Biosorption of Cu2+, Co2+ and Ni2+ from aqueous solution by modified corn silk: Equilibrium, kinetics, and thermodynamic studies

Acid-activated corn silk as a promising phytosorbent for uptake of Malachite green and Cd (II) ion from simulated wastewater: equilibrium, kinetic and thermodynamic studies

Malachite green (MG) dye and cadmium metal ion are toxic pollutants that should be removed from aqueous environment. The recent study aimed to examine the adsorption behavior of MG dye and Cd (II) from wastewater onto low-cost adsorbent prepared by activating corn silk with nitric acid (ACS) and characterized by SEM, FTIR, XRD, BET and TGA. The optimum MG and Cd (II) adsorption was observed at pH 7 and pH 9 and maximum uptake of both pollutants was at 0.5 g dosage, 60 mins contact time and 20 mg/L initial concentration. The retention of dye and metal ion by the studied adsorbent was best fit to Langmuir isotherm and Pseudo-second order kinetics. The maximum monolayer coverage capacity of ACS for MG dye and Cd (II) ion was 18.38 mg/g and 25.53 mg/g, respectively. Thermodynamic studies predicted a spontaneous reaction with exothermic process for MG dye whereas an endothermic and spontaneous process was confirmed for Cd ion based on estimated parameters. The adsorption mechanism of MG dye and Cd (II) uptake was by combination of electrostatic interaction, pore diffusion, ion exchange, pie-pie attraction, hydrogen bonding, and complexation. The adsorbed pollutants were effectively desorbed with significant regeneration efficiency after successive five cycles that proved the potential of low-cost biosorbent for selective sequestration of cationic dye and divalent metal ion from effluents.

Retention properties and mechanism of agricultural waste maize whisker on atmospheric mercury

Mercury (Hg) is a global pollutant transmitted mainly through the atmosphere, posing a serious threat to biological survival and human health. Porous materials, with high specific surface area, high porosity, and high adsorption, are particularly suitable for the purification of atmospheric Hg mixtures. However, plant porous materials are rarely directly used for atmospheric Hg purification. In this study, the properties and mechanism of maize whisker in removing atmospheric Hg were analyzed. The results show that the Hg content in the whiskers increases significantly as the initial Hg concentration increases, and 79.38% Hg can be removed by 0.2 g maize whiskers after 1 h exposure when the initial Hg concentration is 0.1 μg m-3, indicating that maize whiskers can accumulate atmospheric Hg rapidly and effectively. The hole diameter of the maize whisker is between 0.83 and 3.06 μm, which is suitable for the adsorption of small substances. Correlation analysis shows that maize whiskers have a significant correlation between atmospheric Hg retention and its specific surface area, pore size, medium pore ratio, and micropore ratio, suggesting that the maize whisker hole feature has a significant influence on its ability to retain atmospheric Hg. Compared with the energy profiles before and after Hg treatment, the peak of Mg decreased after Hg adsorption. Fourier infrared spectrometer analysis suggests that functional groups such as -OH, -COOH, and -O- are involved in the adsorption process. The change in pH value shows an obvious effect on the overall change in zeta potential in the adsorption process. Therefore, a variety of mechanisms, including physical adsorption, electrostatic adsorption, complexation, chelation, and ion exchange, are involved in Hg retention with the maize whisker. This study reveals the important potential value of agricultural waste maize whiskers in the purification of atmospheric heavy metal Hg.

Equilibrium, kinetics and thermodynamics of biosorption of U(VI) by Jonesia quinghaiensis strain ZFSY-01 isolated from the wastewater of a uranium mine

The adsorption ability of a native Jonesia quinghaiensis strain ZFSY-01, a microorganism isolated from uranium tailing wastewater, to U(VI) in wastewater under different conditions was studied in this work. The results showed that 391.5 mg U/g and 78.3% of adsorption capacity and efficiency were achieved under an optimum adsorption condition, respectively. Especially, the adsorption capacity of this strain reached the maximum (Q=788.9 mg U/g) under 100 mg/L of strain dosage. Simultaneously, the linear regression coefficients for the used isothermal sorption model indicate that the biosorption process is compatible with the Freundlich isotherm, the Temkin isotherm and the Halsey isotherm model. Based on the fitted kinetic parameters, the data from the experiments fit well with models of pseudo-second-order kinetics and intraparticle diffusion, suggesting that the strain ZFSY-01 immobilized U(VI) by physical and chemical adsorption. In addition, thermodynamic parameters demonstrated that the sequestration of U(VI) by the strain is spontaneous and endothermic. Based on the above analysis, strain ZFSY-01 can effectively remove U(VI) ions from high- or low-concentration uranium-containing wastewater and is expected to become a promising biological adsorbent.

Nickel adsorption from waters onto Fe3O4/sugar beet pulp nanocomposite

In this study the magnetic nanocomposite material was synthesized with Fe₃O₄ impregnated to sugar beet pulp using chemical precipitation technique. Ni(II) removal performance of magnetic nanocomposite was investigated under different environmental conditions such as contact time, adsorbent dose, pH, initial heavy metal concentration, etc. The experimental studies have shown that, 81.2% Ni(II) removal efficiency was achieved at optimal conditions (25 mg/L initial Ni(II) concentration at 40 minute contact time, 200 rpm shaking speed, 5 g/L nanocomposite dose and pH 6.6). Freundlich and Langmuir isotherm experiments were performed and correlation coefficients were determined as 94.5% and 99.4%, respectively. The maximum adsorption capacity of material was achieved as 9.36 mg/g. These findings indicate that the adsorption that takes place is a monolayer process. The results of the pseudo-second order kinetic model (R² = 0.9947) indicate the chemisorptions process is used for Ni(II) removal using the electrostatic interaction. Thermodynamic studies illustrated that Ni(II) adsorption onto nanocomposite are exothermic and causes a decrease in the entropy. The adsorption of Ni(II) ions is non-spontaneous except for at low temperature and low initial concentrations. Nanocomposite characterization was illuminated with XRD, FT-IR, BET, TGA, TEM, SEM/EDX analysis.

Adsorption of Ni2+ in aqueous solution by KMnO4 modified biomass: investigation on adsorption kinetics and modification mechanism

In this study, KMnO₄ modification was proved to effectively increase the Ni²⁺ adsorption capacity of biomass. In order to clarify the KMnO₄ modification mechanism, the Ni²⁺ adsorption characteristics of KMnO₄ modified corncob (PPCB) under adsorption time, pH and Ni²⁺ concentration were studied. The results showed that the adsorption was the pseudo second-order kinetic process, indicating that chemisorption was the dominated process, which followed the Langmuir isotherm model and the highest Ni²⁺ adsorption capacity of PPCB reached 35.6 mg/g. By KMnO₄ modification, the corncob was oxidized to generate carboxylates, and the MnO₂ (reduction product) was loaded on the modified corncob, both carboxylates and MnO₂ increased the Ni²⁺ adsorption capacity of PPCB. The molecular dynamic results indicated the carboxylate structures had the strongest adsorption capacity. Moreover, the Ni²⁺ removal efficiency of KMnO₄ modified biomass decreased linearly with the increase of lignin content in biomass, while KMnO₄ modified lignin showed a good adsorption performance, indicating that the cross-linked structures between lignin and other components in the biomass could inhibit the adsorption capacity of PPCB.

Polymeric Biomass Derived Adsorbents for Co(II) Remediation, Recycling and Analysis

The gradual replacement of conventional materials with materials tailored to the green development goals is one of the needs of the day. Correspondingly, this article reviews and integrates, for the first time, the gathered knowledge on the use of the adsorbents based on polymeric biomasses (biosorbents) for a cleaner separation of cobalt (Co) from synthetic and actual solutions. It is a two-part comprehensive approach that debates the Co biosorption potential of bio-based polymers from the perspective of their virtual and real applications for decontamination, recovery, and analytical purposes. First, the removal performances of these materials to batch and fixed column biosorption of Co(II) from mono-component and multi-metallic laboratory solutions are systematized and discussed. Following that, the focus of the first part is shifted to the analytical capabilities of the biosorbents proposed for Co(II) quantification from synthetic solutions. The second section considers the polymeric biomasses successfully incorporated in practical strategies for the removal and recovery of Co(II) from real solutions. The opportunities provided by the use of biosorbents for the development of accurate and greener procedures in Co(II) analysis are also highlighted. The directions in which the research on this topic should be continued and strengthened are suggested.

Performance and retention mechanisms of corn silk to atmospheric heavy metal lead

Atmospheric heavy metals are seriously harmful, and porous materials have unique advantages in the control of air pollutants. However, the direct use of plant porous materials to purify atmospheric heavy metals are rare. So agricultural waste corn silk with porous structures was selected to analyze the retention capability and mechanism to the atmospheric lead. The results show that the corn silk can effectively retain atmospheric lead in natural growing state or fixed experimental conditions. The analysis of a total of 765 corn silk samples from 17 different regions in Shandong province, China, shows that atmospheric lead is the main source of lead in the corn silk, and corn silk can be used for biological monitoring of atmospheric lead to some extent. Based on the analysis with different techniques including scanning electron microscope (SEM), energy spectrum dispersive X-ray spectrometer (EDS), Fourier infrared spectrometer (FTIR) and Zeta potential, the effective retention of lead by corn silk is due to a variety of mechanisms, including physical adsorption, electrostatic adsorption, complexation, chelation and ion exchange. So agricultural waste corn silk has great potential in the application of biosorption or preparation of porous materials in purification of atmospheric heavy metals.

Preparation of adsorbent based on water treatment residuals and chitosan by homogeneous method with freeze-drying and its As(V) removal performance

Although the chitosan-WTRs particulate adsorbent prepared by embedding method has been proved to have arsenic adsorption capacity, the capacity of it is greatly weakened compared with the original water treatment residuals (WTRs). In this study, WTRs and chitosan were used as raw materials to prepare a new kind of adsorbent beads by a homogeneous method. At the same time, in order to enhance the adsorption capacity and reduce the limitation of kinetics, freeze-drying method was chosen to dry the adsorbent. The WTRs-chitosan beads by homogeneous method (WCB) were characterized by SEM, XRD, XPS and other methods. According to the characterization results, there are regularly arranged pores inside the particles, and the iron in the particles mainly exists in the form of amorphous iron oxyhydroxide. According to the results of batch experiment, the pseudo-second-order kinetic model has a higher degree of fit, indicating that the WCB adsorbs As(V) mainly by chemical adsorption. The maximum adsorption capacity estimated from the Langmuir isotherm model is 42.083 mg/g, which is almost same as the WTRs. Weak acid and neutral conditions are conducive to adsorption, while alkaline conditions have a significant inhibitory effect on arsenic adsorption.

Biosorption of Co2+ Ions from Aqueous Solution by K2HPO4-Pretreated Duckweed Lemna gibba

The wastewater of the many industries that use divalent cobalt (Co2+)-containing compounds has elevated levels of this metal. Thus, novel technology is needed to efficiently remove Co2+ ions from aqueous solutions. Biosorption is a low-cost technique capable of removing heavy metals from contaminated water. This study aims to evaluate the performance of KH2PO4-pretreated Lemna gibba (PLEM) as a biosorbent of Co2+ in aqueous solutions tested under different conditions of pH, particle size, and initial Co2+ concentration. Kinetic, equilibrium, and thermodynamic studies were conducted. The capacity of biosorption increased with a greater initial Co2+ concentration and was optimal at pH 7.0 and with small-sized biosorbent particles (0.3–0.8 mm). The pseudo-second-order sorption model best describes the experimental data on Co2+ biosorption kinetics. The Sips and Redlich-Peterson isotherm models best predict the biosorption capacity at equilibrium. According to the thermodynamic study, biosorption of Co2+ was endothermic and spontaneous. The effect of pH on the biosorption/desorption of Co2+ suggests that electrostatic attraction is the main biosorption mechanism. SEM-EDX verified the presence of Co2+ on the surface of the pretreated-saturated biosorbent and the absence of the metal after desorption.

Elaboration of novel polyaniline@Almond shell biocomposite for effective removal of hexavalent chromium ions and Orange G dye from aqueous solutions

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g^-1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Synthesis and application of sugarcane bagasse cellulose mixed esters. Part II: Removal of Co2+ and Ni2+ from single spiked aqueous solutions in batch and continuous mode

Sugarcane bagasse cellulose succinate trimellitate (SBST) was prepared by a one-pot synthesis method. The synthesis of this novel mixed ester was investigated by a 2³-factorial design. The parameters investigated were time, temperature, and succinic anhydride mole fraction (χ_SA). The responses evaluated were the adsorption capacity (q_Co2+ and q_Ni2+), weight gain (wg), and number of carboxylic acid groups (n_T,COOH). ¹³C Multiple Cross-Polarization solid-state NMR spectroscopy, ¹H NMR relaxometry, and Fourier-transform infrared spectroscopy were used to elucidate the SBST structure. The best SBST reaction conditions were 100 °C, 660 min, and χ_SA of 0.2, which yielded SBST with a wg of 57.1%, n_T,COOH of 4.48 mmol g^-1, and q_Co2+ and q_Ni2+ of 0.900 and 0.963 mmol g^-1, respectively. The maximum adsorption capacities (Q_max) (pH 5.75, 25 °C) estimated by the Redlich-Peterson model for Co²⁺ and Ni²⁺ were 1.16 and 1.29 mmol g^-1. The Δ_adsH° values for Co²⁺ and Ni²⁺ adsorption obtained by isothermal titration calorimetry were 8.03 and 6.94 kJ mol^-1. Regeneration and reuse of SBST were investigated and the best conditions applied for fixed-bed column adsorption in five consecutive cycles. SBST was fully desorbed and Q_max values for Co²⁺ (0.95 mmol g^-1) and Ni²⁺ (1.02 mmol g^-1) were estimated using the Bohart-Adams model.

Calcined Umbonium vestiarium snail shell as an efficient adsorbent for treatment of wastewater containing Co (II)

In the present study, the Umbonium vestiarium snail shell (UVS) was used as an abundant and low-cost resource for the removal of Co (II) from aqueous solution. The characteristics of calcined Umbonium vestiarium snail shell (CUVS) were analyzed using FTIR, SEM, MAP, EDAX, and BET analyses. The results showed that the specific surface area of the CUVS was obtained 17.02 m2/g which was an acceptable amount. The presence of Co (II) in the adsorbent structure was confirmed by EDAX, and Map analyses after Co (II) adsorption showed that the adsorbent successfully adsorbed Co (II) from aqueous solution. The effect of different parameters such as, contact time, initial concentration of cobalt ion, the adsorbent dose, and pH value was also investigated. The maximum efficiency of cobalt ion adsorption was measured 93.87% at a pH value of 6, contact time of 80 min, the adsorbent dose of 3 g/L, and initial ion concentration of 10 mg/L. Also, Langmuir, Freundlich, and D-R isotherm models were used to determine the most appropriate isotherm model for cobalt ion adsorption. The adsorption equilibrium data were better fitted with the Langmuir model with a maximum adsorption capacity of 93.46 mg/g. Additionally, the average free energy of adsorption was evaluated in the amount of 1.4085 KJ/mol, revealing a physical adsorption. Moreover, the kinetic behavior study showed that the experimental data follow the pseudo second order kinetic model to the value of correlation coefficient.

A Comparative Sorption Study of Ni (II) form Aqueous Solution Using Silica Gel, Amberlite IR-120 and Sawdust

The presence of heavy metals in water causes serious problems and their treatment before incorporating into the water body is a challenge for researchers. The present study was conducted to compare the sorption study of Ni (II) using silica gel, amberlite IR-120 and sawdust of mulberry wood in batch system under the influence of pH, initial Ni (II) concentration and contact time. It was observed that sorption process was depending upon pH and maximum sorption was achieved at pH 7.0. Kinetic data were well fitted into pseudo-second order kinetic model due to high R2 values and closeness of experimental sorption capacity and calculated sorption capacity of pseudo-second order. Isotherms study showed that Langmuir is one of the most suitable choices to explain sorption data due to high R2 values. The monolayer sorption capacities of silica gel, amberlite IR-120 and sawdust were found to be 33.33, 25.19, and 33.67 mg g−1, respectively. Desorption study revealed that NaCl is one of the most appropriate desorbent. It may be concluded from this study that sawdust is a suitable sorbent due to low cost, abundant availability and recycling of the materials for further study.

Adsorption behavior of Cu(II) and Co(II) using chemically modified marine algae

In this study, brown algae-modified biomass Padina sanctae crucis was used for copper (Cu(II)) and cobalt (Co(II)) heavy metal ions adsorption in synthetic wastewater. The effects of solution pH and adsorption efficiency for Cu(II) and Co(II) removal from aqueous solutions were studied. In order to study the kinetic behavior of adsorption, pseudo-first-order, pseudo-second-order kinetic models, liquid film penetration, and Ritchie second-order models were used. The results showed that the pseudo-second-order kinetic model was able to describe adsorbent behavior in comparison to the other models. Moreover, in order to study adsorbent equilibrium behavior, Langmuir and Freundlich isothermal models were used. Based on the Langmuir model, the adsorption capacity of Co(II) and Cu(II) was determined and their values were 13.73 and 13.996 mg/g, respectively. It was shown that both metal ions adsorption process is favorable and adsorption is physical. In this research, thermodynamic parameters were also studied in order to determine Gibbs free energy for both metal ions which were negative, indicating that metal ions adsorption process is spontaneous and the degree of self-adsorption increases as temperature increases.

Chromium removal from industrial wastewater using Phyllostachys pubescens biomass loaded Cu-S nanospheres

In this paper, a new surface modification method was reported for the preparation of Phyllostachys pubescens powder as an effective adsorbent for the removal of chromium. Complex copper sulfide (Cu-S)nanospheres were evenly dispersed and loaded into the internal surface of the adsorbent, which provided both the ion exchange and oxidative-reductive properties. The composite showed an excellent adsorption efficacy for Cr(III) and Cr(VI). The surface properties of the obtained materials were characterized by FTIR and SEM. Maximum adsorption for Cr(III) and Cr(VI) was observed at pH 6.1 and 1.9, respectively. The experimental sorption equilibrium data were modeled using Langmuir and Freundlich isotherm equations. It was found that the maximum adsorption capacities of Cr(III) and Cr(VI) were 52.30 mg g-1 and 94.25 mg g-1, respectively. The adsorption mechanism analysis inferred that the major adsorption mode of Cr(III) was ion exchange, and Cr(VI) was oxide-reduction.

Characterization of the biosorption properties of dormant spores of Aspergillus niger: a potential breakthrough agent for removing Cu2+ from contaminated water

The biosorption capacity of Aspergillus niger spores for Cu²⁺ was found to be 25.3 mg g⁻¹, which was two times higher than that of its mycelium (10.1 mg g⁻¹).