Efficient removal of lead (II) ions and methylene blue from aqueous solution using chitosan/Fe-hydroxyapatite nanocomposite beads

Monitoring Photo-Fenton and Photo-Electro-Fenton process of contaminants emerging concern by a gas diffusion electrode using Ca10-xFex-yWy(PO4)6(OH)2 nanoparticles as heterogeneous catalyst

The catalytic performance of modified hydroxyapatite nanoparticles, Ca10-xFex-yWy(PO4)6(OH)2, was applied for the degradation of methylene blue (MB), fast green FCF (FG) and norfloxacin (NOR). XPS analysis pointed to the successful partial replacement of Ca by Fe. Under photo-electro-Fenton process, the catalyst Ca4FeII1·92W0·08FeIII4(PO4)6(OH)2 was combined with UVC radiation and electrogenerated H2O2 in a Printex L6 carbon-based gas diffusion electrode. The application of only 10 mA cm-2 resulted in 100% discoloration of MB and FG dyes in 50 min of treatment at pH 2.5, 7.0 and 9.0. The proposed treatment mechanism yielded maximum TOC removal of ∼80% and high mineralization current efficiency of ∼64%. Complete degradation of NOR was obtained in 40 min, and high mineralization of ∼86% was recorded after 240 min of treatment. Responses obtained from LC-ESI-MS/MS are in line with the theoretical Fukui indices and the ECOSAR data. The study enabled us to predict the main degradation route and the acute and chronic toxicity of the by-products formed during the contaminants degradation.

Advanced applications of hydroxyapatite nanocomposite materials for heavy metals and organic pollutants removal by adsorption and photocatalytic degradation: A review

This comprehensive review delves into the forefront of scientific exploration, focusing on hydroxyapatite-based nanocomposites (HANCs) and their transformative role in the adsorption of heavy metals (HMs) and organic pollutants (OPs). Nanoscale properties, including high surface area and porous structure, contribute to the enhanced adsorption capabilities of HANCs. The nanocomposites' reactive sites facilitate efficient contaminant interactions, resulting in improved kinetics and capacities. HANCs exhibit selective adsorption properties, showcasing the ability to discriminate between different contaminants. The eco-friendly synthesis methods and potential for recyclability position the HANCs as environmentally friendly solutions for adsorption processes. The review acknowledges the dynamic nature of the field, which is characterized by continuous innovation and a robust focus on ongoing research endeavors. The paper highlights the HANCs' selective adsorption capabilities of various HMs and OPs through various interactions, including hydrogen and electrostatic bonding. These materials are also used for aquatic pollutants' photocatalytic degradation, where reactive hydroxyl radicals are generated to oxidize organic pollutants quickly. Future perspectives explore novel compositions, fabrication methods, and applications, driving the evolution of HANCs for improved adsorption performance. This review provides a comprehensive synthesis of the state-of-the-art HANCs, offering insights into their diverse applications, sustainability aspects, and pivotal role in advancing adsorption technologies for HMs and OPs.

A polyfunctionalized carbon framework composite for efficient decontamination of Cr(VI) and polycyclic aromatic nitrides from acidic wastewater

Developing multifunctional engineered adsorbents is an effective strategy for decontaminating the environment from various pollutants. In this study, a polyfunctionalized carbon-framework composite, MSC-CFM, was synthesized. The composite comprises an aromatic carbon framework enriched with various functional groups, including magnetic nanoparticles, hydroxyl, and amino groups. MSC-CFM was used to decontaminate Cr(VI) and polycyclic aromatic nitrides (p-dimethylaminoazobenzene sulfonate (DAS) and diphenyl-4, 4 '-di [sodium (azo-2 -) -1-amino-naphthalene-4-sulfonate] (DANS)) from acidic wastewater. The adsorption capacities of MSC-CFM for Cr(VI), DAS and DANS, quantified using the Langmuir isotherm model, were 161.28, 310.83, and 1566.09 mg/g, respectively. Cr(VI) and PAHs (DAS and DANS) were monolayer adsorbed controlled by chemisorption. MSC-CFM could maintain good adsorption efficiency after up to 6 adsorption and desorption cycles. The presence of polycyclic aromatic nitrides promoted the adsorption of Cr(VI) in the Cr(VI)-DAS/DANS binary systems. Removal of pollutants by MSC-CFM involved a variety of unreported reaction mechanisms, such as electrostatic attraction, redox reaction, anion exchange, intermolecular hydrogen bonding, complexation reaction, π-π interaction, and anion-π interaction. MSC-CFM, enriched with a variety of functional groups, is a promising new material for environmental protection. It has good potential for practical application in treating polluted wastewater.

Efficient removal of environmental pollutants by green synthesized metal nanoparticles of Clitoriaternatea

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4-nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10-3/min, 6.9 × 10-3/min, and 16.5 × 10-3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4-nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10-3/min, 1.8 × 10-3/min, and 1.7 × 10-3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.

Synthesis and characterization of copper nanoparticle-based hydrogel and its applications in catalytic reduction and adsorption of basic blue 3

Most of the dyes used in various industries are non-biodegradable and carcinogenic in nature. Therefore, elimination of dyes from textile wastes is mandatory to safeguard the life of human, aquatic animals and aquatic plants. In this connection an effective and eco-friendly hydrogel was synthesized from acrylamide, cellulose, clay, and copper salt abbreviated as AMPS(PHE-Ce)/MC-Cu. The fabricated hydrogel was used as sorbent and catalyst for the adsorption and catalytic reduction of basic blue 3. SEM analysis showed granular texture with small holes or cracks which is basic criteria for an adsorbent surface. The results showed that the BET surface area and the Langmuir surface area were, respectively, 27.87 and 40.32 m2/g. The FTIR analysis confirmed the synthesis of hydrogel, as is evident from peaks at 3500, 3439, 2996, 2414, and 1650 cm-1, which indicated the presence of OH or NH, -C-O-C-, CH3, (C[bond, double bond]O), C-N bonds correspondingly. Thermal stability was confirmed by TGA analysis where weight loss in three stages has been observed. The presence of copper was confirmed through EDX (5.02%) indicating the incorporation of cupper nanoparticles in hydrogel surface. The high adsorption capability of 1590 mg/g as recorded for basic blue-3 dye indicates it to be an efficient adsorbent. The swelling behavior characterized by Fickian diffusion up to 7898% clearly indicated significant swelling. Pseudo 2nd-order kinetics and the Langmuir isotherm models were more fit in unfolding kinetics and isothermal data indicating chemisorption with monolayer sorption as evident from the high R2 values (0.999) of each model. Thermodynamics considerations indicated that the adsorption process is endothermic with a positive enthalpy value of 1371.32 Jmol-1. The positive entropy value of 19.70 J/mol.K signifies a higher degree of disorder at the solid-liquid interface. The findings provided a valuable insights into the hydrogel's capacity to adsorb cationic dyes and reduce them catalytically, pointing towards its potential applications in addressing environmental challenges.

Simultaneous adsorption of Cu(II), Zn(II), Cd(II) and Pb(II) from synthetic wastewater using NaP and LTA zeolites prepared from biomass fly ash

Herein, NaP and LTA zeolites were successfully synthesised from woody biomass ash with alkali fusion-assisted hydrothermal method by altering the NaOH/ash ratio, crystallisation time and crystallisation temperature. In order to reduce the synthesis costs, NaP zeolite was synthesised with no additional source of aluminium and silicon. The synthesised zeolites were utilized for the monocomponent and simultaneous adsorption of Cu(II), Cd(II), Pb(II) and Zn(II) ions. The maximum adsorbed amount of metals had the trend Pb(II) > Cu(II) > Cd(II) > Zn(II) for both NaP and LTA zeolite. The kinetic data fit well to the pseudo-second order model indicating that chemisorption is the rate-limiting step. The isotherm data were well described with Sips and Redlich-Peterson models indicating a non-ideal heterogeneous adsorption process. Maximum adsorption capacity of NaP zeolite was 42.9 mg/g for Cu(II) and 117.3 mg/g for Cd(II), while LTA had 140.1 mg/g and 223.5 mg/g for Cu(II) and Cd(II) ions, respectively.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.

Next-Generation Water Treatment: Exploring the Potential of Biopolymer-Based Nanocomposites in Adsorption and Membrane Filtration

This review article focuses on the potential of biopolymer-based nanocomposites incorporating nanoparticles, graphene oxide (GO), carbon nanotubes (CNTs), and nanoclays in adsorption and membrane filtration processes for water treatment. The aim is to explore the effectiveness of these innovative materials in addressing water scarcity and contamination issues. The review highlights the exceptional adsorption capacities and improved membrane performance offered by chitosan, GO, and CNTs, which make them effective in removing heavy metals, organic pollutants, and emerging contaminants from water. It also emphasizes the high surface area and ion exchange capacity of nanoclays, enabling the removal of heavy metals, organic contaminants, and dyes. Integrating magnetic (Fe2O4) adsorbents and membrane filtration technologies is highlighted to enhance adsorption and separation efficiency. The limitations and challenges associated are also discussed. The review concludes by emphasizing the importance of collaboration with industry stakeholders in advancing biopolymer-based nanocomposites for sustainable and comprehensive water treatment solutions.

Efficient Removal of Hexavalent Chromium (Cr(VI)) from Wastewater Using Amide-Modified Biochar

The utilization of biochar, derived from agricultural waste, has garnered attention as a valuable material for enhancing soil properties and serving as a substitute adsorbent for the elimination of hazardous heavy metals and organic contaminants from wastewater. In the present investigation, amide-modified biochar was synthesized via low-temperature pyrolysis of rice husk and was harnessed for the removal of Cr(VI) from wastewater. The resultant biochar was treated with 1-[3-(trimethoxysilyl) propyl] urea to incorporate an amide group. The amide-modified biochar was characterized by employing Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. During batch experiments, the effect of various parameters, such as adsorbent dosage, metal concentration, time duration, and pH, on Cr(VI) removal was investigated. The optimal conditions for achieving maximum adsorption of Cr(VI) were observed at a pH 2, an adsorbent time of 60 min, an adsorbent dosage of 2 g/L, and a metal concentration of 100 mg/L. The percent removal efficiency of 97% was recorded for the removal of Cr(VI) under optimal conditions using amide-modified biochar. Freundlich, Langmuir, and Temkin isotherm models were utilized to calculate the adsorption data and determine the optimal fitting model. It was found that the adsorption data fitted well with the Langmuir isotherm model. A kinetics study revealed that the Cr(VI) adsorption onto ABC followed a pseudo-second-order kinetic model. The findings of this study indicate that amide-functionalized biochar has the potential to serve as an economically viable substitute adsorbent for the efficient removal of Cr(VI) from wastewater.

Cyclic desorption based efficacy of polyvinyl alcohol-chitosan variant resins for multi heavy-metal removal

The simultaneous removal of Cu, Pb and Fe from water bodies has been targeted in this work with polyvinyl alcohol (PVA) and chitosan (low, medium, and high molecular weight) derivative and with cyclic desorption efficacy target. For a varied range of adsorbent loading (0.2-2 g L^-1), initial concentration (187.7-563.1 mg L^-1 for Cu, 5.2-15.6 mg L^-1 for Pb, and 61.85-185.55 mg L^-1 for Fe), and resin contact time (5 to 720 min), batch adsorption-desorption studies were conducted. After first adsorption-desorption cycle, the optimum absorption capacity was 6.85 mg g^-1 for Pb, 243.90 mg g^-1 for Cu, and 87.72 mg g^-1 for Fe for the high molecular weight chitosan grafted polyvinyl alcohol resin (HCSPVA). The alternate kinetic and equilibrium models were analyzed along with the interaction mechanism between metal ions and functional groups. The cyclic desorption studies were carried out with simple eluent systems such as HCl, HNO₃, H₂SO₄, KOH, and NaOH. The experiments revealed that the HCSPVA derivative has been an impressive, reusable, and effective sorbent for the mitigation of Pb, Fe, and Cu in complex wastewater systems. This is due to its easy synthesis, excellent adsorption capacity, quick sorption rate, and remarkable regeneration capabilities.

A comprehensive review on the metal-based green valorized nanocomposite for the remediation of emerging colored organic waste

In today's era, "green" synthesis is an emerging research trend. It has gained widespread attention owing to its dynamic behavior, reliability, simplicity, sustainability, and environment friendly approach for fabricating various nanomaterials. Green fabrication of metal/metal oxides nanomaterials, hybrid materials, and other metal-based nanocomposite can be utilized to remove toxic colored aqueous pollutants. Nanomaterials synthesized by using green approach is considered to be the significant tool to minimize unwanted or harmful by-products otherwise released from traditional synthesis methods. Various kinds of biosynthesized nanomaterials, such as animal waste and plant-based, have been successfully applied and well documented in the literature. However, their application part, especially for the cure of colored organic polluted water, has not been reported as a single review article. Therefore, the current work aims to assemble reports on using novel biosynthesized green metal-based nanomaterials to exclude harmful dyes from polluted water.

Synchronous stabilization of As, Cd, and Pb in soil by sustained-release of iron-phosphate

Anionic arsenic (As) exhibits geochemical behavior opposite to those of cationic cadmium (Cd), and lead (Pb), which makes the synchronous remediation of As, Cd, and Pb challenging. The synchronous stabilization of As, Cd, and Pb to form Cd/Pb-phosphate and iron‑arsenic precipitates is a promising strategy. However, the effectiveness of soluble phosphate or iron-based materials is limited by the activation of Cd, Pb, or As, while low mobility hinders insoluble particles. In this study, we developed an amorphous structure that releases iron and phosphate at a sustained rate. Thus, the stabilization efficiencies of NaHCO₃-extractable As, DTPA-extractable Cd and Pb reached 44.6 %, 40.8 %, and 48.1 %, respectively. The proportion of residual fraction of As, Cd, and Pb increased by 12.1 %, 14.5 %, and 36.4 %, respectively, after 28 d. Ferrihydrite was chosen as the soil component to monitor the chemical behavior and speciation transformation of As, Cd, and Pb in the reaction. During the process, the released iron directly reacted with dissolved As to form iron‑arsenic precipitation and phosphate directly reacted with Cd/Pb to form Cd/Pb-phosphate precipitation. Simultaneously, phosphate replaced the adsorbed As and transformed into a dissolved state, which could be re-precipitated with the released iron ions. Thus, this study provides a reliable strategy for the remediation of As, Cd, and Pb combined pollution in soil.

Manganese-doped hydroxyapatite as an effective adsorbent for the removal of Pb(II) and Cd(II)

The water polluted by lead(Pb(II)) and cadmium(Cd(II)) seriously endangers ecological safety and needs to be solved urgently. Because of the relatively low adsorption rate of pure hydroxyapatite for heavy metals, a series of manganese-doped hydroxyapatites (MnHAPs) were prepared by using manganese, a common impurity in hydroxyapatite, as a doping element to improve the adsorption performance. The structural and functional groups of the materials with different Mn/(Ca +Mn) molar ratios (0%, 5%, 10%, 20%, and 30%) were investigated by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), X-Ray diffraction (XRD), Raman spectrometer and Fourier transform infrared spectroscopy (FTIR) characterization. The presence of manganese influenced the formation and growth of hydroxyapatite crystals, resulting in lattice distortion and a large number of lattice defects in materials. Among them, manganese-doped hydroxyapatite with a Mn/(Ca +Mn) molar ratio of 10% (MnHAP-10) could most effectively remove Pb(II) and Cd(II), with the adsorption capacity of 1806.09 mg g^-1 for Pb(II) at pH = 5 and 176.88 mg g^-1 for Cd(II) at pH = 5.5. Then the adsorption behavior and mechanism were further researched systemically. It was concluded that the immobilization of Pb(II) by MnHAP-10 was mainly through dissolution precipitation and ion exchange, while Cd(II) was adsorbed by ion exchange and electrostatic interaction. In conclusion, MnHAP-10 has the potential to be applied as an effective adsorbent for the removal of Pb(II) and Cd(II) pollution.

Multi-ionic interaction with magnesium doped hydroxyapatite-zeolite nanocomposite porous polyacrylonitrile polymer bead in aqueous solution and spiked groundwater

Removal of multi-ionic contaminants from water resources has been a major challenge faced during the treatment of water for drinking and industrial applications. In the present study, varying composition of magnesium doped hydroxyapatite (Mg-HAp) and zeolite nanocomposite embedded porous polymeric beads were synthesized using solvent displacement method and its sorption efficiency towards multi-ion contaminant (such as Ag, Al, As, Ba, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Tl, Th, U, V and Zn) was investigated in aqueous solution and spiked groundwater. The prepared beads were characterized using suitable techniques like high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) equation. The surface area and pore radius of the beads varied from 6.996 to 66.469 m²/g and 1.698-3.960 nm respectively according to the composition of the bead. The control bead without nanocomposite showed maximum surface area. Multi-ion adsorptions onto beads were confirmed using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES) and X-ray photoelectron spectrophotometer (XPS). The sorption efficiency was high at pH 5 owing to its anionic surface charge leading to an increase in affinity towards the cations. For validating field application, selected high performance beads were tested in multi-ion spiked groundwater. The results indicated that the Mg-HAp nanocomposite bead dominate all the other bead compositions with more than 90% removal efficiency for most of the multi-ion contaminants. The feasible adsorption mechanism has been discussed. This adsorption study revealed that the Mg-HAp nanocomposite bead is a promising material that is cost-effective, non-toxic, biodegradable, eco-friendly and highly efficient towards the removal of multi-ionic contaminants from groundwater.

Fabrication of attapulgite-based dual responsive composite hydrogel and its efficient adsorption for methyl violet

In this work, attapulgite (ATP)-based dual sensitive poly (N-isopropylacrylamide-co-acrylic acid) composite hydrogel, P(NIPAM-co-AA)/ATP, was prepared by free radical polymerization. The prepared composite hydrogel was characterized via methods of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta potential analysis and Brunauer, Emmett, and Teller (BET) etc. The composite hydrogel showed pH and temperature sensitive behaviour, with lower critical solution temperature (LCST) of 35°C and highest swelling occurred at pH 8.0. The adsorption of methyl violet (MV) can be controlled by the hydrogel responsiveness, and 95.78% of MV can be removed at pH 8.0 and 35°C. The addition of a small amount of ATP (3 Wt%) can improve the swelling ratio and adsorption capacity. Kinetic analysis demonstrated that the experimental data were best fitted to the pseudo-second order model. Isotherm analysis showed that the equilibrium data followed Langmuir model with the adsorption capacity of 168.35 mg g^-1. In addition, the composite hydrogel has high adsorption selectivity for cationic dyes, and MV-loaded hydrogel is easy to regenerate, which can be used for successive adsorption cycles. These results demonstrate that the composite hydrogel has potential application in dye wastewater treatment.

The Utilization of Modified Zeolite for the Removal of Cs Ions in an Aqueous Solution: Adsorption Capacity, Isotherms, Kinetics and Microscopic Studies

Nuclear energy is a double-edged technology, which has a significant role in the chemical industry, but may bring about radioactivity and destruction. The 2011 Fukushima nuclear power plant accident caused by a tsunami, which flooded and led to tens of millions of disaster debris and tsunami deposits, severely disrupted the electricity supply in Japan and induced USD 211 billion worth of direct economic losses. Cs+ was easily dissolved in this accident, had a high chemical activity, and thus required an appropriate adsorption method. Zeolite is an effective removal adsorbent, which is suitable to be investigated. The present study uses natural zeolite and three inorganic modified zeolites. Furthermore, the effects of various factors are investigated. Kinetic models and the isothermal adsorption mechanism are also conducted. For microscale studies for the adsorption mechanism, scanning electron microscope (SEM) and X-ray diffraction (XRD) were involved in the study. The results indicate that the optimal dosage is 1.1 g and the maximum adsorption rate is around 80%. An alkaline environment is more conducive to the occurrence of adsorption. As for the isotherm and kinetic studies, the data fits better with the Redlich–Peterson isothermal model and intragranular diffusion model. In this small-scale experiment, the highest adsorption capacity was for Mg-zeolite at 6.53 mg/g. Finally, Mg-Zeolite presents the best adsorption capacity.

Green method to synthesize magnetic zeolite/chitosan composites and adsorption of hexavalent chromium from aqueous solutions

This paper aims to synthesis a recyclable adsorbent from solid waste using a clean and environmentally friendly method to deal with Cr(VI) water pollution. Magnetic zeolite/chitosan composites (ZFA/MCS) were prepared by the neutralization method. The adsorption properties of ZFA/MCS, prepared by the neutralization method for Cr(VI) ions under different conditions especially cross-linking, were investigated in detail. The results showed that cross-linked ZFA/MCS generally showed higher adsorption capacity than uncross-linked ones. The uncross-linked ZFA/MCS and cross-linked ZFA/MCS showed a saturated adsorption capacity of 25.67 mg·g^-1 and 28.47 mg·g^-1 at pH = 3 and 30 °C, respectively. The experimental values were followed Langmuir adsorption equations and pseudo-second-order kinetic model, indicating that the adsorption was probably monolayer coverage and chemical adsorption, respectively. The effect of temperature proved that the adsorption was spontaneous and endothermic. Therefore, the adsorbent with excellent recyclability and adsorbability was successfully fabricated via a green synthetic strategy.

Efficient Removal of Pb(II) from Aqueous Medium Using Chemically Modified Silica Monolith

The adsorptive removal of lead (II) from aqueous medium was carried out by chemically modified silica monolith particles. Porous silica monolith particles were prepared by the sol-gel method and their surface modification was carried out using trimethoxy silyl propyl urea (TSPU) to prepare inorganic–organic hybrid adsorbent. The resultant adsorbent was evaluated for the removal of lead (Pb) from aqueous medium. The effect of pH, adsorbent dose, metal ion concentration and adsorption time was determined. It was found that the optimum conditions for adsorption of lead (Pb) were pH 5, adsorbent dose of 0.4 g/L, Pb(II) ions concentration of 500 mg/L and adsorption time of 1 h. The adsorbent chemically modified SM was characterized by scanning electron microscopy (SEM), BET/BJH and thermo gravimetric analysis (TGA). The percent adsorption of Pb(II) onto chemically modified silica monolith particles was 98%. An isotherm study showed that the adsorption data of Pb(II) onto chemically modified SM was fully fitted with the Freundlich and Langmuir isotherm models. It was found from kinetic study that the adsorption of Pb(II) followed a pseudo second-order model. Moreover, thermodynamic study suggests that the adsorption of Pb(II) is spontaneous and exothermic. The adsorption capacity of chemically modified SM for Pb(II) ions was 792 mg/g which is quite high as compared to the traditional adsorbents. The adsorbent chemically modified SM was regenerated, used again three times for the adsorption of Pb(II) ions and it was found that the adsorption capacity of the regenerated adsorbent was only dropped by 7%. Due to high adsorption capacity chemically modified silica monolith particles could be used as an effective adsorbent for the removal of heavy metals from wastewater.

Adsorption of As(III), Pb(II), and Zn(II) from Wastewater by Sodium Alginate Modified Materials

Sodium alginate (SA), polyvinyl oxide (PEO), and ceramic nanomaterials were used to prepare alginate composite gel. The present study examined the removal rate and adsorption capacity of alginate composite gel for removal of wastewater As(III), Pb(II), and Zn(II). Batch experiments were conducted to study the influence of experimental parameters such as pH and temperature, as well as the mechanism of As(III), Pb(II), and Zn(II) adsorption with the new adsorbent. The results showed the high efficiency of sodium alginate composite gel for removal of wastewater As(III), Pb(II), and Zn(II). Under the condition of the best liquid-solid ratio and the contact time, the removal rates of As(III), Pb(II), and Zn(II) were 67.42%, 95.31%, and 93.96%, respectively. The pseudo-second-order kinetic equation was superior to fit the adsorption kinetics process. The isothermal adsorption models of As(III) and Pb(II) fitted well with the Freundlich model, and Zn(II) fitted well with the Langmuir model. The results of SEM, EDS, XPS, and FTIR analyses revealed that the adsorption process occurred mainly via chemisorption. The results of the present study suggest that new adsorbents can be effectively utilized for As(III), Pb(II), and Zn(II) removal from water.

Super adsorption performance of carboxymethyl cellulose/copper oxide-nickel oxide nanocomposite toward the removal of organic and inorganic pollutants

A novel nanocomposite bead based on polymeric matrix of carboxymethyl cellulose and copper oxide-nickel oxide nanoparticles was synthesized, characterized, and applied for adsorptive removal of inorganic and organic contaminants at trace level of part per million (mgL^-1) from aqueous sample. Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) adsorbent beads were selective toward the removal of Pb(II) among other metal ions. The removal percentage of Pb(II) was more than 99% with 3 mgL^-1. The waste beads after Pb (II) adsorption (Pb@CMC/CuO-NiO) and CMC/CuO-NiO nanocomposite beads were employed as adsorbents for removing of various dyes. It was found that Pb@CMC/CuO-NiO can be reused as adsorbent for the removal of Congo Red (CR), while CMC/CuO-NiO nanocomposite beads were more selective for removal of Eosin Yellow (EY) from aqueous media. The adsorption of CR and EY was optimized, and the removal percentages were 93% and 96.4%, respectively. The influence of different parameters was studied on the uptake capacity of Pb(II), CR, and EY, and lastly, the CMC/CuO-NiO beads exhibited responsive performance in relation to pH and other parameters. Thus, the prepared CMC/CuO-NiO beads were found to be a smart material which is effective and played super adsorption performance in the removal of Pb(II), CR, and EY from aqueous solution. These features make CMC/CuO-NiO beads suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial adsorbents.

Adsorption of cationic dyes, drugs and metal from aqueous solutions using a polymer composite of magnetic/β-cyclodextrin/activated charcoal/Na alginate: Isotherm, kinetics and regeneration studies

In this work, we successfully synthesized novel polymer gel beads based on functionalized iron oxide (Fe3O4), activated charcoal (AC) particles with β-cyclodextrin (CD) and sodium alginate (SA) polymer (Fe3O4/CD/AC/SA), by a simple, reproducible and inexpensive method. These beads proved to be versatile and strong adsorbents with magnetic properties and high adsorption capacity. The composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometry, adsorption at -196 °C, high resolution transmission electron microscopy, thermogravimetric analysis and point of zero charge measurements. Two dyes, two drugs and one metal were used to test the adsorption capability of the prepared polymer nanocomposite. The adsorbent showed good removal efficiencies for the studied pollutants, especially the cationic dyes and the metal, when compared to other low-cost adsorbents. The saturated adsorption capacity of Fe3O4/CD/AC/SA reached 5.882 mg g-1 for methyl violet (MV), 2.283 mg g-1 for brilliant green (BG), 2.551 mg g-1 for norfloxacin (NOX), 3.125 mg g-1 for ciprofloxacin (CPX), 10.10 mg g-1 for copper metal ion (Cu(II)). The adsorption isotherm studies showed that data fitted well with Langmuir and Temkin isotherms models. The kinetic data showed good correlation coefficient with low error function for the pseudo-second order kinetic model. The data analysis was carried out using error and regression coefficient functions for the estimation of best-fitting isotherm and kinetic models, namely: chi-square test (χ2) and sum of the squares of errors (SSE). The activation energy was found to be 47.68 kJ mol-1 for BG, 29.09 kJ mol-1 for MV, 28.93 kJ mol-1 for NOX, 4.53 kJ mol-1 for CPX and 17.08 kJ mol-1 for Cu(II), which represent chemisorption and physisorption behavior of sorbent molecules. The polymer composites can be regenerated and easily separated from aqueous solution without any weight loss. After regeneration, the Fe3O4/CD/AC/SA beads still have good adsorption capacities up to four cycles of desorption and adsorption. The results indicate that the polymer gel beads are promising adsorbents for the removal of different categories of toxicants (like dyes, drugs and metal) in single adsorbate aqueous systems. Thus, the novel Fe3O4/CD/AC/SA beads can be effectively employed for a large-scale applications as environmentally compatible materials for the adsorption of different categories of pollutants.

Activated carbon-alginate beads impregnated with surfactant as sustainable adsorbent for efficient removal of methylene blue

A cost-effective and sustainable Calligonum polygonoides biomass based activated carbon (AC) was synthesized. The prepared AC was utilized in the fabrication of carbon-alginate beads for the adsorption of methylene blue (MB) textile dye from aqueous solution. The surface morphology, surface functional groups, elemental analysis and thermal behavior of the prepared beads were investigated using different analytical techniques. Batch adsorption experiments were performed to investigate the adsorption capacity of the beads. Effect of different parameters such as initial pH of MB solution, dose of adsorbent, contact time, initial concentration of MB and temperature were evaluated. The kinetic studies identified pseudo-second order model. Langmuir and Freundlich isotherm models were applied and fitted to the experimental equilibrium data. The beads showed a maximum adsorption capacity of 769 mg/g in basic pH at 30 °C while using 400 mg·L^-1 of MB solution. The adsorption process was found to be endothermic and spontaneous as confirmed by the thermodynamic data. The fabricated beads were subjected to recycling which exhibited same adsorption efficiency after six regeneration cycles. The results showed that the AC-alginate beads impregnated with SDS have high adsorption capability and would be used for the efficient removal of cationic dyes from wastewater.

An Amberlite IRA-400 Cl- ion-exchange resin modified with Prosopis juliflora seeds as an efficient Pb2+ adsorbent: adsorption, kinetics, thermodynamics, and computational modeling studies by density functional theory

A Prosopis juliflora-seed-modified Amberlite IRA-400 Cl- ion-exchange resin (hereafter denoted as SMA resin) is used for the removal of Pb2+ from wastewater. SEM, EDX, FT-IR, BET, XRD, and XPS analyses were used to characterize the SMA resin. Parameters such as Pb2+ concentration, pH, temperature, and time are optimized. The obtained results show that the SMA resin has high efficiency for the removal of Pb2+ (73.45%) at a concentration of 100 mg L-1 and a dosage of 0.01 g at pH 6. Thermodynamic studies indicate that the adsorption was spontaneous with negative ΔH° and ΔS° values at all temperatures; pseudo-second-order kinetics and the Langmuir adsorption isotherm provided the best fit (q max = 106 mg g-1 and R 2 = 0.99) from 298 to 338 K. In addition, a diffusion-controlled mechanism at 298 K was observed from intra-particle studies. A desorption and recovery process has been applied successfully to the SMA adsorbent. The obtained results showed desorption of 90.7% at pH 2.5 with 86.3% recovery over six cycles. Furthermore, the DFT results suggest that all the functional groups of the SMA resin possibly bind with Pb2+ and, of these, the -C[double bond, length as m-dash]O group shows the highest binding energy towards Pb2+. Moreover, the high-efficiency removal of Pb2+ from synthetic wastewater using the proposed SMA resin was demonstrated to show the real-life application potential.

Fish scale-extracted hydroxyapatite/chitosan composite scaffolds fabricated by freeze casting-An innovative strategy for water treatment

In this study, low-cost and eco-friendly hydroxyapatite (HA) minerals were extracted from scales of Tilapia fish (Oreochromis mossambicus). After calcination, fish-scale extracted powder was further confirmed to be HA by X-ray diffraction with mean particle size of 5.96 μm determined by particle size analyzer. The calcined powder was utilized as the raw material and combined with chitosan (CS) to synthesize composite scaffolds by freeze casting and cross-linking. Mercury porosimetry results showed that the scaffolds possessed hierarchical porous structure. Microstructural features characterized by SEM revealed unidirectional channel structures with channel sizes ranged from 10 to 100 μm and 1 to 50  μm for scaffolds freeze-casted at 2 ℃/min and 5 ℃/min cooling rates, respectively. The adsorption kinetics of HA/CS composite scaffolds with varying channel sizes were investigated by both batch and fixed-bed processes with different Pb(П) initial concentrations (100 and 1000 mg/L). The adsorption capability was optimized by tuning the cooling rates and the maximum adsorption amount could reach 75-570 mg/g in batch process and 94 mg/g in fixed bed process. In summary, the HA/CS composite scaffolds showed great capability to remove heavy metal ions from waste water and their tunable channel sizes could be applied in suitable fields under both statistic and flowing conditions.

Luffa sponge-derived hierarchical meso/macroporous boron nitride fibers as superior sorbents for heavy metal sequestration

Boron nitride (BN) has received tremendous attention as a promising adsorbent material. However, unsatisfactory uptake capacities over heavy metal ions limit their practical applications. Herein, we have synthesized a novel hierarchical meso/macroporous BN fibers (MBNFs) via a simple carbothermal reduction method using luffa sponge as a template. The as-obtained MBNFs comprise densely arranged parallel macrochannels on a micrometer scale, with mesopores on the surface of the channel. The resulting MBNFs exhibited remarkable adsorption performance for different heavy metal ions including Cd²⁺, Zn²⁺, Cr³⁺, and Pb²⁺ with maximum uptake capacities as high as 2989, 1885, 723, and 453 mg/g, respectively. In particular, the adsorption capacity for Cd²⁺ and Zn²⁺ exceed the highest values reported for BN materials. In addition, the MBNFs showed excellent stability to re-use for a few times. The present MBNFs materials prepared using cheap and earth abundant luffa sponge may find broad applications such as adsorbent for environmental remediation applications.

Evaluation of hybrid neutralization/biosorption process for zinc ions removal from automotive battery effluent by dolomite and fish scales

This work focused in the evaluation of Oreochromis niloticus fish scales (FS) as biosorbent material in the removal of Zn from a synthetic effluent based on automotive battery industry effluent and, further, a hybrid neutralization/biosorption process, aiming at a high-quality treated effluent, by a cooperative use of dolomite and FS. For this, a physicochemical and morphological characterization (i.e. SEM-EDX, FTIR, XRD, and TXRF) was performed, which helped to clarify a great heterogeneity of active sites (phosphate, carbonate, amide, and hydroxyl) on the biosorbent; also the inorganic constituents (apatites) leaching from the FS was identified. Biosorption results pointed out to a pH-dependent process due to changes in the functional group's anionic character (i.e. electrostatic interactions), where an initial pH = 3 favored the Zn uptake. Kinetic and equilibrium studies confirmed the heterogeneous surface and cooperative sorption, wherein experimental data were described by Generalized Elovich kinetic model and the favorable isotherm profile by Langmuir-Freundlich isotherm ( qmax  = 15.38 mg g^-1 and 1/n>1 ). Speciation diagram of Zn species along with the leached species demonstrated that, for the studied pH range, the biosorption was the most likely phenomena rather than precipitation. Finally, the hybrid neutralization/biosorption process showed great potential since both the Zn concentration levels and the pH reached the legislation standards (C_Zn = 4 mg L^-1; pH = 5). Hence, based on the characterization and biosorption results, a comprehensive evaluation of the involved mechanisms in such complex system helped to verify the prospective of FS biosorbent for the Zn treatment from solution, in both individual and hybrid processes.

Successive removal of Pb2+ and Congo red by magnetic phosphate nanocomposites from aqueous solution

The successive removal of Pb²⁺ and Congo red (CR) from aqueous solution by three magnetic phosphate nanocomposites (Fe₃O₄@Sr₅(PO₄)₃(OH), Fe₃O₄@Ba₃(PO₄)₂, and Fe₃O₄@Sr_5xBa_3x(PO₄)₃(OH), denominated FSP, FBP, and FSBP, respectively) was systematically investigated in comparison with Fe₃O₄ (denominated F) nanoparticle. FSP, FSBP, F, and FBP exhibited a high removal capacity of 351, 272, 76, and 23 mg/g for Pb²⁺, respectively. These materials could be reclaimed by magnetic separation and then used for successive CR remediation, showing a high CR removal capacity of 224, 163, 126, and 61 mg/g, respectively. The isothermal and kinetic behavior fitted well with the Langmuir model and pseudo-second-order model, respectively. The successive removal mechanism by these magnetic phosphates was proposed to be the ion exchange between Pb²⁺ and Sr²⁺ in the lattice and then the loaded Pb²⁺ could contact with anionic dye CR to form precipitation on the surface of materials, inhibiting the leaching of Pb²⁺ ions from the reclaimed materials back into water. In addition, these materials showed good reusability and practical application. This study demonstrated the potential of these low cost phosphate nanocomposites as promising materials for successive removal of Pb²⁺ and CR from water.

Adsorptive removal of Pb (II) by means of hydroxyapatite/chitosan nanocomposite hybrid nanoadsorbent: ANFIS modeling and experimental study

In the current study, the prediction efficiency of lead adsorption by highly functional nanocomposite adsorbent of hydroxyapatite (HAp)/chitosan using ANFIS system was investigated. In this regard, the nanocomposite was applied in order to investigate the lead adsorption capacity. The operational conditions were pH (2-6), contact time between lead ions and adsorbent (15-360 min), shaker velocity (80-400 rpm), temperature (25-55 °C), amount of adsorbent (0.01-1.5 g), lead initial concentration (0-5000 ppm) and HAp concentration (10-75%). The effect of each parameter was investigated, and then the ANFIS was employed to model the adsorption process using the obtained experimental results. The ANFIS modeled the results with total average error and total average of absolute error less than 0.0646% and 4.2428%, respectively, for training data. Moreover, the coefficient of determination for training data and testing data were found to be 0.9999 and 0.9823, respectively. In addition, granular chitosan and HAp nanoparticles adsorption capabilities were compared with nanocomposite of HAp (20%wt)/chitosan adsorbent. It was found that nanocomposite adsorbent had a higher adsorption capability than other adsorbents.

Biosorption of Pb(II) ions from aqueous solution using alginates extracted from Djiboutian seaweeds and deposited on silica particles

High-molecular alginates were extracted from Djiboutian brown seaweeds, Sargassum sp. (S) and Turbinaria (T) and isolated as sodium salts in 31.0 and 42.7% yield by weight. 1H NMR analysis of the uronic acid block-structure indicates mannuronic/guluronic M/G ratios of 0.49 and 3.0 for the alginates extracts, respectively. The resulting alginates were deposited onto native Aerosil 200 silica, amine-functionalized and carboxyl-functionalized silica particles to enhance the mechanical strength providing Alg.(T/S)+SiO2) Alg.(T/S)+SiO2NH2) and Alg.(T)+SiO2CO2H) composites. Taking Pb(II) as examples for toxic heavy metal ions, the effects of the pH, adsorption kinetics, and isotherms have been studied systematically. The best uptake achieved was 585 mg Pb2+ ion/g using Alg.S+SiO2NH2. Furthermore, the Pb(II) ions were successfully desorbed in several cycles from Alg.T+SiO2 using 0.5 M hydrochloric acid. Therefore, Alg.T+SiO2 may be considered as a low-cost biosorbent that quickly adsorbs and easily desorbs analyte lead ions. A comparison of the adsorption capacity of our biopolymer-coated particles with that of other adsorbents reported in the literature reveals that our materials are among the best performing for the adsorption of Pb(II).

Lead Remediation Using Smart Materials. A Review

The nanoparticles have been prepared and employed as excellent adsorbents for the sequestration of heavy metal ions and hazardous impurities from the aqueous media. The surface morphological, textural and structural properties of nanoparticles have been modified, which are capable and potentially useful for the remediation of metal ions. Several metals (oxides, doped, nanocomposites of Fe, Ti, Zn, SiO2, SiC, Mo, Co, Ni, Zr, Mn, Si, S, Al, Cu, Ce, graphene, CNTs) were reported an efficient adsorbents for the removal of lead (Pb) ions from aqueous media and polluted water. The present review focuses on different kinds of nanoparticles such as metal oxides, carbon based and host supported employed for removal of Pb ions under varying experimental conditions such as pH, temperature, contact time and concentrations. The preparation strategies, physicochemical properties and adsorption are also discussed. Based on studies, it was found that the smart materials are affective adsorbents for the purification of wastewater containing Pb ions and could possibly extended for the remediation of other heavy metal ions.

Hydrazinolyzed cellulose-g-polymethyl acrylate as adsorbent for efficient removal of Cd(II) and Pb(II) ions from aqueous solution

Hydrazinolyzed cellulose-graft-polymethyl acrylate (Cell-g-PMA-HZ), an efficient adsorbent for removal of Cd(II) and Pb(II) from aqueous solution, has been prepared by ceric salt-initiated graft polymerization of methyl acrylate from microcrystalline cellulose surface and subsequent hydrazinolysis. The influences of initial pH, contact time, and temperature on adsorption capacity of Cell-g-PMA-HZ as well as adsorption equilibrium, kinetic and thermodynamic properties were examined in detail. As for Cd(II) adsorption, kinetic adsorption can be explained by pseudo-second-order, while adsorption isotherm fits well with Langmuir isotherm model, from which maximum equilibrium adsorption capacity can be derived as 235.85 mg g^-1 at 28 °C. Further thermodynamic investigation indicated that adsorption of Cd(II) by adsorbent Cell-g-PMA-HZ is endothermic and spontaneous under studied conditions. On the other hand, isotherm of Pb(II) adsorption fits well with Freundlich isotherm model and is more likely to be a physical-adsorption-dominated process. Consecutive adsorption-desorption experiments showed that Cell-g-PMA-HZ is reusable with satisfactory adsorption capacity.

Removal of bisphenol A and some heavy metal ions by polydivinylbenzene magnetic latex particles

In this study, magnetic polydivinylbenzene latex particles MPDVB with a core-shell structure were tested for the removal of bisphenol A (BPA), copper Cu(II), lead Pb(II), and zinc Zn(II) from aqueous solutions by a batch-adsorption technique. The effect of different parameters, such as initial concentration of pollutant, contact time, adsorbent dose, and initial pH solution on the adsorption of the different adsorbates considered was investigated. The adsorption of BPA, Cu(II), Pb(II), and Zn(II) was found to be fast, and the equilibrium was achieved within 30 min. The pH 5-5.5 was found to be the most suitable pH for metal removal. The presence of electrolytes and their increasing concentration reduced the metal adsorption capacity of the adsorbent. Whereas, the optimal pH for BPA adsorption was found 7, both hydrogen bonds and π-π interaction were thought responsible for the adsorption of BPA on MPDVB. The adsorption kinetics of BPA, Cu(II), Pb(II), and Zn(II) were found to follow a pseudo-second-order kinetic model. Equilibrium data for BPA, Cu(II), Pb(II), and Zn(II) adsorption were fitted well by the Langmuir isotherm model. Furthermore, the desorption and regeneration studies have proven that MPDVB can be employed repeatedly without impacting its adsorption capacity.

Preparation of Magnetic Carboxymethylchitosan Nanoparticles for Adsorption of Heavy Metal Ions

The remediation of metal and heavy metal contaminants from water ecosystems is a long-standing problem in the field of water management. The development of efficient, cost effective, and environmentally friendly natural polymer-based adsorbents is reported here. Magnetic chitosan (CS) and carboxymethylchitosan (CMC) nanocomposites have been synthesized by a simple one-step chemical coprecipitation method. The nanoparticles were assessed for the removal of Pb²⁺, Cu²⁺, and Zn²⁺ ions from aqueous solution. Kinetic and thermodynamic models were used to describe and understand the adsorption process of the ions onto the nanomaterials. The interactions between the ions and the biopolymer-based composites are reversible, which means that the nanoparticles can be regenerated in weakly acidic or EDTA containing solution without losing their activity and stability for water cleanup applications.