Ions In Wastewater Research Articles

Preparation of corn starch/acrylic acid/itaconic acid ion exchange hydrogel and its adsorption properties for copper and lead ions in wastewater

In this study, corn starch/acrylic acid/ itaconic acid (CS/AA/IA) hydrogel was prepared by solution polymerization, and then alkaline washed with sodium hydroxide solution to form corn starch/acrylic acid/ itaconic acid (CS/AA/IA) ion exchange hydrogel for the adsorption of copper and lead ions in aqueous solution. The structure and morphology of the hydrogel were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of contact time, initial concentration, temperature, pH, coexisting ions and different water types on the adsorption of Pb2+ and Cu2+ were analyzed by batch adsorption experiments. The CS/AA/IA ion exchange hydrogel reached adsorption equilibrium within 40 min. The maximum adsorption capacities of Pb2+ and Cu2+ fitted by the Langmuir isothermal adsorption model were 869.56 mg/g and 699.31 mg/g, respectively. After five adsorption-desorption cycles, the adsorption capacity of the hydrogel for Pb2+ and Cu2+ remained at 95%. The synthesis method maximized the conversion of –COOH in the hydrogel into the active group –COONa, forming a highly efficient adsorption hydrogel with ion exchange as the main effect. The CS/AA/IA ion exchange hydrogel exhibits high adsorption capacity, fast adsorption efficiency and remarkable regeneration property, and shows potential applications in the field of water treatment.

Thermally modified fish scale as potential adsorbents for the remediation of nitrite, nitrate and ammonium ions in wastewater

Thermally modified fish scale as potential adsorbents for the remediation of nitrite, nitrate and ammonium ions in wastewater

Activated carbon based paste electrodes for the simultaneous and effective detection of divalent cadmium and lead ions in wastewater

ABSTRACT Heavy metals (HM) have gained significant attention in terms of regular monitoring and detection owing to their toxicity, non-biodegradability, and persistence. Current techniques for detecting HM are expensive, cumbersome, and require sophisticated instruments and skilled labour. Hence, developing cheap, rapid, energy-efficient, and accurate sensors is imperative and electrochemical techniques have emerged as promising tools. The current study involves the fabrication of an electrochemical sensor for the concurrent detection of lead (Pb2+) and cadmium (Cd2+) ions using modified carbon paste electrodes (mCPE). Activated carbon (AC) with a BET surface area of 1118 m2 g−1 was obtained by chemical activation and thermal treatment of the waste rubberwood sawdust. AC-Graphite, AC-Reduced Graphene Oxide (RGO), and AC-RGO-Chitosan were the types of mCPEs that were utilised. The electrochemical behaviours and effects of pH, concentration, and scan rate were studied using Cyclic voltammetry (CV). Studies on detection were conducted using CV and linear sweep voltammetry. Although all the 3 mCPEs detected Cd2+ and Pb2+ in the simulated wastewater, the CPE with RGO and AC could detect Cd2+ as low as 10.91 µg L−1 and Pb2+ as low as 14.01 µg L−1. The work explored the possibility of using AC as a potential sustainable substitute for graphite in CPE.

Removal of Hexavalent Chromium from Water by Chitosan-Enhanced Ultrafiltration

Polymer-enhanced ultrafiltration has gained increasing attention as a selective separation process to remove small solutes, such as metal ions, from water or wastewater. Hexavalent chromium Cr(VI) is one of the metal ions in wastewater that has received considerable attention because of its toxicity. Chitosan was used in this study as the polymer to bind Cr(VI) to enhance its removal by ultrafiltration. The effects of chitosan-to-Cr(VI) ratio on Cr(VI) rejection and permeate flux were investigated. In addition, the fouling tendency was evaluated. Results showed that the addition of chitosan with a mass ratio of 12.5 increased the Cr (VI) rejection from 28% to 75% with a slight reduction in permeate flux from 12.5 L.m−2.h−1 to 9.3 L.m−2.h−1. Moreover, the reduced flux after 100 min of operation could be recovered using the backwash procedure by 89% compared to the initial flux.

Dual-Functional Ln-OFs for Efficient Luminescence Sensing and Photoreduction of Cr(VI) without Additional Photosensitizers and Cocatalysts

Six isostructural stable lanthanide metal–organic Frameworks (Ln-OFs), namely, [Ln(ADBA)(HCOO)(DMF)] (Ln = Sm(1), Tb(2), Dy(3), Ho(4), Er(5), Eu(6), H2ADBA = 4,4′-(anthracene-9,10-diyl)dibenzoate, DMF = N,N-dimethylformamide), have been successfully obtained by the solvothermal method based on an aromatic carboxylic acid ligand H2ADBA. 1–6 have a similar three dimensional (3D) network structure with pts topology based on dinuclear metallic clusters {Ln2}. 1–6 all have excellent chemical and thermal stabilities, which is beneficial to carrying out fluorescence sensing and achieving catalytic reactions. 1–6 show admirable fluorescent properties in aqueous solution and can quickly and efficiently detect Fe3+, Cr2O72–, and nitrofurazone (NZF) with high selectivity and excellent sensitivity. Remarkably, upon completion of detection, the Cr2O72– ion in wastewater can be reduced into Cr3+ by photocatalyst 1, which is ascribed to its broad-range visible-light absorption and recyclable stability. During the reduction process, ethanol is an optimal hole scavenger; 1 shows an excellent convert efficiency (99%), a high rate constant (k) of 0.066 min–1, and a high Cr(VI) reduction rate of 0.158 mgCr(VI)·g–1cata·min–1 at pH = 2. Furthermore, photocatalyst 1 can be reused for three cycles without significant loss of catalytic activity. Until now, it is the first example to report that the photocatalytic reduction of Cr(VI) is achieved only by using 3D rare earth MOFs without additional photosensitizers and cocatalysts. The reasonable mechanisms of luminescence sensing and photocatalytic reaction were also investigated systematically via indispensable testing technologies and theoretical simulated calculation.

Application of the metal ions as potential population biomarkers for wastewater-based epidemiology: estimating tobacco consumption in Southern China.

Wastewater-based epidemiology (WBE) is an objective approach for the estimation of population-level exposure to a wide range of substances, in which the use of a population biomarker (PB) could significantly reduce back-calculation errors. Although some endogenous or exogenous compounds such as cotinine and other hormones have been developed as PBs, more PBs still need to be identified and evaluated. This study aimed to propose a novel method to estimate population parameters from the mass load of metal ion biomarkers in wastewater, and estimate the consumption of tobacco in 24 cities in Southern China using the developed method. Daily wastewater samples were collected from 234 wastewater treatment plants (WWTPs) in 24 cities in Southern China. Atomic absorption spectroscopy (AAS) was applied to determine the concentrations of common health-related metal ions in wastewater, including sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), iron (Fe), and zinc (Zn), and compared them with the daily mass load of cotinine corresponding to catchment populations. The concentrations of cotinine in wastewater samples were measured using liquid chromatography-tandem mass spectrometry. There were clear and strong correlations between the target metal ion equivalent population and census data. The correlation coefficients (R) were RK = 0.78, RNa = 0.66, RCa = 0.81, RMg = 0.77, and RFe = 0.69, at p < 0.01 and R2 > 0.6. Subsequently, the combination of WBE and metal ion PBs was used to estimate tobacco consumption. Daily consumption of nicotine was estimated to be approximately 1.76 ± 1.19mg/d/capita, equivalent to an average of 13.0 ± 8.75 cigarettes/d being consumed by smokers. The data on tobacco consumption in this study were consistent with those in traditional surveys in Southern China. The metal ion potassium is an appropriate PB for reflecting the real-time population and could be used to evaluate the tobacco consumption in WBE study.

Yeast biomass ornamented macro-hierarchical chitin nanofiber aerogel for enhanced adsorption of cadmium(II) ions

There is an urgent need to develop sustainable, renewable, and environment-friendly adsorbents to rectify heavy metals from water. In the current study, a green hybrid aerogel was prepared by immobilizing yeast on chitin nanofibers in the presence of a chitosan interacting substrate. A cryo-freezing technique was employed to construct a 3D honeycomb architecture comprising the hybrid aerogel with excellent reversible compressibility and abundant water transportation pathways for the accelerated diffusion of Cadmium(II) (Cd(II)) solution. This 3D hybrid aerogel structure offered copious binding sites to accelerate the Cd(II) adsorption. Moreover, the addition of yeast biomass amplified the adsorption capacity and reversible wet compression of hybrid aerogel. The monolayer chemisorption mechanism explored by Langmuir and pseudo-second-order kinetic exhibited a maximum adsorption capacity of 127.5 mg/g. The hybrid aerogel demonstrated higher compatibility for Cd(II) ions as compared to the other coexisted ions in wastewater and manifested a better regeneration potential following four consecutive sorption-desorption cycles. Complexation, electrostatic attraction, ion-exchange and pore entrapment were perhaps major mechanisms involved in the removal of Cd(II) revealed by XPS and FT-IR. This study unveiled a novel avenue for efficient green-synthesized hybrid aerogel that may be sustainably used as an excellent purifying agent for Cd(II) removal from wastewater.

Fabricating hydroxyapatite functionalized biochar composite using steel slag and Hami melon peel for Pb(II) and Cd(II) removal

With rising global concerns about the discharge of large volumes of waste materials derived from industrial manufacture and human life, methods for utilizing waste materials have been greatly developed. In this study, an ingenious hydroxyapatite (Hap) functionalized hierarchical porous biochar (HB) composite is fabricated using a filtrate rich in Ca2+ ions after steel slag reuse and spent Hami melon peel as raw materials. Microstructural analyses indicate that Hap nanoparticles are loaded on HB with hierarchical pores produced from a pyrolysis process of Hami melon peel. A series of HB-Hap materials by tuning HB addition amount (0.5, 1, and 2 g) can be obtained through a coprecipitation process. As a case study, HB-0.5Hap exhibits high specific surface area of 66.92 m2/g and high-efficiency removal performance for Pb(II) and Cd(II) ions in wastewater. The maximum adsorption capacities of HB-0.5Hap are 134.4 (Pb(II)) and 60.4 (Cd(II)) mg/g, which are 1.77 and 1.23 times higher than that of pure HB, respectively. It is attributed to a synergistic mechanism involving ion exchange, chemical precipitation, surface complexation, and cation-π interaction. According to a semi-quantitative calculation, ion exchange plays a major role in the removal of Pb(II) (78.61%, the relative contribution of ion exchange mechanism) and Cd(II) (77.77%). This study demonstrates a facile, economical, and sustainable strategy for the value-added utilization of steel slag and spent Hami melon peel, which can be critical in solving environmental problems.

Preparation of Nanofiber Affinity Membrane by Electrospinning and its Application in Metal Ion Recovery

With the rapid development of modern industry and agriculture, metal ion wastewater is being discharged unchecked, resulting in serious pollution of water and soil resources systems. At the same time, the unrestrained exploitation and waste in recent decades have led to the gradual depletion of metal ion mineral resources. Among them, rare earth metal ions, as national strategic resources, have application value in many high-tech fields. Therefore, how to effectively separate and recycle metal ions in wastewater is one of the research hotspots. Adsorption separation technology has the advantages of high efficiency, low cost, simple operation and equipment, and low energy consumption, and is widely used in metal ion wastewater treatment.

Adsorption and Removal of Cr6+, Cu2+, Pb2+, and Zn2+ from Aqueous Solution by Magnetic Nano-Chitosan.

Magnetic nano-chitosan (MNC) was prepared and characterized. The kinetics, thermodynamics, and influencing factors of the adsorption of Cr6+, Cu2+, Pb2+, and Zn2+, as well as their competitive adsorption onto MNC in aqueous solution, were studied. The results showed that the adsorption kinetics and thermodynamics of Cr6+, Cu2+, Pb2+, and Zn2+ were well described by the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, indicating that the adsorption was mainly chemical adsorption and endothermic. Increasing the dosage of MNC, the equilibrium adsorption capacity (qe) of Cr6+, Cu2+, Pb2+, and Zn2+ decreased; their removal rate (η) increased. With the increase in the solution's pH, the qe and η of Cr6+ first increased and then decreased; the qe and η of Cu2+, Pb2+, and Zn2+ increased. With the increase in the metal ion initial concentration, the qe increased; the η of Cr6+, Cu2+, and Zn2+ decreased, while the η of Pb2+ increased first and then decreased. Temperature had a weak influence on the qe of Cr6+ and Pb2+, while it had a strong influence on Cu2+ and Zn2+, the qe and η were greater when the temperature was higher, and the adsorption was spontaneous and endothermic. The qe and η of Cu2+, Pb2+, and Zn2+ decreased in the presence of co-existing ions. The influences among metal ions existed in a binary and ternary ion system. The current study's results provide a theoretical support for the simultaneous treatment of harmful metal ions in wastewater by MNC.

Activation of Durian Skin Biomass with H2SO4 Activator on the Absorption of Lead from its Solution

Research has been carried out on the bioabsorption of lead (Pb) using durian skin biomass (Durio zibethinus) which has been activated using an H2SO4 activator. The durian skin sample used was durian skin from Central Sulawesi. The processing technique to remove lead (Pb) from liquid waste was carried out by an adsorption process. The adsorption process is an effective purification and separation technique used in industry because it is more economical and simple in treating wastewater and is a technique that is often used to reduce metal ions in wastewater. This study aims to determine the mass and contact time of the adsorption of Pb by durian skin biomass. Determination of the adsorbed metal used atomic absorption spectrophotometry (AAS). The results obtained showed that the optimal Pb ion adsorption occurred at a weight of 2.5 grams with an absorption capacity of 99.94 %. While the optimal Pb ion adsorption occurred at a contact time of 40 minutes with an absorption capacity of 99.94 %

Highly fluorescent composite of boron nitride quantum dots decorated on cellulose nanofibers for detection and removal of Hg(II) ions from waste water

To address the challenge of heavy-metal ions in wastewater, boron nitride quantum dots (BNQDs) were synthesized in-situ on rice straw derived cellulose nanofibers (CNFs) as substrate. The composite system exhibited strong hydrophilic-hydrophobic interactions, as corroborated by FTIR, integrated the extraordinary fluorescence properties of BNQDs with fibrous-network of CNFs (BNQD@CNFs) yielding a surface of 35.147 m2 g−1 of luminescent fibers. Morphological studies revealed uniform distribution of BNQDs on CNFs due to hydrogen bonding, according high thermal stability with peak degradation occurring at 347.7 °C and quantum yield of 0.45. The nitrogen-rich surface of BNQD@CNFs exhibited strong affinity for Hg(II), quenching the fluorescence intensity due to combined inner-filter effect and photo-induced electron transfer. The limit of detection (LOD) and limit of quantification (LOQ) were 4.889 nM and 11.1 5 nM, respectively. BNQD@CNFs concomitantly exhibited adsorption of Hg(II) owing to strong electrostatic interactions, confirmed by X-ray photon spectroscopy. Presence of polar BN bonds favoured 96 % removal of Hg(II) at 10 mg L−1 with maximum adsorption capacity of 314.5 mg/ g. Parametric studies corresponded to pseudo-second order kinetics and Langmuir isotherm with R2 ≈ 0.99. BNQD@CNFs exhibited recovery rate between 101.3 %–111 % for real water samples and recyclability upto 5 cycles, demonstrating high potential in wastewater remediation.

Cost-Effective Preparation of Gold Tailing-Based Aerogels for Efficient Adsorption of Copper Ions from Wastewater

Water pollution caused by heavy metal ions has attracted worldwide attention. In this work, gold tailings were used as raw materials and the sol–gel method combined with the atmospheric pressure drying method were used to achieve the low-cost preparation of a silica aerogel. (3-Aminopropyl) triethoxysilane (APTES), ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), and chitosan were used to modify the silica aerogel, which was then used as an adsorbent for the adsorption of copper ions in wastewater. The adsorbent type, adsorption time, copper ion concentration, and pH value were investigated as variables to explore the best adsorption conditions. The adsorption mechanism was also elaborated on. The crystal structure, surface morphology, surface functional groups, chemical composition, and specific surface area of the aerogels and the modified aerogels were characterized by various physiochemical characterizations such as XRD, SEM, FT-IR, XRF, and BET. The results showed that the prepared silica aerogel contained 91.1% SiO2, mainly amorphous SiO2, and amino and carboxyl groups. Other functional groups were successfully grafted onto the silica aerogels. The original silica aerogels and modified silica aerogels had a large specific surface area, total pore volume, and pore diameter. When copper ions were adsorbed by the chitosan-modified silica aerogels, the adsorption capacity of the copper ions was the highest (33.51 mg/g) under the conditions of a copper ion concentration of 100 mg/L, a pH value of 7, and an adsorption time of 2 h. The adsorption of Cu2+ was mainly due to the ion exchange and electrostatic gravity.

Efficient three-step strategy for reduction recovery of high purity uranium oxide from nuclear wastewater

Resource utilization of uranium from the nuclear wastewater is of significance, and the facile strategy to recover high purity uranium oxide directly from wastewater is urgent to develop. Herein, a three-step uranium oxide reduction recovery process (URRP), that is integrated solid–liquid separation (SLS) and electrochemical purification (EP) together with solid-phase uranium re-recovery (SUR), is designed and applied for uranium reduction and purification. The SEM and ICP results were used to determine the carbonate system as the optimal separation system and the Ti electrode as the optimal electrochemical purification electrode. The single electron transfer process of uranyl ions in carbonate was established using cyclic voltammetry. Such three-step recovery process achieves a high-efficient recovery of uranium with a purity of over 99.9% in complex wastewater systems, and an improved return rate of uranium as high as 98.6%. Furthermore, the concentration of metal ions in wastewater is reduced to the standard set by the World Health Organization. Such a URRP offers a very promising solution for the treatment of wastewater and the recovery of high purity uranium.

Effective adsorption of heavy metal ions in water by sulfhydryl modified nano titanium dioxide.

Background: The monitoring and removal of heavy metal ions in wastewater will effectively improve the quality of water and promote the green and sustainable development of ecological environment. Using more efficient adsorption materials and more accurate detection means to treat heavy metal ions in water has always been a research focus and target of researchers. Method: A novel titania nanomaterial was modified with sulfhydryl group (nano TiO2-SH) for detection and adsorption of heavy metal ions in water, and accurately characterize the adsorption process using Surface-Enhanced Raman Spectroscopy (SERS) and other effective testing methods. Results: The maximum adsorption efficiency of nano TiO2-SH for the Hg2+, Cd2+, Pb2+ three heavy metal ions reached 98.3%, 98.4% and 98.4% respectively. And more importantly, after five cycles of adsorption and desorption, the adsorption efficiency of nano TiO2-SH for these three metal ions is still above 96%. Conclusion: These results proved the nano TiO2-SH adsorbent has great potential in practical water pollution purification.

Process parameters and biological mechanism of efficient removal of Cd(II) ion from wastewater by a novel Bacillus subtilis TR1

The safe treatment of heavy metals in wastewater is directly related to the human health and social development. In this paper, a new biological strain has been isolated from electroplating wastewater, which can effectively remove metal ions in wastewater. The results of 16 S rDNA sequencing analysis and NCBI GenBank database comparison show that the strain belongs to a novel Bacillus genus and names Bacillus subtilis TR1 with the accession number of OL441606. The removal rate of Cd(II) reaches to 85.68% with the conditions of pH = 7, C0Cd(II) = 20 mg L−1, t = 48 h, m = 0.1 g, and T = 35 °C. The biological removal mechanism of Cd(II) is in-depth studied by FTIR and XRD combined with third-generation sequencing. The results indicate that Bacillus subtilis TR1 removes Cd(II) mainly through two synergistic pathways, namely, extracellular chemisorption and intracellular bioaccumulation: 1) The groups carried on the surface of the strain, such as –COOH, –NH, –OH and C–H, have good chemisorption properties for Cd(II) and easily form cadmium containing chelation (–COO–Cd(II), -N-Cd(II), etc.) with these groups. The appearance of TR1 strain changes from cylindrical to spherical after Cd(II) adsorption, which is due to the biotoxicity of Cd(II); 2) Cd(II) exchanges on the surface of TR1 strain with K and Na ions released from the intracellular cytoplasm and enters the cytoplasm under the transfer of biological transport medium. This part of Cd(II) is converted into its own components by anabolic enzymes and accumulates in the cytoplasm. These data provide a new biological agent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Biosorption and bioreduction of aqueous chromium (VI) by different Spirulina strains.

Spirulina has emerged as a promising microorganism for the treatment of industrial heavy metal ions in wastewater due to their simplicity of cultivation and harvesting, rich functional binding groups and high bioreductive activity during the uptake process. While the capacities of biosorption and bioreduction for heavy metal ions differs significantly among various algal strains. Therefore, the physiological characteristics were investigated to identify the different Spirulina strains and the chromium (VI) adsorption capacities of the algal strains were also evaluated. In this study, it was found that algal strains YCX2643 and CLQ1848 performed higher removal efficiency (86.5% and 83.7%) than other four Spirulina strains (59.4%, 56.3%, 65.6% and 66.5%, respectively). Moreover, the mechanisms of chromium (VI) ions binding and biotransformation in the Spirulina cell were scrutinize by FT-IR spectroscopy and scanning electron microscopy(SEM), and it indicated that the varieties of cellular components involved in high binding affinity may cause the higher biosorption and bioreduction of aqueous chromium (VI) in algal strains YCX2643 and CLQ1848, which could be used as promising biosorbents in the removing heavy metal pollutants from wastewaters.

2D/2D Transition‐Metal‐Sulfide Self‐Assembly Enables a Huge Tolerance to High Concentration Cr(VI) and a Prominent Photocatalytic Reduction Performance

AbstractTwo‐dimensional (2D) transition‐metal‐sulfides always suffer from poor optical absorption ability, serious photogenerated carrier recombination, and lack of tolerance to high concentration Cr(VI), which limit their wide applications. Herein, 2D MoS2 nanosheets are in situ grown on 2D 5 % Cu‐doped ZnIn2S4 nanosheets to fabricate self‐assembly via a two‐step solvothermal method. The incorporation of Cu broadens the optical response range of self‐assembly and introduces an acceptor trap level that changes the valence band allocation of ZnIn2S4 nanocrystals, which improves the separation and migration of photogenerated electron‐hole pairs. As a result, complete photoreduction of Cr(VI) is surprisingly achieved for 2D/2D self‐assembly MoS2/Cu−ZnIn2S4 in 4 min under visible light irradiation (λ≥400 nm) without sacrificing any agents. Moreover, this self‐assembly is further indicated to have a strikingly huge tolerance to high concentration Cr(VI) (250 mg ⋅ L−1), and the photoreduction activity of Cr(VI) is almost not disturbed by high concentration inorganic ions in wastewater. All these merits demonstrate that 2D/2D transition‐metal‐sulfide self‐assembly may find many practical applications in water cleaning and environmental remediation.

Eco-Friendly Polysaccharide-Based Synthesis of Nanostructured MgO: Application in the Removal of Cu2+ in Wastewater.

The present study described three synthesis routes using different natural polysaccharides as low-cost non-toxic fuels and complexing agents for obtaining MgO. Cassava starch, Aloe vera leaves (mainly acemannan) gel, and citric pectin powder were mixed with magnesium nitrate salt and calcined at 750 °C for 2 h. The samples were named according to the polysaccharide: cassava starch (MgO-St), citrus pectin (MgO-CP), and Aloe vera (MgO-Av). X-ray diffraction identified the formation of a monophasic periclase structure (FCC type) for the three samples. The N2 adsorption/desorption isotherms (B.E.T. method) showed an important difference in textural properties, with a higher pore volume (Vmax = 89.76 cc/g) and higher surface area (SA = 43.93 m2/g) obtained for MgO-St, followed by MgO-CP (Vmax = 11.01 cc/g; SA = 7.01 m2/g) and MgO-Av (Vmax = 6.44 cc/g; SA = 6.63 m2/g). These data were consistent with the porous appearance observed in SEM images. Porous solids are interesting as adsorbents for removing metallic and molecular ions from wastewater. The removal of copper ions from water was evaluated, and the experimental data at equilibrium were adjusted according to the Freundlich, Langmuir, and Temkin isotherms. According to the Langmuir model, the maximum adsorption capacity (qmax) was 6331.117, 5831.244, and 6726.623 mg·g-1 for the adsorbents MgO-St, MgO-Av, and MgO-CP, respectively. The results of the adsorption isotherms indicated that the synthesized magnesium oxides could be used to decrease the amount of Cu2+ ions in wastewater.

On the removal efficiency of copper ions in wastewater using calcined waste eggshells as natural adsorbents

Eggshells offer many advantages as adsorbents, such as affordability without special preparations other than pulverization and calcination. However, the manufacturing industry generally has a severe problem with high concentrations of heavy metals in wastewater. The purpose of this study was to use eggshell byproducts and calcined eggshell treatment for the adsorption of copper in an aqueous solution. The reaction time, metal concentration, adsorbent dose, temperature, and pH were evaluated using primary factors followed by the response surface method (RSM) to investigate the optimum conditions for eggshell byproducts and calcined eggshell adsorption treatment. The results of the one-factor-at-a-time experiment showed that the optimal adsorption rate was obtained from treatment at 24 h, 25 mg/L, 10 mg, and 25 °C. In addition, the effect of pH on the adsorption rates of eggshells and eggshells with membrane were detected at pH values of 5 and 5.9 and found to be 95.2, 90.5, and 73.3%. The reaction surface experiment showed that the best adsorption rate reached 99.3% after calcination at 900 °C for 2 h and a 20 min reaction. The results showed that eggshells, eggshell membranes, eggshells with membrane, and calcined eggshells could be applied to remove copper ions from industrial wastewater. The adsorption capacity of the calcined eggshell is better than that of the non-calcined eggshell and has good neutrality in acidic industrial wastewater. Therefore, it is convenient and practical for practical production and application. Likewise, this study conveys promising findings in the context of improving wastewater treatment based on a circular economy approach to waste reuse in the food industry and represents a valuable direction for future research.