Adsorption Efficiency Research Articles

Bioremediation Using Fruit Waste to Remove Lead From Water

ABSTRACTThe application of biomaterials in the remediation of contaminated water requires studies that support their use, involving physical, chemical, and/or biological treatments. This study aimed to physicochemically characterize the adsorption process of biomaterials created from orange peels, tamarind seeds, and avocado seeds when they interact with lead to remove it from water. Additionally, we compared the adsorption efficiency between materials subjected to physical processes and chemical processes (polymerized with polyanilines). Our results indicate that orange peel is the best option for Pb(II) concentrations lower than 100 mg L−1, whereas avocado seeds offer better adsorption results for higher concentrations, followed by tamarind seeds. The results show that Freundlich isotherms best describe the adsorption process. The Fourier Transform Infrared spectra indicate that chemisorption is the dominant mechanism. This is supported by comparing the adsorption capacity of the biomaterial with that of the biomaterial polymerized with polyanilines; this process reduces adsorption by up to 40% due to the diminution of active sites. The optimal pH for orange peel and tamarind seeds is 4.5, whereas for avocado it is 6.0, which coincides with the pKa of carboxyl groups. The infrared spectra suggest that the interaction occurs in the carboxyl groups.

Adsorption of fluoxetine in aqueous environments: Development of macroporous cryogels based on sodium poly(acrylate) and carboxymethyl chitosan

This study focuses on the development of macroporous monoliths using cryopolymerization of sodium acrylate/carboxymethyl chitosan solutions for the adsorption of the antidepressant fluoxetine in aqueous environments. The cryogels were characterized using various analytical techniques, and the effects of pH, temperature, initial concentration, and contact time on the adsorption capacity were investigated. The surface charge of the cryogel was negative when pHsolution > pHPZC, and pH 8.5 was optimal for swelling rates and fluoxetine removal efficiency. The NaPA4-CMCs cryogel (0.5 mg.mL−1) showed the best adsorption performance, with the pseudo-first-order model best describing the experimental kinetics data. The intraparticle diffusion model revealed rapid diffusion through macropores and mesopores. The Langmuir model fitted well to the experimental adsorption equilibrium data, with qmax = 80.6 ± 3.4 mg.g−1. The adsorption process was favorable, exothermic, and governed by physisorption, involving electrostatic, hydrogen bonding, π–π, and hydrophobic interactions. The binary solvent HCl (0.1 M)/methanol 1:1 v/v was effective for regenerating the adsorbent, with adsorption efficiency greater than 60 % after three cycles of reuse. The study highlights the potential of these macroporous monoliths for the effective removal of antidepressants from aqueous environments.

Experimental overview of nanoferrites: synthesis, characterization and performance evaluation in wastewater treatment

Abstract This study investigates the potential of ferrite nanoparticles (BaFe12O19, MnFe2O4, NiFe2O4, and Co1–0.5Ni0.5Fe2O4) as eco-friendly adsorbents for the removal of heavy metals (Zn2+, Ni2+, Co2+, and Mn2+) from wastewater. Moreover, the adsorption experiments were conducted under varying contact times (30 min, 1 h, 2 h, and 4 h) and pH levels (2, 7, and 12) for five cycles to evaluate their significant dynamic effects on the removal efficiency. All ferrite nanoparticles were synthesized by the co-precipitation method and characterized (XRD, FT-IR, and SEM) to ascertain their crystal structure, morphology, size distribution, and crystallographic structures before wastewater treatments. The results demonstrated that BaFe12O19 had a particle size of 8.65 nm and achieved maximum adsorption ability of 93%, 91%, 94%, and 91% for Zn2+, Ni2+, Co2+, and Mn2+, respectively, at a pH of 7 after 4 h of treatment. Since the neutral pH value affects the binding of heavy metal ions, therefore governing the adsorption efficiency and selectivity. In contrast, NiFe2O4 (1.41 nm) revealed maximum removal of Zn2+, Ni2+, Co2+, and Mn2+ were 78%, 71%, 88%, and 83%, respectively, at a pH of 12 after 4 h. This was attributed to the negatively charged surface leading to stronger electrostatic attractions between the positively charged metal ions and the adsorbent surface, resulting in higher adsorption uptake. Notably, the higher removal rate of ions was observed during initially 1 h, suggesting a decline in efficiency rate with extended treatment time. Additionally, the experimental study over five cycles concluded that the adsorbent could be effectively regenerated and reused.

Preparation of activated biochar from durian shells for the extraction of phytohormones from waste coconut water via adsorption

Abstract The demand for activated carbon increases due to its effectiveness in wastewater treatment and other soil applications. However, its growing demand in the market resulted to higher price, thus, this study aimed to develop a cheaper alternative. The use of agricultural waste for biochar production has been the focus of several studies nowadays. Aside from the cheaper cost of the feedstock and the process, the problem on waste generation in the country will be lessened. In this study, activated biochar derived from Durian (Durio zibethinus) shells was prepared as adsorbent for the extraction of phytohormones from waste coconut water. Phytohormones or plant hormones are all-natural substitute to synthetic plant growth regulators (PGRs) used for different tissue culture practices in the country. Chemical activation conditions (alkali-to-raw biochar ratio and holding time) were determined to maximize phytohormone adsorption efficiency of the activated biochar. The activation of the durian shell-derived biochar was done using potassium hydroxide as chemical activating agent. Factors such as KOH-biochar ratio (high level: 5:1 (w/w), low level: 1:1 (w/w) ) and carbonization holding time (high level: 90 mins, low level: 45 mins) were applied to test its significance on the activation of durian shell biochar with percent phytohormones removal from waste coconut water as a response. The parametric study showed that KOH-biochar ratio as a main effect was significant and its interaction with holding time was also significant. This result will be used in the ongoing study to produce optimized activated biochar and will be used for batch and column adsorption. The prepared durian shell activated biochar will then be used for the extraction of phytohormones from waste coconut water via adsorption.

2‐Oxazoline‐Based Polymer for Pharmaceutical Products Adsorption in Aqueous Media

ABSTRACTWe present the synthesis and comprehensive evaluation of a novel 2‐oxazoline‐based polymer (polyPhOx) functionalized with phenyl groups, designed for the efficient adsorption of pharmaceutical contaminants from aqueous solutions. Employing living polymerization techniques (CROP) with two distinct initiators, we optimize reaction parameters including time, temperature, and initiator concentration. The rigorous characterization of the obtained polymer is depicted as well as the demonstration of its significant binding capacity for various pharmaceuticals, exploiting π–π and electrostatic interactions to achieve superior adsorption efficiency. Adsorption experiments are performed using high concentrations of model pharmaceuticals, including aspirin, ibuprofen, metoclopramide, pyramidone, oestradiol, and indomethacin, in hydroalcoholic solutions. Initial investigations confirm polyPhOx's exceptional efficacy, particularly with hydrophobic compounds such as oestradiol, achieving adsorption capacities of up to 56.67 mg g−1. Further validation in real environmental samples highlights the polymer's practical applicability, showing substantial removal rates even under complex matrix conditions and bringing hope for effective water purification solutions. Remarkably, polyPhOx retains high adsorption performance after 10 cycles, underscoring its potential for sustainable and cost‐effective water purification. This study not only introduces a promising material for environmental remediation but also demonstrates its robustness and reusability, paving the way for advanced wastewater treatment solutions targeting persistent pharmaceutical pollutants.

Promoting elemental mercury immobilization performance from smelting flue gas over a wide temperature range via cobalt-doped copper sulfide adsorbents

Copper sulfide (CuS) sorbent exhibits great potential for gaseous elemental mercury (Hg0) decontamination, but it still suffers from a narrow operating temperature. Therefore, designing advanced CuS sorbents that have a high activity level for capturing Hg0 and thermal stability at a high temperature range is challenging. Herein, we propose a metal doping strategy to fabricate a bimetallic sulfide adsorbent. Benefiting the unique structure and composition, a mesoporous structure and an abundance of unsaturated sulfur sites ensure that CuxCo(1–x)Sy provides a desirable level of adsorption for Hg0. The experimental results indicate the optimum Co doping mass concentration of 5 %. The Cu0.95Co0.05Sy not only performs satisfactory Hg0 adsorption at elevated temperatures (Hg0 average adsorption efficiency of over 97.3 %, Hg0 average adsorption rate of over 2.7 μg/g/min), but also presents an exciting regeneration and recycle performance (a Hg0 adsorption efficiency of over 94 % after 10 cycles). The adsorption capacity of Cu0.95Co0.05Sy at the breakthrough threshold of 25 % reaches 5.22 mg/g, surpassing most of metal sulfide sorbents for Hg0 immobilization at 150 °C. As far as Hg0 adsorption is concerned, the composition of typical smelting flue gases has almost no effect. According to further studies, unsaturated coordination short-chain sulfur (S22−) sites are essential for adsorption of Hg0 and are capable of directly forming α-HgS from Hg0. In both the contrast experiment and density functional theory calculations, the cobalt doping strategy enhances the thermal stability of the active S22− ligand and the Hg0 adsorption properties. This study not only provide a prospective adsorbent for Hg0 sequestration at wide temperature range, but also explores a method of utilizing gaseous contaminants for resource utilization.

Highly efficient adsorption and visible-LEDs-driven photodegradation of tetracycline over novel and green-synthesized p-BiOI/n-Bi2WO6 heterojunctions

Preparing bismuth compounds-based heterojunctions with superior redox capability has emerged as a promising strategy for environmental remediation. Herein, p-BiOI/n-Bi2WO6 heterojunctions were successfully obtained via a novel, facile, and green solvothermal method. The heterojunctions were synthesized using different mass ratios (1:2, 1:1, and 2:1) of BiOI (BI) and Bi2WO6 (BW), with 1:1 as the best ratio, which was decorated with silver nanoparticles (Ag-NPs) and nitrogen-doped graphene (NG) applying green methodologies. The as-prepared BI/BW heterojunctions were characterized by several techniques, and their adsorption capacity and photodegradation activity toward tetracycline (TC) under 19 W visible LEDs illumination were investigated. The capacity of pure BI, BW and BI/BW heterojunctions for adsorbing TC ranged from 14 to 68 mg/g; among the heterojunctions, Ag/1BI/1BW showed the highest TC adsorption capacity, 35 mg/g. Moreover, the photocatalytic tests revealed that the Ag/1BI/1BW exhibited the highest catalytic performance, achieving a TC percentage degradation of 81 % within 120 min. The low nominal power consumption of the LED-based photoreactor (0.0475 kWh) was significantly lower than that reported in the literature for using Xe or Hg lamps. In addition, catalyst dosage, initial TC concentration, and solution pH were investigated, demonstrating that they play important role in TC photodegradation. Scavenger assays determined that the degradation of TC using Ag/1BI/1BW proceeds mainly via superoxide radicals and holes, which agrees with the carrier transfer mechanism postulated for this heterojunction. TOC analysis revealed that the efficiency of Ag/1BI/1BW was 63 %, and reuse tests confirmed its high performance even after three cycles. This research provides new insights into the design of high-performance heterojunctions for water treatment.

Mesoporous TiO2@nitrogen-doped carbon nanosheets implanted in flexible and robust chitosan membrane with dual-function for efficient adsorption of iodide and methyl orange from aqueous solution

Radioactive iodide (I−) and methyl orange (MO) are two leading pollutants in wastewater, posing significant health risks. Crosslinked chitosan membranes (CCM) combined with TiO2@nitrogen-doped carbon nanosheets (CCM/TiO2@NC) were prepared as efficient I− and MO adsorbents in wastewater. These membranes leverage multiple interactions between I−/MO and functional groups (−NH2, nitrogen-doped carbon, and TiO2) within the membrane. As expected, CCM/TiO2@NC exhibited high I− removal efficiencies of nearly 82 % across a wide pH range (pH 3 − 11) and an exceptional MO removal efficiency of 96.1 % at a neutral condition. The adsorption behaviors followed the Langmuir isotherm and pseudo-second order kinetic model for both species, achieving maximum adsorption capacities of 1.383 mmol/g (175.6 mg/g) for I− and 661.4 mg/g for MO, respectively. Additionally, CCM/TiO2@NC maintained a high absorption efficiency for both I− and MO through five regeneration cycles. The I− adsorption mechanism of CCM/TiO2@NC involves electrostatic attraction, anion-π interaction, and hydrogen bonding, while MO adsorption involves electrostatic attraction, n/π-π interactions, and hydrogen bonding. This study offers feasible guidance on developing chitosan/nanomaterial composites as promising adsorbents for removing I− and MO from wastewater.

Novel bamboo-derived composites for the efficient adsorption of a methylene blue pollutant

Novel bamboo-derived composites for the efficient adsorption of a methylene blue pollutant

Efficient adsorption of flavonoids on amino-functionalized ZIF-8/chitosan aerogels

Covalent organic structures (MOFs), known for their exceptional properties in separation and purification, have garnered significant attention. However, applying MOF-based adsorbents in complex flavonoid separation scenarios remains challenging. In this study, we successfully synthesized adsorbent materials capable of efficiently adsorbing flavonoids using a vacuum freeze-drying method. The materials were derived from a cross-linked chitosan aerogel functionalized with amino-substituted zeolite imidazolium ester skeleton (ZIF-8). The ZIF-8-NH2, synthesized via in situ substitution of 2-aminobenzimidazole within the ZIF-8 framework, exhibits a smaller pore size than mono ligand ZIF-8. Due to its synergistic interaction with chitosan's biocompatibility and porous structure, the aerogel material (ZIF-8-NH2/CS) exhibited outstanding adsorption capacities (183.37 mg/g, 226.34 mg/g, and 187.16 mg/g) in standard solutions (T = 318 K, rpm = 200) of luteolin, quercetin, and rutin, along with high adsorption rates (71.3 ± 2.3 %, 72.4 ± 1.4 %, and 70.7 ± 3.5 %). And showed rapid adsorption in the first 60 min. After 5 cycles, the adsorption capacity of ZIF-8-NH2/CS aerogel remained at 80.5 % of the adsorption capacity of the initial cycle, and therefore, ZIF-8-NH2/CS aerogel has a good potential for reusability. Additionally, the adsorption process adhered to pseudo-first-order and pseudo-second-order kinetic models, alongside Langmuir and Freundlich isothermal adsorption models. This study introduces novel ideas and methods for the extraction and separation of flavonoids. Furthermore, the developed ZIF-8-NH2/CS aerogels with amino functionality hold promise for diverse applications in separating and purifying bioactive substances.

Highly efficient adsorption and removal of phthalate esters by polymers of intrinsic microporosity

In recent years, phthalate esters (PAEs) have been found to be endocrine disruptors that pose a serious safety threat to human health. Currently, adsorption is one of the most efficient technologies to remove PAEs, and the development of adsorbent materials that combine high adsorption capacity and short equilibrium time is a challenging problem. In this study, PIM-1, a typical representative of polymers of intrinsic microporosity (PIMs), was prepared through three methods and first used as adsorbents for PAEs removal. PIM-1 prepared under high temperature (HT-PIM-1) exhibited a high capacity of 787mg/g for dibutyl phthalate (DBP), a prevalent PAE in water, which is significantly higher than most reported adsorbents. Furthermore, more than 90.0% of the equilibrium adsorption capacity can be reached within 30mins. In addition, the adsorption of DBP could be inhibited by ethanol due to the enhanced interaction between DBP and ethanol, which could be revealed by molecular simulation. The adsorption mechanism of PAEs on PIM-1 mainly included hydrophobic interactions, π-π interactions, together with the size matching between PAEs and hierarchical pores of PIM-1. This study provides an idea for the application of PIMs for PAEs removal with high adsorption capacity and high efficiency. Environmental ImplicationPhthalate esters (PAEs) are emerging pollutants that pose a significant threat to public health and safety. They have been detected not only in environmental water but also in alcoholic beverages. Adsorption is widely preferred for removing PAEs, and the adsorption of PAEs in alcoholic solutions is a more challenging process compared to pure water. In this study, PIM-1 with o-phenyl groups similar to PAEs were first used as adsorbents for PAEs and demonstrated a remarkable adsorption capacity in both water (787mg/g) and alcoholic solutions (398mg/g) within a short period, surpassing the performance of commercial adsorbents.

Enhanced removal of polystyrene microplastics by three-dimensional flower-like layered double oxide: Behavior and mechanism insight

Microplastics (MPs) as emerging pollutants are becoming a global threat due to their potential environmental and human health risks. Conventional adsorbents used for MPs elimination tend to be unstable in acid or alkaline conditions, leading to inferior removal efficiency. Herein, a robust and efficient adsorbent, i.e., hierarchically structural ZnAl-layered double oxides (H-ZnAl-LDO), was elaborately developed via a one-step calcination strategy. This process created a flower-like porous structure supported by ZnAl2O4 spinel and ZnO. H-ZnAl-LDO exhibited an outstanding adsorption ability for polystyrene (PS, typical MPs) across a wide pH range (3−11), achieving a removal efficiency of 85–100 % and a maximum adsorption capacity of 91.17 mg/g. The intraparticle diffusion model combined with SEM analysis revealed that pore filling contributed to PS removal. Evidence from in FT-IR and XPS spectra and zeta potential substantiated the PS removal was dominated by electrostatic interaction, hydrogen bonding, and complexation. In addition, given the over 90 % PS removal efficiency from natural water, H-ZnAl-LDO demonstrated high potential in practical applications. This study provides a promising adsorbent for removing microplastics in both acidic and alkaline environments and broadens scope of applications for LDO.

Efficiency of heat-treated sepiolite in the adsorption of Cd, Zn, and Co from aqueous solutions: A low-cost approach for wastewater treatment

This study investigated the adsorption of Cd, Co, and Zn ions onto unmodified and heat-treated sepiolite, focusing on the effect of contact time, initial pH, and heat pretreatments. Kinetic experiments were conducted in triplicate, and equilibrium experiments indicated that Co2+ had the highest adsorption preference, followed by Zn2+ and Cd2+. The adsorption efficiency for Co2+ significantly increased with higher initial pH, whereas Zn2+ and Cd2+ showed optimal adsorption at lower pH levels. Heat-treated sepiolite at 250 ℃ exhibited a higher surface area and adsorption capacity in comparison with unmodified and 150 ℃-treated sepiolite, which indicated the importance of heat pretreatment. The pseudo-second-order kinetic model better described the adsorption process, and it was confirmed chemisorption as the rate-limiting step. By increasing the contact time, adsorption rates enhanced, with equilibrium achieved within 480 min for all systems. Higher initial solute concentrations led to an increase in adsorption processes, with Co ions consistently showing higher adsorption efficiency in competitive multi-ionic solutions. Adsorption percentages varied with pH and thermal treatment, indicating the importance of these parameters in optimizing sepiolite’s adsorption capacity for heavy metal removal.

The research progress of bio char in environmental pollution and treatment

In recent years, various forms of environmental pollution have become increasingly severe, leading to a dangerous state in the atmosphere, water, and soil environments. This poses a threat to people's daily lives and has sparked widespread concern in society. Concurrently, bio char, a novel carbon material known for its large specific surface area, porosity, affordability, and excellent adsorption capabilities, has garnered attention. The incremental development and utilization of bio char have positioned it as a promising contender in sewage treatment, air pollution control, soil pollution treatment and other pollutant adsorption processes. This paper provides a comprehensive review of the preparation of bio char, its current research status, and the factors influencing its adsorption efficiency through an extensive literature survey.

Regulating the Surface State of Carbon Dots as Ultrahigh-Capacity Adsorbents for Water Treatment.

Adsorption is one of the most widely researched and highly effective methods for mitigating the environmental threat posed by recalcitrant dyes in aqueous solutions. This paper presents a solvent-free synthesis method for the rapid and large-scale production of nitrogen (N) and phosphorus (P) co-doped carbon dots (N, P-CDs) which possess specific surface states and outstanding dye adsorption properties. Compared to the undoped CDs, the N, P-CDs not only exhibit a higher yield of solid-state luminescence but also endow them with the efficient adsorption and removal of Congo red (CR) from water. Due to the synergistic effects of π-π stacking, hydrogen bonding and electrostatic attraction, the N, P-CDs exhibit an ultra-high adsorption capacity (3118.87mgg-1) and a removal efficiency (97.4%, at 500mgL-1) for CR, and also display excellent selective adsorption in both single-dye and dual-dye systems. This method offers a rational strategy for synthesizing novel CDs-based adsorbents for CR, which provides a demonstration for future dye adsorption studies and practical wastewater treatment applications of CDs.

Optimizing excited state adsorption and carrier dynamics of metal doped zinc oxide by p-d orbital modulation for efficient reverse saturation absorption

Doping metals can regulate the excited state adsorption and carrier transport efficiency of ZnO through p-d orbital coupling thereby improving its nonlinear performance. Herein, the thin film coatings consisting of ZnO, and M-ZnO (M=Al, Sn, Mg) were synthesized using the magnetron sputtering technique. ZnO exhibited the granular/stick structure, while the metal dopant atoms (M) were incorporated into the ZnO lattice, resulting in a homogeneous distribution. Photoluminescence spectroscopy reveals the quenched defect emission intensity, indicating a decrease in the rate of photo-induced electron-hole pair complexation. Mg exhibits an optimized effect to promote the saturation absorption of ZnO, resulting in the enhancement of the nonlinear absorption (NLA) coefficients for M-ZnO films. Al-ZnO and Sn-ZnO films exhibit reverse saturation absorption. Theoretical simulation shows that the additions of transition metal atoms favor the electron transfer through p-d orbital modulation of ZnO. The p-d hybridization causes the metal-d orbitals to cross the Fermi level and form an electron transport channel, thereby enhancing the excited state absorption, and effectively controlling the NLA process and mechanism. The excited state absorption of the M-ZnO films significantly rises. This research demonstrates that the optimization of excited state absorption through p-d orbital modulation is a highly effective strategy for the development of efficient and superior nonlinear optical absorbers.

Corn stalk decorated with magnetic graphene oxide as an efficient adsorbent for the removal of cationic dye from wastewater

In this study, an in situ immersion loading method is employed to introduce graphene oxide (GO) nanosheets and hollow copper ferrite nanospheres into the ordered porous structure of alkali-activated corn stalk (CS). This approach facilitates the construction of a novel magnetic three-dimensional composite sponge (GO/CS/CuFe2O4) utilized for the efficient removal of methylene blue (MB) and malachite green (MG) dyes from wastewater samples. In this hybrid adsorbent, the stacking of GO nanosheets is inhibited due to the ordered porous structure of CS, based on which GO nanosheets are well immobilized and dispersed. In addition, the hollow CuFe2O4 nanospheres and GO nanosheets support each other, further reducing the accumulation of GO, and increasing the specific surface area of the adsorbent. The engineered morphology of GO/CS/CuFe2O4 sponges supports the maximum exposure of the active adsorption sites to the dye solution, promoting the adsorption process. Microscopy and surface analyses show that GO/CS/CuFe2O4 sponges have a rich pore structure with the specific surface area of 289.85 m2·g−1, more than 17 times higher than that of CS, significantly improving their adsorption performance for MB and MG. The maximum adsorption capacity of GO/CS/CuFe2O4 for MB and MG is as high as 243.65 and 231.53 mg/g, respectively, superior to those of many other biomass-based adsorbents. The dye adsorption performance of GO/CS/CuFe2O4 can be well described by the Langmuir adsorption isotherm and pseudo-second-order kinetic model, suggesting the existence of strong monolayer chemisorption. The FTIR and X-ray photoelectron spectroscopy (XPS) analyses show that the dye removal mechanisms observed mainly includ π-π interactions, hydrogen bonding, electrostatic interactions and pore filling. In addition, GO/CS/CuFe2O4 sponges exhibit an excellent magnetic behavior (Ms = 49.52 emu/g), enabling the adsorbent to be recycled by the application of a magnetic field. The adsorption capacities of the adsorbent for MB and MG remain 88.6 % and 90.2 % of the initial adsorption capacity, respectively, even after 10 regeneration cycles, showing its excellent reusability performance. Finally, GO/CS/CuFe2O4 is applied for the removal of MB and MG from real aqueous environments comprising the seawater, tap water and wastewater treatment plant effluent, and the removal rates are observed to be over 90 % of that achieved in deionized water. This study provides new concepts for the sustainable utilization of agricultural waste and natural structure of plants to purify dye containing wastewater.

Transferring red mud to efficient adsorbent for the adsorption and immobilization of Ni(Ⅱ) from aqueous solution

Red mud, a solid waste produced in large quantities, possesses a high specific surface area and is rich in metal oxides, making it a promising material for adsorbent preparation. However, its practical application is constrained by its relatively low adsorption capacity and the potential environmental risks it poses. This study focused on the preparation of modified red mud (MRM) with enhanced adsorption performance for Ni2+ using a hydrothermal method involving sodium hydroxide and colloidal silica. The maximum adsorption capacity of MRM for Ni2+ reached 8.22 mmol·g–1, a substantial improvement compared to raw red mud (0.28 mmol·g–1) and sulfuric acid-activated red mud (0.46 mmol·g–1). The pseudo-second-order kinetic and Langmuir isotherm models accurately described the monolayer chemical adsorption process of Ni2+ on MRM. Additionally, leaching tests with simulated rainwater demonstrated that Ni-loaded MRM exhibited high stability, suggesting its potential for safe stockpiling or repurposing, such as in construction materials. Sequential extraction, XRD, FT-IR, and XPS results revealed that cation exchange was the primary mechanism in the adsorption process, with Ni2+ being immobilized within the zeolite framework structure of MRM, contributing to its strong adsorption stability. Inner-sphere complex formation also played a role in Ni2+ adsorption. In conclusion, this method offers an effective approach to both red mud utilization and heavy metal removal from wastewater, presenting a practical solution for waste management through resource recovery and environmental remediation.

Adsorption and dersorption of lead using synthetic hydroxyapatite material

The adsorption of Pb2+ ions in solution by synthetic hydroxyapatite material has been researched. Investigations were conducted into the effects of adsorption time, adsorbent mass, solution pH, and Pb2+ ion concentration. The material's adsorption efficiency to Pb2+ can reach 98.7%. Two adsorption isotherm models, Freunlich and Langmuir, were used to evaluate adsorption isotherms. The pseudo-first-order and pseudo-second-order adsorption kinetic models were used to assess the adsorption process's kinetics. Using the electrolysis approach, Pb2+ ions were successfully desorbed from the adsorbed HAp material while recovering metallic Pb on the cathode surface. Pb recovery efficiency can be as high as 93.84%. After desorption, the HAp material retains its original characteristics and still can adsorb Pb2+ ions with a high efficiency of 95.96%.

Evaluation, optimization study, and life cycle assessment of novel eco-friendly PVA-based nanocomposite hydrogel adsorbents for methylene blue and paracetamol removal

In this study, an eco-friendly and novel hydrogel based on a crosslinked polyvinyl alcohol (PVA), iota carrageenan (IC) and polyvinylpyrrolidone (PVP) scaffold, containing a large amount (10–50 wt%) of nanoscale palm fronds (NPF) as additives, for water purification was demonstrated. A life cycle assessment (LCA) findings on NPF as biomass waste incorporated into PVA_PVP_IC polymer matrix was presented, and the results highlight the necessity of focused actions to reduce environmental impact and support the palm waste utilization in a sustainable manner. The multicomponent nanocomposite hydrogels were examined as adsorbents in a system work in batches for methylene blue (MB) and paracetamol (PCT) removal. The results show that, the presence of NPF, which dispersed in the hydrogel PVA_PVP_IC scaffolds containing both covalent and non-covalent cross-linking bonds, greatly enhanced the MB and PCT adsorption efficiency. A response surface methodology (RSM) model was used to find the best operating parameters of contaminant adsorption, including time, adsorbent dose, and starting concentration of pollutants. By using this statistical model, it was found that the optimal conditions for the adsorption reaction to achieve the complete removal of MB are 66.7 h adsorption time duration, 98.5 mg L−1 starting concentration, and an adsorbent dose of 5.9 mg, while for the complete removal of PCT, it is 57.6 h adsorption time duration, 80 mg L−1 starting concentration, and an adsorbent dose of 6 mg. The reusability of the nanocomposite hydrogels were tested for 5 cycles, all showed high adsorption capacity, indicating the potential for practical application of this nanocomposite hydrogel system. This study indicates that the prepared nanocomposite hydrogel raises the standard used for treatment of wastewater and also gives a solution to protect the environment and mitigate global warming.