composite adsorbents achieved a worse yield (˂80%), with about ten times more adsorbent consumption (~20 g.L−1). An increased preparation temperature did not affect the Pb2+ adsorption at all, but it reduced the efficiency of AsO43− adsorption by up to 30%. The SK–FA composites proved to have promising properties, mostly as cation-active adsorbents.

Sustainable Solutions for Heavy Metal Contamination: Characterization and Regeneration of Water Hyacinth Biosorbent in Wastewater Treatment

&lt;p&gt;The water hyacinth biosorbent has undergone thorough characterization and assessment for its capacity to remove heavy metals, specifically Pb(II) and Hg(II), from aqueous solutions. Notably, the biosorbent demonstrated an impressive maximum adsorption capacity for Pb and Hg, reaching values of 158.7 mg/g and 123.5 mg/g, respectively. Indeed, these adsorption capacities align with or even surpass those documented in the existing literature for various biosorbents derived from similar agro-industrial waste materials. Several methods were used to characterize the water hyacinth biosorbent's structure and morphology, including pH-Zero Point Change, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), and infrared spectrometry with Fourier transform (FT-IR). The water hyacinth biosorbent was found to have broken exteriors with mixed particles that involved useful adsorption clusters such as OH, C=O, and C-O-C. The most effective adsorption of Pb(II) and Hg(II) takes place at a pH of 5.0, using a hyacinth dose of 2 g/L. The chemisorption process is the primary cause of the fast growth rate of the adsorption process, which is governed by pseudo-second-order kinetics. Using a 0.1M HNO3 eluent, both biosorbents were effectively regenerated, enabling effective reuse for up to five cycles. The thermodynamic studies confirm the endothermic nature of the adsorption process.&lt;/p&gt;

Comparison the adsorption of Pb with Ecofriendly Bio-Adsorbent From Rice Husk Ash and Boiler Fly Ash

The amount of environmental pollution is in line with the increasing of industry. Industry can generate waste in the form of solid, liquid or gas. Utilization of waste as an adsorbent is a solution that can be done in dealing with waste such as metal waste contained in water. Therefore, this research aims to make a bio-adsorbent in the form of silica from rice husk ash and boiler fly ash and know the comparison of the Pb absorbed. The research method used is an experimental method by synthesizing the manufacture of silica. Then testing of Pb based on contact time was 30 minutes, 60 minutes, 90 minutes and 120 minutes. The results showed that the two silica-based bio-adsorbents could adsorb Pb. Bio-adsorbent from rice husk ash absorbed 56.51% of Pb in 30 minutes, 52.93% in 60 minutes, 48.65% in 90 minutes and 43.55% in 120 minutes. The bio-adsorbent from the fly ash boiler absorbed 50.15% of Pb in 30 minutes, 44.28% in 60 minutes, 38.48% in 90 minutes and 36.45% in 120 minutes. Bio-adsorbent from rice husk ash absorbs more Pb ions than from boiler fly ash. Because the silica in the rice husk ash forms a collection in the pores, whereas in the fly ash boiler there is silica that is spread out. This research can be a basis for further research in the form of dye bio-adsorbent products based on their short use time.

Recent Progress on the Adsorption of Heavy Metal Ions Pb(II) and Cu(II) from Wastewater.

With the processes of industrialization and urbanization, heavy metal ion pollution has become a thorny problem in water systems. Among the various technologies developed for the removal of heavy metal ions, the adsorption method is widely studied by researchers and various nanomaterials with good adsorption performances have been prepared during the past decades. In this paper, a variety of novel nanomaterials with excellent adsorption performances for Pb(II) and Cu(II) reported in recent years are reviewed, such as carbon-based materials, clay mineral materials, zero-valent iron and their derivatives, MOFs, nanocomposites, etc. The novel nanomaterials with extremely high adsorption capacity, selectivity and particular nanostructures are summarized and introduced, along with their advantages and disadvantages. And, some future research priorities for the treatment of wastewater are also prospected.

Competitive Adsorption of Aqueous Cd(II) and Pb(II) Solutions onto Silicas Synthesized with Saponin as Template Agent

The aim of the research was to prepare silica adsorbents using an environmentally friendly pathway, a template synthesis with saponin biosurfactant as a structure-directing agent. The adsorbents prepared in this way exhibit improved adsorption properties while maintaining environmental innocuousness. For the preparation of porous silica, the biosurfactant template sol–gel method was used with tetraethoxysilane as a silica precursor. The silica adsorbents were analyzed by FTIR spectroscopy, nitrogen adsorption–desorption and SEM/EDX microscopy, TEM/HRTEM microscopy, and thermogravimetric analyses. Batch tests were carried out to remediate Pb(II)/Cd(II) ions in single/binary aqueous solutions, and the effect of the surfactant on the adsorption properties was assessed. The optimal adsorption parameters (pH, contact time, initial concentration of metal ions) have been determined. The adsorption was fitted using Langmuir and Freundlich adsorption isotherms and kinetic models. Mathematical modeling of the retention process of Pb(II) and Cd(II) ions from binary solutions indicated a competitive effect of each of the two adsorbed metal ions. The experimental results demonstrated that saponin has the effect of modifying the silica structure through the formation of pores, which are involved in the retention of metal ions from aqueous solutions and wastewater.

The removal mechanism of lead from wastewater on pharmaceutical sludge-based biochar

This study aims to enhance the resource utilization of waste sludge and mitigate the environmental risks associated with Pb2+ contamination. Municipal sludge biochar (MBC) and pharmaceutical sludge biochar (PBC) were selected as the experimental subjects. The experiment systematically investigated the influential factors affecting adsorption, including adsorbent dosage, reaction time, and pH. The physicochemical attributes of the biochar (BC) were assessed through techniques such as scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and point of zero charge analysis. The Pb2+ adsorption process was described by the pseudo-second-order kinetic model and Freundlich isotherm model, the highest adsorption capacities were established as 18.56 mg/g and 19.07 mg/g for MBC and PBC, respectively. The adsorption of Pb2+ on BCs is related to chemical and physical adsorption mechanisms. Ligand bonding, monolayer chemisorption, electrostatic interactions and pore filling were considered as possible mechanisms involved in the adsorption system. It was shown that MBC and PBC are efficient adsorbents for the Pb2+ removal in water.

Characterization and decontamination evaluation of carbon composites synthesized via Co(II)-Assisted pyrolysis of phenanthroline, phenylenediamine, and melamine

The application of carbon composite materials (CCMs) spans across various fields, and their preparation primarily involves the non-oxygen pyrolysis of non-volatile macromolecular precursors, which poses challenges in tailoring their composition and microstructure. Here, we propose a binary co-pyrolysis approach for the synthesis of CCMs, utilizing small organic molecules such as Phenanthroline (Phen), o-Phenylenediamine (oPD), and Melamine (Mel) as precursors, along with Co(II) salt as a catalyst. We conducted a thermogravimetric analysis of these three binary systems, aiming to synthesize CCMs at moderate temperatures (330 − 460 °C). Subsequently, we characterized the CCMs in terms of their bulk structure, composition, and surface properties. Finally, we assessed their decontamination performance through catalytic H2O2 degradation of methylene blue and adsorption of Pb(II)/phosphate. The results revealed that Co(II) can promote the preferential formation of thermally stable intermediate polymeric structures and inhibit the direct evaporation of the precursors. The prepared CCM-Phen-Co, CCM-oPD-Co, and CCM-Mel-Co exhibit a lamellar and (N, O, Co)–co-doped amorphous structure. Furthermore, both CCM-Phen-Co and CCM-oPD-Co demonstrate complete removal efficiency for methylene blue at a concentration of 10 mg/L, while the maximum adsorption capacity of CCM-oPD-Co for Pb(II) and CCM-Phen-Co for phosphate are 58.0 mg/g and 13.6 mg/g respectively. The CCMs demonstrate promising efficacy in environmental catalysis and adsorption for decontamination purposes.

Facile and economic preparation of graphene hydrothermal nanocomposite from sunflower waste: Kinetics, isotherms and thermodynamics for Cd(II) and Pb(II) removal from water

Keeping the need for good water quality and the demand of climatic issues, the sunflower waste was converted into graphene hydrothermal nanocomposite absorbents for the removal of toxic Cd(II) and Pb(II) metal ions from water. The graphene composite materials were studied by scanning (SEM) and transmission electron microscopy (TEM), XRD analysis, TG and DSC, Raman and IR spectroscopy. According to SEM and TEM analysis, the decarbonized materials had a disordered structure with amorphous carbon with a small pore content. During the carbonization process, the pores space was opened due to the removal of amorphous organic matter and the formation of defects; providing a significant number of meso- and micropores. The prepared graphene composite showed 133.33 and 222.22 mg/g Langmuir adsorption of Cd(II) and Pb(II) at pH 6.0, dose 0.33 g/30 mL, initial concentration 300 mg/L, time 30 min and at 45 °C temperature using hydrothermal nanocomposite HTC/graphene oxide absorbent. The obtained results followed the sorption of heavy metal ions in a mixed-diffusion mode with the contribution of a second-order reaction between the active center of the sorbent and the metal ions. The Temkin and Dubinin-Radushkevich model’s parameters and thermodynamic results confirmed endothermic physical interactions among adsorbent and metal ions. This paper is highly useful for managing sunflower waste and purifying water; leading to the present demand for clean water and climatic issues. The production of the effective low-cost nanocomposite using green synthesis technologies (hydrothermal carbonization of raw materials) is highly useful for the removal of Cd(II) and Pb(II) toxic metal ions from water.

Temperature self-compensated fiber-optic Pb(II) sensor with improved selectivity by Resorcylaldehyde post-modified organic metal framework

Post-modification of metal-organic framework (MOF) materials is an effective means to enhance their efficient and selective adsorption for heavy metal ions. In this article, we presented a reflection-type optical fiber surface plasmon resonance (SPR) sensor based on dual core fiber (DCF) coated with UiO-66-RSA (UiO-66-NH2 post-modified with resorcinol aldehyde) film for the specific detection of Pb(II) in aqueous media. The composite material UiO-66-RSA exhibits stronger affinity and specificity for Pb(II) than UiO-66-NH2. The adsorption of Pb(II) can change the equivalent refractive index (RI) of UiO-66-RSA film, causing a regular shift in SPR spectra. Experiments have shown that the limit of detection (LOD) of the SPR Pb(II) sensor can reach 0.1 nM. Meanwhile, research has found that the SPR sensor is accompanied by temperature crosstalk of 0.356 nm/°C. Therefore, we constructed a Michelson temperature interferometer using polymer micro tips on the end face of the fiber core to achieve temperature compensation. Based on the above two sensing channels, dual parameter demodulation of Pb(II) concentration and temperature can be achieved with an error rate of less than 0.5 %. This article has potential research value in exploring the application of post modification techniques of MOF in fiber optic lead ion detection.