Adsorption Of Nickel Research Articles

Adsorption of Nickel(II) Ions by Natural Zeolites Type

The adsorption of nickel (II) ions by natural zeolites of the Sokirnitskoe (Transcar-pathia, Ukraine) and Kholinskoye (Eastern Transbaikalia, Russia) deposits has been studied. According to X-ray phase analysis data, the zeolite-containing sample of the Sokirnitskoe deposit contains at least 75 wt. % clinoptilolite and impurity rock - quartz SiO2. The sample of the Kholinskoye deposit consists of heulandite (not less than 75 wt. %), as well as an impurity rock - potassium spar KAlSi3O8. The assessment of the ad-sorption capacity of zeolites with respect to nickel (II) ions was carried out on the basis of the analysis of adsorption isotherms. The pH of the medium of the studied aqueous solutions was 5.5–5.8. The value of ad-sorption of nickel (II) ions by heulandite is twice that for clinoptilolite and amounts to 0.104 mmol/L. The adsorption of nickel (II) ions was investigated using the Langmuir, Freundlich and Dubinin-Radushkevich models. On the basis of the Dubinin-Radushkevich adsorption model, the values of the free energy of adsorption are determined. That indicates the physical nature of the interaction of the adsorptive and the adsorbent, in the case of the zeolite of the Sokirnitskoe deposit. It is shown that the adsorption of nickel (II) ions by the zeolite of the Kholinskoye deposit proceeds according to the ion-exchange mechanism. This explains the higher adsorption values of nickel (II) ions by this sample.

PEI-Schiff base-modified mesoporous silica materials SBA-12, 15 and 16 for toxic metal ions capture (Co(II), Ni(II) and Cu(II)): Effect of morphology, post-synthetic modification and kinetic study

A series of SBA materials (SBA-12, SBA-15, and SBA-16) with polyethyleneimine (PEI) and its Schiff base variants with salicylaldehyde-modified samples (PS) have been successfully prepared and characterized. The synthesized materials were investigated by infrared spectroscopy (FT-IR), and quantification of the organic part coated on the surface was studied using thermogravimetric analysis (TGA). Nitrogen adsorption/desorption analysis at − 196 °C (N2), bright field scanning transmission electron microscopy (BF-STEM) and small angle X-ray scattering (SAXS) measurements were used to study textural properties, structure and morphology. Confirmation of heavy metal ions capture in pores of prepared materials was proved by X-ray fluorescence analysis (XRF), and nitrate anions were confirmed by FT-IR spectroscopy. Kinetic studies were performed by conductometric analysis (CA) and showed that the mathematical models could be applied to adsorption processes with a non-linear decreasing trend. This trend appeared in PS-modified SBA systems and some non-modified samples. The best overall adsorption properties were observed for material SBA-12 and its modified types. In this case, material SBA-12-PS can trap 54.38 mg g−1 of Cu(NO3)2 or 18.42 mg of Cu(II) ions, 112.84 mg g−1 of Ni(NO3)2 corresponding to 36.24 mg of Ni(II) cations, and 39.56 mg g−1 of Co(NO3)2 representing 12.74 mg of Co(II) ions. Non-modified materials show morphological effects where 2D ordered pores with hexagonal symmetry and the biggest mesopores (5.5 nm) have the best overall results in adsorption capacity of metal ions (Cu(II): 11.95 mg g−1) calculated from pseudo-second order. SBA-12 with a cubic framework and 3D ordered pores (3.8 nm) has a lower adsorption capacity than SBA-15 (Cu(II): 7.85 mg g−1), and SBA-16 with the smallest spherical pores (under 2 nm) showed the lowest overall adsorption capacity (Cu(II): 4.65 mg g−1). Kinetic rates of non-modified samples have opposite trend SBA-12 (Cu(II): 0.009 mg g−1 min−1) > SBA-15 (Cu(II): 0.002 mg g−1 min−1) > SBA-16 (Cu(II): 0.001 mg g−1 min−1). In the case of SBA-16, small pore entrances have a negative effect on the kinetic rate. For modified samples, SBA-12 with the largest surface area (896 m2 g−1) provides more space for binding of polyethyleneimine molecules (and also salicylaldehyde), which affects the best results in ion capture (Cu(II): 16.64 mg g−1). Bigger mesopores give more adsorption capacity, but capillarity makes the kinetic rate slow. SBA-16, with tiny entrance mesopores, has the lowest kinetic rate and adsorption capacity. This phenomenon was also observed in cobalt(II) adsorption, and similar results were obtained in nickel(II) adsorption. Kinetic studies point to two types of mechanisms given by the pseudo-second-order model in the case of non-modified materials, and Elovich kinetic model describes chemisorption at modified samples. These mechanisms are influenced by the significant effect of intraparticle diffusion, described by the Weber-Morris model.

Adsorption of nickel(II) ions from aqueous solutions using Malatya clay: Equilibrium, kinetic, and thermodynamic studies

AbstractThis paper evaluates Malatya clay (MC) for the removal of Ni(II) ions from aqueous solutions. For adsorption efficiency, the impacts of several factors, such as pH, starting metal ion concentration, and contact duration, were examined. The optimal initial Ni(II) ion concentration was determined to be 5 mg/L, the adsorption contact duration was 360 min, and the solution's pH was 6.27. Using scanning electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy, the surface characteristics of Malatya clay were examined. The isotherm data fit the Langmuir isotherm model, indicating chemical adsorption and likely irreversibility of the process, according to the results. At 298, 308, and 318 K, the adsorption capacities of Ni(II) were determined to be 10.267, 11.834, and 12.285 mg/g, respectively. Adsorption kinetic data revealed that the adsorption of Ni(II) metal ions followed the pseudo‐second‐order kinetic model. According to thermodynamic studies, Ni(II) ion adsorption on the MC is spontaneous and endothermic. MC has proven to be an effective and alternative material for the removal of Ni(II) ions from aqueous media due to its excellent removal ability, availability, and low cost, as well as its features such as being able to be used without any chemical treatment and being environmentally friendly.

Effects of biochar-based materials on nickel adsorption and bioavailability in soil

The potential for toxic elements to contaminate soil has been extensively studied. Therefore, the development of cost-effective methods and materials to prevent toxic element residues in the soil from entering the food chain is of great significance. Industrial and agricultural wastes such as wood vinegar (WV), sodium humate (NaHA) and biochar (BC) were used as raw materials in this study. HA was obtained by acidizing NaHA with WV and then loaded onto BC, which successfully prepared a highly efficient modification agent for nickel-contaminated soil, namely biochar-humic acid material (BC-HA). The characteristics and parameters of BC-HA were obtained by FTIR, SEM, EDS, BET and XPS. The chemisorption of Ni(II) ions by BC-HA conforms to the quasi-second-order kinetic model. Ni(II) ions are distributed on the heterogeneous surface of BC-HA by multimolecular layer adsorption, which accords with the Freundlich isotherm model. WV promotes better binding of HA and BC by introducing more active sites, thus increasing the adsorption capacity of Ni(II) ions on BC-HA. Ni(II) ions in soil are anchored to BC-HA by physical and chemical adsorption, electrostatic interaction, ion exchange and synergy.

Efficient adsorption of nickel and chromium(VI) from aqueous solutions using lignocellulose nanofibers: Kinetics, isotherms, and thermodynamic studies

Abstract The entry of heavy metals due to industrial activities into the environment is one of the major problems in this century. Nickel and chromium(VI) are the toxin elements that are used in various industries. In this study, lignocellulose nanofiber was purchased from the Nano-Novin Polymer Company (Gorgan, Iran) and used as an adsorbent for the removal of nickel and chromium(VI) ions from aqueous solutions in a batch system. The effects of pH, initial concentration, adsorbent dose, contact time, and temperature were investigated. The adsorption mechanism was determined by Langmuir, Freundlich, kinetic, and thermodynamic models. Investigation of equilibrium isotherms nickel and chromium(VI) showed that the isotherm fitted well with the Freundlich model. The pseudo-second-order model with the larger correlation coefficient had a greater fitness against experimental data in the kinetic studies. Thermodynamic parameters of both nickel and chromium such as Gibbs free energy, enthalpy, and entropy were calculated which indicated spontaneous, endothermic, and random processes, respectively. Lignocellulose nanofiber can be suggested as a good adsorbent that is highly capable of adsorbing nickel and chromium(VI) from aqueous solutions.

Competitive adsorption and immobilization of Cd, Ni, and Cu by biochar in unsaturated soils under single-, binary-, and ternary-metal systems

This study investigated the competitive adsorption and immobilization of cadmium (Cd), nickel (Ni), and copper (Cu) by biochar in unsaturated soils under single-, binary-, and ternary-metal systems. The results showed that the immobilization effects by the soil itself were in the order of Cu > Ni > Cd, and the adsorption capacities of freshly contaminated heavy metals by biochar were in the order of Cd > Ni > Cu in unsaturated soils. The adsorption and immobilization of Cd by biochars in soils was weakened by competition more in the ternary-metal system than that in the binary-metal system; the competition with Cu caused a more significant weakening effect than that with Ni. For Cd and Ni, nonmineral mechanisms preferentially adsorbed and immobilized Cd and Ni compared to mineral mechanisms, but the contributions of the mineral mechanisms to the adsorption gradually increased and became dominant with increasing concentrations (at average percentages of 62.59%−83.30% and 41.38%−74.29%, respectively). However, for Cu, the contributions of the nonmineral mechanisms to Cu adsorption were always dominant (average percentages of 60.92%−74.87%) and gradually increased with increasing concentrations. This study highlighted that the types of heavy metals and coexistence should be focused when remediating heavy metal contamination in soils.

Modified Shrimp-Based Chitosan as an Emerging Adsorbent Removing Heavy Metals (Chromium, Nickel, Arsenic, and Cobalt) from Polluted Water

Water quality is under constant threat worldwide due to the discharge of heavy metals into the water from industrial waste. In this report, we introduce a potential candidate, chitosan, extracted and isolated from shrimp shells, that can adsorb heavy metals from polluted water. The waste shrimp shell chitosan was characterized via Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The adsorption capacity of heavy metals on the modified shrimp shell was measured using an inductively coupled plasma mass spectrometry before and after adsorption. The highest adsorption of arsenic, nickel, and cobalt was 98.50, 74.50, and 47.82%, respectively, at neutral pH, whereas the highest adsorption of chromium was 97.40% at pH 3. Correspondingly, the maximum adsorption capacities of MSS for As, Cr, Ni, and Co were observed to be 15.92, 20.37, 7.00, and 6.27 mg/g, respectively. The application of Langmuir and Freundlich isotherm models revealed that the adsorption processes for the heavy metals were statistically significant (r2 > 0.98). The kinetic studies of metal adsorption, using modified shrimp shell, were well explained by the pseudo-second-order kinetic model with linear coefficients (r2) of >0.97. The presence of a greater number of functional groups on the adsorbent, such as N–H coupled with H–O, –COO−, C–H, N–N, and C–O–C, was confirmed by FTIR analyses. Furthermore, SEM-EDX analysis detected the presence of elements on the surface of modified shrimp shell chitosan. This noteworthy adsorption capacity suggests that MSS could serve as a promising, eco-friendly, and low-cost adsorbent for removing toxic heavy metals including Cr, Ni, As, and Co and can be used in many broad-scale applications to clean wastewater.

Using fish scales as a new biosorbent for adsorption of nickel and copper ions from wastewater and investigating the effects of electric and magnetic fields on the adsorption process

In this study, fish scales (Pomadasys kaakan's scales) were used as new biosorbent for removing Ni2+ and Cu2+ ions from wastewater. The effects of electric and magnetic fields on the absorption efficiency were also investigated. The effects of sorbent content, ion concentration, contact time, pH, electric field (EF), and magnetic field (MF) on absorption efficiency were assertained. In addition, the isotherm of absorption was studied in this work. This study revealed that electric field and magnetic field have significant effects on the absorption efficiency of ions from wastewater. An increase in the electric field enhanced the removal percentage of the ions and accelerated the absorption process by up to 40% in comparison with the same condition without an electric field or a magnetic field. By increasing contact time from 10 to 120 min, the removal of Ni2+ ions was increased from 1% to 40% and for Cu2+ ions, the removal increased from 20% to almost 95%, respectively. In addition, increasing pH, ion concentration and scales dose increased removal percentage effectively. The results indicated that using fish scales for Cu2+ ions absorption is ideal due to the very high removal percentage (approximately 95%) without using either an electric or magnetic field.

Study on the Adsorption Properties and Mechanisms of CO on Nickel Surfaces Based on Density Functional Theory

In this work, the adsorption of CO onto the surface of the transition metal Ni at different coverage levels was explored based on the density functional theory (DFT). The corresponding periodic slab plate models were established, and the adsorption parameters and CO electronic states on different nickel surfaces under different coverage (0.11 mL, 0.25 mL and 0.5 mL) were calculated. The results showed that the most stable adsorption sites on Ni (111) and Ni (100) crystal surfaces were valley sites, while the most stable adsorption sites on a Ni (110) surface was a short bridge site. By comparing the energy of the same adsorption sites, it was found that the adsorption of CO on a Ni (100) crystal surface was superior to the other two surfaces. Furtherly, from the perspective of the electronic structure, the density of states (DOSs) of Ni atoms and CO molecules were calculated before and after adsorption. The density of states showed that the main factor of surface adsorption generation originates from hybridization among the orbitals. This article provides insight into the mechanisms of the nickel adsorption of CO.

Nickel(II) adsorption in aqueous solutions with cost-effective mesoporous Bitlis pumice stone

Nickel(II) adsorption in aqueous solutions with cost-effective mesoporous Bitlis pumice stone

Investigation of the adsorption of nickel(II) ions by natural sorbents

Investigation of the adsorption of nickel(II) ions by natural sorbents

Recovery Process for Critical Metals: Selective Adsorption of Nickel(II) from Cobalt(II) at Acidic Condition and Elevated Temperature

Effective and sustainable separation processes for critical metals, especially for the physicochemically similar elements nickel and cobalt in battery recycling, are of great interest in the future. Selective adsorption represents a highly potential process for this purpose. In this publication, a silica adsorbent functionalized with an amino-polycarboxylate derivate (HSU331) was investigated regarding the selective adsorption of Ni(II) in the presence of Co(II) in acidic solution (pH range at equilibrium 1.8–2.3) at elevated temperature. Comparable maximum equilibrium loadings ([Formula: see text]) for Ni(II) and Co(II) of 0.59 μmol(Ni(II)) · μmol(Ligand)-1 (18.3 mg(Ni(II)) · g(Adsorbent)-1), and 0.52 μmol(Co(II)) · μmol(Ligand)-1 (16.0 mg(Co(II)) · g(Adsorbent)-1), respectively, were achieved at T = 50°C in single-component experiments. Under competitive conditions, the Ni(II) loading remained constant at 0.60 μmol(Ni(II)) · μmol(Ligand)-1 (18.4 mg(Ni(II)) · g(Adsorbent)-1), while the Co(II) loading drastically decreased to 0.09 μmol(Co(II)) · μmol(Ligand)-1 (2.7 mg(Co(II)) · g(Adsorbent)-1) in an equimolar dual-component system. Calculated stability constants of 3 · 103 and 0.7 · 103 L · mol-1, respectively, for the formed metal ion complexes of Ni(II) and Co(II) onto the adsorbent HSU331, clarify the clear selectivity of the adsorbent towards Ni(II) in the presence of Co(II) even at elevated temperature ( T = 50°C).

Predictive model based on artificial neural network for estimating the adsorption of nickel and lead on a natural and synthetic support

Predictive model based on artificial neural network for estimating the adsorption of nickel and lead on a natural and synthetic support

Study on the equilibrium and kinetics of nickel adsorption on rice husk: the role of activation

Rice husk is an agricultural byproduct that is produced in huge quantities during the rice milling process. Following the trend of utilizing agricultural waste, rice husk is activated by many activators to synthesize heavy metal ion adsorbent materials. This work presents the results of the study on the adsorption of nickel ions (Ni2+) by activated rice husks. The husk was activated by three agents (NaOH, acetic acid, and H2O2), which removed 73.29 percent of the hemicellulose and 60.25 percent of the ligin (calculated by the Chesson-Datta method). The influence of time on the adsorption capacity of Ni2+ ions of activated rice husks was carried out with an initial concentration of Ni2+ ions of 160mg/L and a pH of 5.5. The concentration of adsorbent was 1,0 g.L-1. After 80 minutes of adsorption, the equilibrium adsorption capacity reached 33.33 mg.g-1. The maximum adsorption capacity calculated by the Langmuir adsorption model was 57.46 mg.g-1. Three kinetic models (Lagergren's apparent first-order kinetics, second-order apparent kinetics and Webber-Morris internal diffusion kinetics) were also studied and analyzed.

Sodium Alginate/β-Cyclodextrin Reinforced Carbon Nanotubes Hydrogel as Alternative Adsorbent for Nickel(II) Metal Ion Removal.

Water pollution issues, particularly those caused by heavy metal ions, have been significantly growing. This paper combined biopolymers such as sodium alginate (SA) and β-cyclodextrin (β-CD) to improve adsorption performance with the help of calcium ion as the cross-linked agent. Moreover, the addition of carbon nanotubes (CNTs) into the hybrid hydrogel matrix was examined. The adsorption of nickel(II) was thoroughly compared between pristine sodium alginate/β-cyclodextrin (SA-β-CD) and sodium alginate/β-cyclodextrin immobilized carbon nanotubes (SA-β-CD/CNTs) hydrogel. Both hydrogels were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectral analysis, field emission scanning electron microscopy (FESEM), electron dispersive spectroscopy (EDX), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area analysis. The results showed SA-β-CD/CNTs hydrogel exhibits excellent thermal stability, high specific surface area and large porosity compared with SA-β-CD hydrogel. Batch experiments were performed to study the effect of several adsorptive variables such as initial concentration, pH, contact time and temperature. The adsorption performance of the prepared SA-β-CD/CNTs hydrogel was comprehensively reported with maximum percentage removal of up to 79.86% for SA-β-CD/CNTs and 69.54% for SA-β-CD. The optimum adsorption conditions were reported when the concentration of Ni(II) solution was maintained at 100 ppm, pH 5, 303 K, and contacted for 120 min with a 1000 mg dosage. The Freundlich isotherm and pseudo-second order kinetic model are the best fits to describe the adsorption behavior. A thermodynamic study was also performed. The probable interaction mechanisms that enable the successful binding of Ni(II) on hydrogels, including electrostatic attraction, ion exchange, surface complexation, coordination binding and host-guest interaction between the cationic sites of Ni(II) on both SA-β-CD and SA-β-CD/CNTs hydrogel during the adsorption process, were discussed. The regeneration study also revealed the high efficiency of SA-β-CD/CNTs hydrogel on four successive cycles compared with SA-β-CD hydrogel. Therefore, this work signifies SA-β-CD/CNTs hydrogel has great potential to remove Ni(II) from an aqueous environment compared with SA-β-CD hydrogel.

Layered metal sulfide NMTS for rapid removal of radioactive strontium ions from aqueous solution

A one-step hydrothermal method was used to synthesize a quaternary metal sulfide material, NMTS, to remove strontium ions from simulated radioactive wastewater, in which metal tin was replaced by tin and magnesium salts to reduce the cost of the raw materials. The adsorption characteristics and behavior of Sr2+ were studied using batch experiments. NMTS has a layered structure, and the approximate molar ratio of Na:Mg:Sn:S is 4:1:10:23, with an approximate 61% reduction in the raw material cost compared to NaTS. NMTS exhibited ultrafast kinetics for Sr2+ with rapid adsorption of 97.1% in 0.5 min and 99.8% at an equilibrium time of 3 min, followed by the pseudo-second-order model and Langmuir model with a maximum adsorption amount of 52.6 mg/g at 298 K. NMTS had a high affinity for Sr2+ with Kd values of >106 at pH values ranging from 4 to 11. The adsorption of Sr2+ mainly involves ion exchange and surface adsorption. Ion exchange Na+ for Sr2+ was predominant with initial Sr2+ concentrations ranging from 5 to 20 mg/L, and both ion exchange and surface SrS bonding interactions occurred with initial Sr2+ concentrations higher than 20 mg/L. Sodium and potassium ions had little effect on the adsorption of Sr2+, whereas the presence of calcium and magnesium ions greatly affected it. In addition, NMTS also exhibited high selectivity for the adsorption of cobalt, nickel, and manganese, followed by Ni2+ > Sr2+ > Mn2+ > Co2+. NMTS is a promising adsorbent for removing Sr ions from aqueous solutions.

Adsorption of Heavy Metal Ions Copper, Cadmium and Nickel by Microcystis aeruginosa.

To investigate the treatment effect of algae biosorbent on heavy metal wastewater, in this paper, the adsorption effect of M. aeruginosa powder on heavy metal ions copper, cadmium and nickel was investigated using the uniform experimental method, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and TG-DSC comprehensive thermal analysis. The experimental results showed that the initial concentration of copper ion solution was 25 mg/L, the temperature was 30 °C, the pH value was 8 and the adsorption time was 5 h, which was the best condition for the removal of copper ions by algae powder adsorption, and the removal rate was 83.24%. The initial concentration of cadmium ion solution was 5 mg/L, the temperature was 35 °C, the pH value was 8 and the adsorption time was 4 h, which was the best condition for the adsorption of cadmium ion by algae powder, and the removal rate was 92.00%. The initial nickel ion solution concentration of 15 mg/L, temperature of 35 °C, pH value of 7 and adsorption time of 1 h were the best conditions for the adsorption of nickel ions by algae powder, and the removal rate was 88.67%. The spatial structure of algae powder changed obviously before and after adsorbing heavy metals. The functional groups such as amino and phosphate groups on the cell wall of M. aeruginosa enhanced the adsorption effect of heavy metal ions copper, cadmium and nickel. Additionally, M. aeruginosa adsorption of heavy metal ions copper, cadmium, nickel is an exothermic process. The above experiments show that M. aeruginosa can be used as a biological adsorbent to remove heavy metals, which lays a theoretical foundation for the subsequent treatment of heavy metal pollution by algae.

Study on the Adsorption Mechanism of Cobalt and Nickel in Manganese Sulfate by δ-MnO2.

Manganese has excellent performance in removing metal ions from aqueous solutions, but there are few studies on the adsorption and removal of heavy metal impurities in metal salt solutions. In this paper, the adsorption of cobalt and nickel ions in MnSO4 solution by δ-MnO2 prepared from two different manganese sources was studied. The optimum adsorption conditions were as follows: When the concentration of Mn2+ was 20 g/L, δ-MnO2 addition was 10 g/L, Co2+ concentration was 80 mg/L, Ni2+ concentration was 80 mg/L, reaction time was 60 min, reaction temperature was 80 °C, and pH value was 7, the adsorption rate of Co2+ and Ni2+ reached more than 80%. The manganese dioxide adsorbed by heavy metals was analyzed and detected. The results showed that MnOOH appeared in the phases of both kinds of δ-MnO2, and their morphologies were dense rod-like structures with different lengths and flake-like structures of fine particles. Co and Ni were distributed on the surface and gap of MnO2 particles, and the atomic percentage of Co was slightly higher than that of Ni. The new vibration peaks appeared near wave numbers of 2668.32, 1401.00, and 2052.19 cm–1, which were caused by the complexation of cations such as Co2 + and Ni2 + with hydroxyl groups. Some cobalt and nickel appeared on the surface of δ-MnO2, and the surface oxygen increased after adsorption. The above characterization revealed that the adsorption of cobalt and nickel in manganese sulfate by δ-MnO2 was realized by the reaction of its surface hydroxyl with metal ions (M) to form ≡SOMOH.

Adsorption Study of Continuous Heavy Metal Ions (Pb2+, Cd2+, Ni2+) Removal Using Cocoa (Theobroma cacao L.) Pod Husks.

The serious toxicological effects of heavy metal ions in aquatic ecosystems have motivated the search for alternatives to reduce contamination of water sources from industrial wastewater. In this work, continuous adsorption of nickel, cadmium, and lead was assessed using a packed bed column filled with Cocoa (Theobroma cacao L.) pod husks widely available in the northern region of Colombia. The physicochemical characterization of the agricultural biomass was performed to quantify its chemical composition by bromatological, FT-IR, and energy-dispersive X-ray spectroscopy (EDS). The breakthrough curves were constructed for all heavy metal ions with bed depth of 4 and 7.5 cm, taking aliquots at 10, 30, 60, 90, 120, 150, 180, 210, 240, and 270 min. Moreover, experimental data were fitted to adsorption models in continuous mode to predict adsorptive performance (Adams–Bohart, Thomas, and Yoon–Nelson). For the FT-IR analysis of biomass before and after adsorption, the most representative bands occur around 3200–3900 cm−1 attributed to the presence of hydroxyl groups, showing the destruction of the peaks of lignocellulosic materials. The breakthrough curves revealed that for a 7.5 cm bed, adsorption performance reported the following order of promising results: Pb2+ > Ni2+ > Cd2+; while for a 4 cm bed, Pb2+ > Ni2+. The mechanism of adsorption of the evaluated metals onto cocoa pod husk was attributed to cationic exchange and microprecipitation due to the presence of Ca, K, and Si in the structure of the bio-adsorbent. Finally, the continuous adsorption was modeled under the mathematical expressions of Adams–Bohart, Thomas, and Yoon–Nelson reporting good fitting with correlation coefficient above 0.95.

Construction of a sandwich-like Gr/Ni composite coating on AZ91D magnesium alloy to achieve excellent corrosion and wear resistances in the seawater

Preventing AZ91D magnesium alloy from severely wear and corrosion should be of significance so as to extend its applications. In this work, we systemically investigated graphene (Gr) doping concentration to influence the structure and performance of Gr/Ni composite coatings on AZ91D Mg alloy in the seawater. The results showed that the optimal Gr doping Gr/Ni composite coating on Mg alloy could possess much higher hardness and better adhesive strength as well as much lower wear rate in the seawater. Moreover, the novel composite sandwich structure was utilized to construct multi-interfacial Gr/Ni composite coating on AZ91D Mg alloy, which successfully achieved much more excellent long-term corrosion and wear resistances in the marine. Density functional theory calculations clarified the mechanism of sequential adsorption of nickel to graphene, indicating that it easily gave rise to graphene agglomeration in electroplating process. However, the multi-interfaces could provide more stretching space for graphene sheets and reduce the folding tendency of graphene. These results indicated that the sandwich-like structure Gr/Ni composite coating brought excellent properties for AZ91D magnesium alloy to enhance its services in the marine and aviation environments.