Maximum Adsorption Research Articles

Development of an effective method for purifying trypsin using a recombinant inhibitor

A trypsin affinity material was prepared by covalently immobilizing buckwheat trypsin inhibitor (BTI) on epichlorohydrin-activated cross-linked agarose gel (Selfinose CL 6 B). The optimal conditions for activating Selfinose CL 6 B were 15 % epichlorohydrin and 0.8 M NaOH at 40 °C for 2 h. The optimal pH for immobilizing BTI was 9.5. BTI-Sefinose CL 6 B showed a maximum adsorption capacity of 2.25 mg trypsin/(g support). The material also displayed good reusability, retaining over 90 % of its initial adsorption capacity after 30 cycles. High-purity trypsin was obtained from locust homogenate using BTI-Selfinose CL 6 B through one-step affinity chromatography. The molecular mass and Km value of locust trypsin were determined as 27 kDa and 0.241 mM using N-benzoyl-DL-arginine-nitroanilide as substrate. The optimal temperature and pH of trypsin activity were 55 °C and 9.0, respectively. The enzyme exhibited good stability in the temperature range of 30–50 °C and pH range of 4.0–10.0. BTI-Selfinose CL 6 B demonstrates potential application in the preparation of high-purity trypsin and the discovery of more novel trypsin from various species.

Fabrication of nanozeolite-Y/chitosan composite based on rice husks for efficient adsorption of methylene blue dye: kinetic and thermodynamic studies

In this work, three solid adsorbents were synthesized, namely, nanozeolite-Y prepared from rice husks ash by a sol-gel method as a green biosource (ZN), chitosan as a cationic biopolymer (CS), and nanozeolite-Y/chitosan composite (CSZ). An eco-friendly composite that consists of chitosan and nanozeolite-Y was used to combine the advantages of nanoparticles with biopolymers two materials to increase the removal % of methylene blue dye. All the synthetized solid adsorbents were investigated using TGA, nitrogen adsorption, SEM, TEM, FTIR, XRD, and zeta potential. The results showed that CSZ particles had a high specific surface area (432.3 m2/g), mesoporosity (with an average pore diameter of 2.59 nm), a smaller TEM particle size (between 28.6 and 60.7 nm), a lot of chemical functional groups, and high thermal stability. CSZ exhibited the maximum adsorption capacity (141.04 mg/g) towards methylene blue. The adsorption nature of methylene blue onto CS and CSZ is endothermic, spontaneous, and a physical adsorption process, while it is exothermic, nonspontaneous, physical adsorption process in the case of ZN, as confirmed by thermodynamic results. Pseudo-second order, Elovich, Dubinin-Radushkevich, Freundlich, Langmuir, Temkin, and adsorption models all fit the MB adsorption well, with correlation coefficients reaching about 0.9997. Nitric acid was found to be the best desorbing agent, with a desorption efficiency of about 99%.

Adsorption of haem by magnetic chitosan microspheres: Optimal conditions, adsorption mechanisms and density functional theory analyses

Magnetic chitosan microspheres (Al@CTS@Fe3O4) were prepared for haem separation via chemical cross-linking of chitosan, Fe3O4 and AlCl3·6H2O. The properties of the Al@CTS@Fe3O4 microspheres were investigated through techniques including XRD, TEM, FTIR, BET analysis, SEM, TG, VSM, XPS and pHpzc analysis. The haem adsorption of Al@CTS@Fe3O4 was optimized via a Box–Behnken design (BBD) with three operating factors: Fe3O4 dose (0.5–1.3 g), AlCl3·6H2O concentration (0.25–1.25 mol/L) and glutaraldehyde dose (2–6 mL). The optimal haem adsorption effect was achieved with 1.1 g of Fe3O4, 0.75 mol/L AlCl3·6H2O, and 3 mL of glutaraldehyde. The adsorption kinetics and isotherms demonstrated that haem adsorption by the Al@CTS@Fe3O4 microspheres was best described by the pseudo-second-order model. The maximum adsorption capacity is 33.875 mg/g at pH 6. After six adsorption–desorption cycles, the removal of haem still reached 53.83 %. The surface adsorption mechanism of haem on Al@CTS@Fe3O4 can be attributed to electrostatic, hydrogen bonding, and n-π interactions. Thermodynamic calculations indicated that the adsorption process is spontaneous, with the microspheres preferentially accepting electrons and haem preferentially providing electrons. Consequently, the Al@CTS@Fe3O4 microspheres exhibit considerable potential as adsorbents for haem separation.

Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chlorophenol using bio-based activated carbon: Thermodynamics, kinetics and cytotoxicity evaluation

This study investigates the use of peanut husk biowaste (PH) activated carbon to remove 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chlorophenol (4-CP) from water. Acid activation of PH enhances its structure, creating pores in the activated carbon. SEM, TEM, and XRD confirm the effectiveness of this process. BET analysis shows the increase in surface area from 0.775 to 547 ​m2 ​g−1 for the PH and PH-AC samples. PH-AC tested against 2,4-D and 4-CP, optimizing pH, contact time, pollutant dose, PH-AC dose, and temperature for maximum adsorption efficiencies. Maximum adsorption capacity for 2,4-D and 4-CP is 165.9 and 99.4 ​mg ​g−1, respectively, higher than previous research. Kinetics, adsorption, and thermodynamic studies reveal the endothermic and spontaneous nature of the adsorption process. The adsorbent demonstrates stability and long-term applicability, with substantial adsorption capacities for four cycles. Cytotoxicity studies confirm non-toxicity and environmental friendliness of PH-AC material. These findings highlight the potential of PH-AC for wastewater treatment.

Enhanced uranium extraction using a nanostructured photothermal hydrogel membrane

Uranium is the basic resource in nuclear energy and a sword of two sides. The accidental release of radioactive uranium to the environment may cause serious impact on the environment and living creatures. Herein, a nanostructured hydrogel-based solar evaporator with in-situ formed nanostructures is designed for simultaneous solar evaporation and uranium extraction from polluted water. To be specific, poly(acrylic acid) and gelatin with embedded carbon black nanoparticles coated on a cotton cloth self-assemble into nanostructures via salting-out and acid treatment to reduce the light reflectivity and enhance the specific surface area for uranium adsorption. Numerical simulation confirms that the evaporation-induced flow accelerates the diffusion of uranyl ions towards the adsorbent. Under solar irradiation of 1 kW m−2 a maximum uranium adsorption capacity of 443.2 ± 18.1 mg g−1 is achieved in 20 ppm uranium-spiked water, meanwhile a high solar evaporation rate of 3.75 kg m−2 h−1 is reached, hence, the solar evaporator is ranked among the most powerful adsorbents/evaporators. This work provides a cost-effective and scalable approach for dealing with uranium-polluted water.

Utilization of Base and Acid Modified Rice Husk-Corncobs Composite for Removal of Chromium (VI) Ion in Simulated Tannery Wastewater

In the ever-increasing blind race of industrialization and urbanization environmental contamination by toxic heavy metal ions is becoming a serious issue for both scientists and masses. Hence, the objective of this paper was to evaluate the utilization of base (BMOD) and acid (AMOD) modified rice husk-corncobs composite for the removal of chromium (VI) Ion in simulated tannery wastewater using appropriate standard techniques. SEM-EDX, XRD and FTIR characterizations revealed the elemental composition, crystallographic structures and the chemical bonds respectively. The results of the sorption kinetic study showed that the data fitted well with the pseudo-second order model for both acid modified (AMOD) and base modified (BMOD) biosorbent with a maximum adsorption of 28.46 mg/g and 39.66 mg/g respectively. The results of the sorption isotherm study showed that they both fitted Freundlich isotherm model. From the results obtained, rice husk and corn cob were effective biosorbent for the removal of Cr (VI) ion from tannery effluent.

Activation and Zr precursor influence on UiO-66-NH2 composites for efficient cationic and anionic dye removal

This study investigates the synthesis of UiO-66-NH2@HTC composites, focusing on the control of surface charge, textural properties, and crystallinity. Surface charge modification was achieved through activation processes to enhance affinity for specific pollutants. By utilizing ZrCl4 and ZrOCl2⋅8H2O precursors, the textural properties were optimized, leading to higher mesopore content and improved crystallinity with the ZrOCl2⋅8H2O precursor. The UiO-66-NH2(ZrCl4)@HTC composite exhibited a crystallinity of 51.7 %, with 40 % mesopores and 57 % micropores, while the UiO-66-NH2(ZrOCl2)@HTC composite showed a crystallinity of 60 %, consisting of 60 % mesopores and 37 % micropores. Adsorption followed the Langmuir isotherm model, with maximum adsorption capacities of 263.1 mg/g for methylene blue (MB) and 277.77 mg/g for Congo red (CR), driven by hydrogen bonding and electrostatic interactions. The activated UiO-66-NH2@HTC composites demonstrated remarkable reusability. These findings emphasize the significant role of surface charge modification, pore structure optimization, and crystallinity enhancement in developing high-performance adsorbents.

Anchoring nanoscale zero-valent iron within bacterial cellulose particles for boosting efficient adsorption of Co(II) and Sr(II) from seawater: Dual system and varying adsorption mechanisms

Increasing attention has been paid to radioactive wastewater to direct discharge in Japan or accidental leaks. Strontium-90 (90Sr) and Cobalt-60 (60Co) are the most hazardous nuclides in waste discharged form nuclear reactors. Because of their high solubility and long half-lives, these radioisotopes can persist for hundreds of years before decaying to negligible levels. Herein, a green and biodegradable material nanoscale zero-valent iron (nZVI) supported by bacterial cellulose particles (BCP-nZVI) is constructed for the first time to adsorb Co2+ and Sr2+ in single and binary systems. BCP-nZVI shows superior adsorption capacities of Co2+ and Sr2+in a single system within a wide range of pH values from 5 to7, while the coexistence of Co2+ adsorption inhibits the Sr2+ in binary system. Pseudo-second-order dynamics model and Langmuir isothermal model can be indicated the BCP-nZVI adsorption progress with 107.10 mg/g (Co2+) and 64.96 mg/g (Sr2+) maximum adsorption capacity. BCP-nZVI has outstanding stability, allowing it to be stored for more than one month with compromising its performance. More importantly, BCP-nZVI exhibits exceptional removal efficiency of Co2+(92.53%) and Sr2+(58.62%) removal in natural seawater systems. The mechanism investigation illustrates the high adsorption capacity of BCP-nZVI for Co2+ is controlled by redox and hydroxyl complexation. While Sr2+ is controlled by hydroxyl complexed adsorption, thus it has weak against interference by cations like Na+, Ca2+, etc. BCP-nZVI exhibits the advantages of high adsorption capacity, wide pH range, strong stability, and good applicability in natural seawater, which has excellent potential for application in radioactive ions removal.

Efficient removal of Pb(II) and Cd(II) from water by polyethyleneimine-amidated sepiolite-sodium alginate composite microspheres: Characterization and mechanistic analysis

In order to improve the physicochemical properties of heavy metal adsorbents, researchers developed a novel composite microsphere material (SEI) by incorporating Sepiolite (Sep) and cross-linked polyethyleneimine (PEI) with sodium alginate (SA) as a carrier. The stability of the SEI under normal use conditions was high by thermogravimetric analysis, and COOH, OH, and NH2 functional groups were detected by FTIR, which were confirmed to be involved in adsorption. It was found that the adsorption rate of SEI on Pb(II) and Cd(II) obeyed a pseudo-second-order kinetic model, while the adsorption pattern was closely related to the Langmuir equation. Notably, the maximum adsorption capacity of SEI for Pb(II) and Cd(II) was 1099.93 mg/g and 112.89 mg/g, respectively, at 30 °C. In addition, thermodynamic analyses showed that the adsorption process was spontaneous, with entropy increase along with heat absorption. After six adsorption and desorption cycles, the removal of Pb(II) and Cd(II) by SEI remained above 90 %. These findings suggest that SEI is a promising and environmentally friendly material for the removal of Pb(II) and Cd(II).

Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam Shell-Derived Calcium Sources.

The increasing contamination of water sources by heavy metals necessitates the development of efficient and sustainable adsorption materials. This study evaluates the potential of nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for Cu ions in aqueous solutions. Both powders were synthesized using microwave irradiation at 700 W for 5 min, resulting in nano-sized rod-like particles confirmed as HA by X-ray diffraction (XRD). Bio-HA exhibited higher crystallinity (67.5%) compared to Chem-HA (34.9%), which contributed to Bio-HA's superior adsorption performance. The maximum adsorption capacities were 436.8 mg/g for Bio-HA and 426.7 mg/g for Chem-HA, as determined by the Langmuir isotherm model. Kinetic studies showed that the Cu ion adsorption followed the pseudo-second-order model, with Bio-HA achieving equilibrium faster and displaying a higher rate constant (6.39 × 10⁻4 g/mg·min) than Chem-HA (5.16 × 10⁻4 g/mg·min). Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, with Bio-HA requiring less energy (ΔH° = 39.00 kJ/mol) compared to Chem-HA (ΔH° = 43.77 kJ/mol). Additionally, the activation energy for Bio-HA was lower (41.62 kJ/mol) than that for Chem-HA (46.39 kJ/mol), suggesting better energy efficiency. The formation of a new Cu2(OH)PO4 phase after adsorption, as evidenced by XRD, confirmed that the Cu ions replaced the Ca ions in the HA lattice. These findings demonstrate that Bio-HA, derived from natural sources, offers environmental benefits as a recyclable material, enhancing heavy metal removal efficiency while contributing to sustainability by utilizing waste materials and reducing an environmental impact.

Solvothermal synthesis of Zr-based MOFs with mixed linker as adsorbent for methyl orange in water

Abstract UiO-66 is one type of Zr-based MOF consisting of ZrO4(OH)4 polyhedral. Synthesis of materials UiO-66 mixed linker with additional acetic acid modulator was successfully carried out by the solvothermal method at 120°C. UiO-66 modified with mixed linker can improve stability in water that has systematically and functionally modulated pores. When the concentration of each linker increases, the linkers merge in one place and produce cluster defects. UiO-66 mixed linker was synthesized with a ratio of adding H2BDC and NH2BDC of 3:1 to moles of ligand. The X-ray diffraction (XRD) pattern and Fourier transform infrared (FTIR) spectra of the synthesized material have the same pattern with the peak characteristics of UiO-66 and UiO-66-NH2. The synthesized material has a spherical morphology with a rough surface. The performance of the materials as an adsorbent for methyl orange (MO) dyes in water reached a maximum adsorption capacity of 202.82 mg/g for materials UiO-66 mixed linker (75% H2BDC and 25% NH2BDC). The adsorption results for all the synthesized materials followed the apparent pseudo-second-order kinetics and Langmuir isotherm. The adsorption mechanism between the adsorbent and methyl orange dyes consists of π-π interactions, hydrogen bonds, and electrostatic interactions.

Adsorption of natural dye phycocyanin by means of Laponite®: Synthesis and characterization of the hybrid obtained

This work addresses the use of Laponite® clay in various applications, focusing on its adsorption capacity and improvement of properties in water-based products. It describes the synthesis of Laponite® hybrids with the pigmented cyanobacterium phycocyanin (PC) to evaluate the adsorption capacity of the dye. This research addresses the importance of Laponite® clay in improving rheological properties of water-based products due to its ability to interact with components in aqueous solutions. Laponite® can be effectively dispersed in water, enhancing the dispersion of other elements in solution and preventing aggregation of solids. The structure and properties of synthetic Laponite® are described, highlighting its use in the textile industry as an additive for pigments and the formation of gels. Experimentally, Laponite® is used to adsorb phycocyanin, a cyanobacterial pigment, with the aim of achieving maximum adsorption. A design of experiments with different experimental conditions, including pH, addition of silane and surfactant, is used. A detailed analysis of the characterization of the resulting hybrids is presented, including colour, total solar reflectance (TSR), thermal analysis (TGA), EDS, FTIR and X-ray diffraction (XRD) measurements. The results show successful adsorption of the pigment in all experiments, with adsorption percentages above 97%. The colour of the hybrids is evaluated and the total solar reflectance is analyzed, highlighting their importance in applications such as coatings and printed textiles. Infrared spectroscopy and X-ray diffraction are used to study the structural properties of the hybrids. For future work, it is intended to be able to apply the hybrids obtained on an industrial scale in the colouring of textiles and plastic polymers.

Removal of malachite green in wastewater and its mechanism by three-dimensional graphene oxide-based aerogels

Malachite green (MG) is a significant water pollutant due to its widespread use and harmful properties, making its effective removal crucial. Graphene oxide (GO) has emerged as a promising material for dye adsorption. Doping GO into cellulose aerogels enhances mechanical properties and prevents GO dissolution. Many reports claim the advantages of GO in adsorption, but challenges remain in understanding and optimizing the adsorption of MG in three-dimensional cellulosic GO (CLGO) aerogels. In this study, three-dimensional CLGO aerogels were prepared using the freeze-drying method. They achieved an MG maximum adsorption capacity of 33.98 mg g−1, and the adsorbent still had 97.04 % adsorption capacity at the seventh adsorption–desorption cycle. The photothermal properties of the CLGO aerogels were also studied, contributing to the development of the zero-liquid discharge (ZLD) post-processing concept. Molecular force field simulations indicated that π-π interaction is the primary force between MG and CLGO aerogels in the absorption process. We believe our research will guide the future optimization of MG specialized absorbent.

Adsorption and kinetic studies of dyes onto BaFe12O19 Ferrite Nanoparticles

Abstract In this work, Barium hexaferrite (BaFe12O19) nanoparticles were used for industrial waste water treatment from methylene blue (MB) and congored (CR) dyes. Batch adsorber with mechanical stirring column was used to test various experimental parameters like contact time, initial dye concentration and adsorbent dosage for the removal of these dyes. For the removal of MB and CR dyes using magnetic nanoparticles, the maximum adsorption capacities were 200 and 124.5 mg/g respectively. The maximum removal efficiencies were 90 % for MB removal onto the nanoparticles and 80% for CR removal. In order to analyze the kinetic data, pseudo first and second order kinetic models have been used. For all studied variables and based on correlation coefficient (R) values and graphical presentation, the results confirm that pseudo second order model fits well the experimental data.

Uncovering fantastic synergistic lithium adsorption with manganese-titanium based composite nanospheres: Mild synthesis and molecular dynamics simulation insights

In light of the burgeoning energy technology sector and the ever-growing demand for lithium across diverse industrial domains, conventional lithium extraction methods have been proven inadequate due to their limited production capacity and high operational costs. This work introduces a novel approach to the manganese-titanium based composite HMTO (Mn:Ti=1:4) lithium ion-sieve (LIS) nanospheres, employing lithium acetate dihydrate, manganese carbonate and titanium dioxide P25 as the primary materials. These nanospheres exhibit relatively uniform spherical morphology, narrow size distribution, small average particle size (ca. 55 nm), large specific surface area (43.58 m2 g−1) and high surface O2− content (59.01%). When utilized as the adsorbents for Li+ ions, the HMTO (Mn:Ti=1:4) LIS demonstrates a fast adsorption rate, approaching equilibrium within 6.0 h with an equilibrium adsorption capacity (qe) of 79.5 mg g−1 and a maximum adsorption capacity (qm) of 87.26 mg g−1 (initial concentration C0: 1.8 g L−1). In addition, the HMTO (Mn:Ti=1:4) also delivers a high lithium extraction from the simulated high magnesium-lithium molar ratio salt lake brine (Mg:Li=103), achieving a qe of 33.85 mg g−1 along with a remarkable selectivity (αMgLi=2192.76). Particularly, the HMTO (Mn:Ti=1:4) LIS showcases a satisfactory recycling adsorption performance. The adsorption capacity remains at a high level, even that determined after the 5th cycle (55.45 mg g−1) surpasses that of the most recently reported adsorbents. Ultimately, the fantastic synergistic lithium adsorption mechanism is deliberately uncovered by leveraging the ion exchange principles and molecular dynamics (MD) simulations.

Adsorptive membrane separation for eco-friendly decontamination of chlorpyrifos via biochar-impregnated cellulose acetate mixed matrix membrane.

In this work, the phase inversion approach is used to synthesize a blended mixed matrix membrane from cellulose acetate polymer and sugarcane bagasse biochar. The experiments were carried out to estimate the extent of chlorpyrifos (CPS) pesticide removal. The results showed that the removal rate was more than 99% in making the filtered water suitable enough for domestic use. The physical and functional characteristics of the membranes, such as permeability, and contact angle were identified. The changes in the membrane characteristics were observed using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction both before and after the experimental trials. Experiments were conducted to assess not only the rejection characteristics of CPS, as a function feed concentration, but also the effect co-ions on the rejection used to analyze the composition both before and after filtration. The effects of initial CPS concentration, biochar loading, and co-ions on the membrane were investigated. The membranes showed contact angles between 70° and 97° and a permeability between 0.25 × 1010 m Pa-1 s-1 and 0.31 × 1010 m Pa-1 s-1. The effective removal of CPS from the contaminated aqueous stream was attributed to a combination of adsorptive uptake and membrane-based separation. CPS was found to get adsorbed onto the membrane matrix through an intraparticle diffusion mechanism along with an irreversible monolayer adsorption. The membrane-solute adsorptive interaction was represented by Langmuir isotherm and intraparticle diffusion models with a maximum adsorption capacity of 192.3 mg g-1. The findings indicated the efficacy of biochar-cellulose acetate mixed matrix membrane for sustainable and eco-friendly treatment of chlorpyrifoscontaminated water.

Adsorption of toxic metals from greywater using coconut husk biochar and spent green tea

The discharge of wastewater into ground and surface waters can cause human and ecological health problems, hence eco-friendly, sustainable and cost-effective methods for removing toxic metals from wastewater are required. The study employed coconut husk biochar and spent impra ginseng flavoured green tea to adsorb cadmium (Cd), chromium (Cr) and lead (Pb) from greywater. The adsorption capacity of coconut husk biochar ranged from 88.70 % to 98.20 % for cadmium, 78 %–96 % for chromium and 95.71 %–99.29 % for lead whilst the spent impra ginseng flavoured green tea ranged from 94.03 % to 96.87 % for cadmium, 52 %–74 % for chromium and 98.52 %–99.48 % for lead. The maximum adsorption capacity (Qe) of coconut husk biochar ranged from 235.64 to 1132.40 mg/g for Cd, 1.31–8.80 mg/g for Cr and 58.85–415.80 mg/g for Pb. Lead demonstrated the highest affinity for the binding of coconut husk biochar and spent impra ginseng flavoured green tea adsorbent with a trend of Pb > Cd > Cr. Coconut husk biochar and spent impra ginseng flavoured green tea adsorbent were suitable for the toxic metals adsorption in the greywater. Cr showed different removal efficiencies where coconut husk biochar showed more effective removal than spent impra ginseng flavoured green tea. The application of coconut husk biochar and spent impra ginseng flavoured green tea in wastewater treatment is a green technology means and can lead to zero pollution of freshwater.

Valorization of coffee agro-industrial residue for biochar production: Use as adsorbent for methylene blue removal

This research explores using thermally modified residual coffee grounds as a bioadsorbent for removing methylene blue (MB) from aqueous solutions. The study investigates the impact of pH on adsorption capacity, emphasizing its significant influence. Kinetic studies reveal that the pseudo-first-order (PFO) model accurately describes the MB removal process, with correlation coefficients (R²) close to 1 for all samples. The Freundlich model provided the best fit for residual coffee grounds, while the Langmuir model was most suitable for biochar 1. The BiDR model provides the best fit with high R² values, indicating efficient removal for biochar 2 and biochar 3. Notably, the research shows that MB adsorption is effective without requiring pH adjustments, thereby reducing environmental impacts. The maximum adsorption capacities were 40.85, 20.35, 19.52 and 41.98 mg.g−1 using residual coffee grounds, biochar 1, biochar 2 and biochar 3, respectively. Overall, this study demonstrates the practicality of using thermally activated coffee grounds as an efficient adsorbent for removing textile dyes from effluents and highlights the potential of alternative uses for coffee grounds and biochar residues in environmental applications.

Preparation of diatomite-based porous ceramics and their adsorption properties for Cu2+

Diatomite-based porous ceramics were prepared by wet grinding and high temperature calcination with diatomite as the main raw material. The structure and properties of the ceramics were characterized by SEM, XRD, and FI-TR detection techniques. The results show that the diatomite-based porous ceramics are mainly quartz crystal phase and contain a large amount of Si-OH. Their pore size distribution is 500∼3500 nm, the specific surface area is 6.14 m2/g, and the porosity is 47.8%. The static adsorption process of Cu2+ in water by ceramic particles conforms to the quasi-second-order kinetic model, and the adsorption equilibrium is reached after 6 h with the maximum adsorption capacity of 4.5 mg/g. The Thomas model can be applied to represent the dynamic adsorption of Cu2+ in water. In the adsorption of Cu2+, pH exerts a strong influence. In solution, Cu2+ forms a ligand with hydroxyl surface functional groups on the surface of ceramics and pores through electrostatic interaction, and the hydrogen on the hydroxyl group exchanges with Cu2+, so that Cu2+ can be removed.

Utilization of macadamia nutshell-derived activated carbon for enhanced congo red adsorption

This study addresses the challenge of removing Congo red (CR) from aqueous solutions using activated carbon (AC) derived from macadamia nutshells (MNS). A unique two-step carbonization and pyrolysis process was employed to produce MNS-AC with high surface area and porosity. Key experimental variables, including initial CR concentration, contact time, and pH, were systematically varied in batch mode. Results indicated that the modified AC achieved significantly higher removal percentages compared to unmodified charcoal. At pH 2.0 and an initial dye concentration of 50 mg L−1, CR removal reached 97.48 % for MNS-AC3. The maximum adsorption capacity (qmax) of 58.29 mg g−1 was observed at an initial dye concentration of 200 mg L−1. The pseudo-second-order kinetic model closely matched the experimental data, and equilibrium data analysis using Langmuir and Dubinin-Radushkevich (D-R) isotherm models provided excellent fits. This research demonstrates the potential of using industrial biomass waste to develop sustainable solutions for dye removal in wastewater treatment.