Adsorption kinetics and thermodynamics of organophosphorus profenofos pesticide onto Fe/Ni bimetallic nanoparticles

Bimetallic Fe/Ni nanoparticles were synthesized and used for the removal of profenofos organophosphorus pesticide from aqueous solution. These novel bimetallic nanoparticles (Fe/Ni) were characterized by scanning electron microscopy, energy-dispersive X-ray analysis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The effect of the parameters of initial pesticide concentration, pH of the solution, adsorbent dosage, temperature, and contact time on adsorption was investigated. The adsorbent exhibited high efficiency for profenofos adsorption, and equilibrium was achieved in 8 min. The Langmuir, Freundlich, and Temkin isotherm models were used to determine equilibrium. The Langmuir model showed the best fit with the experimental data (R ² = 0.9988). Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were tested to determine absorption kinetics. The pseudo-second-order model provided the best correlation with the results (R ² = 0.99936). The changes in the thermodynamic parameters of Gibb’s free energy, enthalpy, and entropy of the adsorption process were also evaluated. Thermodynamic parameters indicate that profenofos adsorption using Fe/Ni nanoparticles is a spontaneous and endothermic process. The value of the activation energy (E _a = 109.57 kJ/mol) confirms the nature of the chemisorption of profenofos onto Fe/Ni adsorbent.     

Adsorption of heavy metals in glacial till soil

The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI), trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero charge (pH _PZC ) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II).     

伟晶岩结晶动力学和热力学及稀有金属超常富集成矿机制

本文综述了伟晶岩结晶动力学、热力学和伟晶岩熔体稀有金属元素实现超常富集成矿的机制。结晶动力学涉及成核动力学和晶体生长动力学两个方面。低成核速率和高晶体生长速率是伟晶岩结晶动力学的重要特征,在结晶过程受到水、助溶剂以及过冷条件三个因素共同制约。伟晶岩熔体的相态（超临界态）可能在伟晶岩形成和稀有金属元素超常富集中扮演重要角色。花岗伟晶岩稀有金属超常富集程度受到岩浆源区成分、岩浆结晶分异过程与熔体化学成分等因素的控制。花岗质岩浆高度分异结晶或者变质沉积岩部分熔融直接形成的成矿伟晶岩熔体均需要源岩中稀有金属元素预富集。深熔作用产生的低程度、小体积的伟晶岩熔体具有更高的稀有金属元素成矿潜力。在岩浆分异演化过程中,稀有金属元素的超常富集主要通过超临界熔体/流体、岩浆熔体作用、过冷作用实现。超临界熔体/流体发生熔体- 流体不混溶作用使稀有金属元素在熔体相和流体相间再分配和富集;岩浆熔离作用使稀有金属元素选择性分配到富挥发分的熔体中,导致稀有金属元素再次富集;过冷作用降低稀有金属矿物结晶的饱和浓度,促进稀有金属矿物结晶。熔体的化学成分（如挥发分）直接影响熔体的物理、化学性质。例如,挥发分的富集能够降低熔体黏度,促进岩浆分异结晶过程。挥发分和稀有金属元素的亲和性也控制稀有金属元素在不同相熔体中的分配和富集,显著增加稀有金属元素的溶解度和迁移富集能力,有助于伟晶岩中稀有金属超常富集和成矿。     

Adsorption characteristics of heavy metals in soil zones developed on spilite

Various soil zones such as Bw, C1, and C3 are developed on spilite. Montmorillonite, vermiculite and chlorite is moderately occurred in the C1 and C3 soil zones, in contrast montmorillonite and vermiculite are absent in Bw soils whereas illite and sesquioxide are relatively increased. The high cation exchange capacity (CEC) of montmorillonite and vermiculte and moderate CEC of chlorite and illite resulted in the high adsorption of heavy metals. The adsorption of the heavy metals on spilite soil zones was studied at different concentrations and pH levels. Heavy metals like lead, cadmium, and copper were selected for adsorption studies considering their contribution as toxic metals in the environment. The initial solute concentrations ranged from 7.0 × 10⁻³ to 1.0 × 10² mg/L. The sorption behavior of Cd²⁺, Pb²⁺, and Cu²⁺ on soil zones of spilite was investigated using the batch equilibrium technique at 25°C. The characteristics of the adsorption process were investigated using Scatchard plot analysis (q/C vs. q) by the batch equilibrium technique at 25°C. In the adsorption of heavy metals, deviation from linearity in the plot of q/C versus q was observed, indicating the presence of multi-model interaction and non-Langmuirean behavior. When the Scatchard plot showed a deviation from linearity, greater emphasis was placed on the analysis of the adsorption data in terms of the Freundlich model, in order to construct the adsorption isotherms of the metal(s) at particular concentration(s) in solutions. The adsorption behavior of these metal ions on spilite soil zones is expressed by the Freundlich isotherms. Adsorption constants and correlation coefficients for the Cd, Pb, and Cu on spilite soil zones were calculated from Freundlich plots.     

Batch and continuous removal of heavy metals from industrial effluents using microbial consortia

Bio-removal of heavy metals, using microbial biomass, increasingly attracting scientific attention due to their significant role in purification of different types of wastewaters making it reusable. Heavy metals were reported to have a significant hazardous effect on human health, and while the conventional methods of removal were found to be insufficient; microbial biosorption was found to be the most suitable alternative. In this work, an immobilized microbial consortium was generated using Statistical Design of Experiment (DOE) as a robust method to screen the efficiency of the microbial isolates in heavy metal removal process. This is the first report of applying Statistical DOE to screen the efficacy of microbial isolates to remove heavy metals instead of screening normal variables. A mixture of bacterial biomass and fungal spores was used both in batch and continuous modes to remove Chromium and Iron ions from industrial effluents. Bakery yeast was applied as a positive control, and all the obtained biosorbent isolates showed more significant efficiency in heavy metal removal. In batch mode, the immobilized biomass was enclosed in a hanged tea bag-like cellulose membrane to facilitate the separation of the biosorbent from the treated solutions, which is one of the main challenges in applying microbial biosorption at large scale. The continuous flow removal was performed using fixed bed mini-bioreactor, and the process was optimized in terms of pH (6) and flow rates (1 ml/min) using Response Surface Methodology. The most potential biosorbent microbes were identified and characterized. The generated microbial consortia and process succeeded in the total removal of Chromium ions and more than half of Iron ions both from standard solutions and industrial effluents.     

High efficiency of heavy metal removal in mine water by limestone

The removal of Cd, Cu, Ni and Zn from dilute mine water by using several geological materials including pure limestone, sand, carbonaceous limestone and brecciated limestone was performed on a laboratory scale. The results showed that to add geological materials in combination with sodium carbonate injection would notably enhance the efficiency of heavy metal removal to varying degrees. Pure limestone was found the best one among the four materials mentioned above for removing heavy metals from mine water. The removal efficiencies of pure limestone when it is ground as fine as 30–60 meshes are 58.6% for Cd, 100% for Cu, 47.8% for Ni, and 36.8% for Zn at 20°C. The optimum pH is about 8.9 to 9.1. The mechanism of higher effective removal, perhaps, is primarily due to co-precipitation under the control of calcite-related pH value. According to this research, Na₂CO₃ injection manners, including slug dosing and drip-wise, seemed to have little impact on the efficiency of heavy metal removal.     

Efficiency of compost in the removal of heavy metals from the industrial wastewater

Authorities have been applying very strict regulations for the treatment of industrial wastewater recently because of the threatening level of the environmental pollution faced. Industrial wastewater containing heavy metals is a threat to the public health because of the accumulation of the heavy metals in the aquatic life which is transferred to human bodies through the food chain. Therefore, recently, researchers have been oriented toward the practical use of adsorbents for the treatment of wastewater polluted by heavy metals. The aim of this research was to determine the retention capacity of compost for copper, zinc, nickel and chromium. For this purpose, experiments in batch-mixing reactors with initial metal concentrations ranging from 100 to 1,000 mg/l were carried. It was also observed that compost could repeatedly be used in metal sorption processes. The experiments conducted indicated that compost has high retention capacities for copper, zinc and nickel, but not for chromium. Thus, compost has been approved as a potential sorbent for copper, zinc and nickel and may find place in industrial applications. Thus, solid waste which is another source of significant environmental pollution will be reduced by being converted into a beneficial product compost.     

Adsorption kinetics of chromium(III) removal from aqueous solutions using natural red earth

Laboratory-scale-simulated experiments were carried out using Cr(III) solutions to identify the Cr(III) retention behavior of natural red earth (NRE), a natural soil available in the northwestern coastal belt of Sri Lanka. The effects of solution pH, initial Cr(III) concentration and the contact time were examined. The NRE showed almost 100 % Cr(III) adsorption within the first 90 min. [initial [Cr(III)] = 0.0092–0.192 mM; initial pH 4.0–9.0]. At pH 2 (298 K), when particle size ranged from 125 to 180 μm the Cr(III) adsorption data were modeled according to Langmuir convention assuming site homogeneity. The pH-dependent Cr(III) adsorption data were quantified by diffused layer model assuming following reaction stoichiometries: $$ \begin{aligned} 2\, {>}{\text{AlOH}}_{{({\text{s}})}} + {\text{ Cr }}\left( {\text{OH}} \right)_{{ 2\,({\text{aq}})}}^{ + } \, \to \, \left( { {>}{\text{AlO}}} \right)_{ 2} {\text{Cr}}_{{({\text{s}})}}^{ + } + {\text{ 2H}}_{ 2} {\text{O}} \quad {\text{log K 15}}. 5 6\\ 2\, {>}{\text{FeOH}}_{{({\text{s}})}} + {\text{ Cr}}\left( {\text{OH}} \right)_{{ 2\,({\text{aq}})}}^{ + } \, \to \, \left( { {>}{\text{FeO}}} \right)_{ 2} {\text{Cr}}_{{({\text{s}})}}^{ + } + {\text{ 2H}}_{ 2} {\text{O}}\quad {\text{log K 5}}.0 8.\\ \end{aligned} $$ The present data showed that NRE can effectively be used to mitigate Cr(III) from aqueous solutions and this method is found to be simple, effective, economical and environmentally benign.     

Insight into adsorption equilibrium,kinetics and thermodynamics of lead onto alluvial soil

In the present study, adsorption of lead (II) ions from aqueous solution by alluvial soil of Bhagirathi River was investigated under batch mode. The influence of solution pH, sorbent dose, initial lead (II) concentration, contact time, stirring rate and temperature on the removal process were investigated. The lead adsorption was favored with maximum adsorption at pH 6.0. Sorption equilibrium time was observed in 60 min. The equilibrium adsorption data were analyzed by the Freundlich, Langmuir, Dubinin–Radushkevich and Temkin adsorption isotherm models. The kinetics of lead (II) ion was discussed by pseudo first-order, pseudo second-order, intra-particle diffusion, and surface mass transfer models. It was shown that the adsorption of lead ions could be described by the pseudo second-order kinetic model. The activation energy of the adsorption process (E _a) was found to be ?38.33 kJ mol^?1 using the Arrhenius equation, indicating exothermic nature of lead adsorption onto alluvial soil. Thermodynamic parameters, such as Gibbs free energy (?G ⁰), the enthalpy (?H ⁰), and the entropy change of sorption (?S ⁰) have also been evaluated and it has been found that the adsorption process was spontaneous, feasible, and exothermic in nature. The results indicated that alluvial soil of Bhagirathi River can be used as an effective and low cost adsorbent to remove lead ions from aqueous solutions.     

Lead removal from wastewater using fluted pumpkin seed shell activated carbon: Adsorption modeling and kinetics

Activated carbon produced from fluted pumpkin (Telfairia occidentalis) seed shell was utilized for the removal of lead (II) ion from simulated wastewater. Adsorption tests were carried out in series of batch adsorption experiments. Several kinetic models (Bhattacharya-Venkobacher, Elovich, pseudo first and second order, intra-particle and film diffusion) were tasted for conformity to the experimental data obtained. The Langmuir and Freundlich adsorption models were also used to test the data. The amount of lead (II) ion adsorbed at equilibrium from a 200 mg/L solute concentration was 14.286 mg/g. The experimental data conform very well to the pseudo-second order equation where equilibrium adsorption capacities increased with increasing initial lead (II) concentration. The rate of the adsorption process was controlled by the film (boundary layer) diffusion as the film diffusion co-efficient values obtained from data analysis were of the order of 10 ⁶cm²/s. From the plots, the linear regression coefficient (R²) of the Langmuir model was higher than that of the Freundlich: the adsorption isotherm obeyed the Langmuir model better than the Freundlich model.     

Ultrafast removal of heavy metals by tin oxide nanowires as new adsorbents in solid-phase extraction technique

In the present research, the removal of lead(II) and copper(II) from aqueous solutions is studied, using SnO₂ nanowires as new adsorbent on solid-phase extraction disk and compared with pine core and buttonwood as biosorbents. Batch adsorption experiments were performed as a function of pH, adsorption time, solute concentration and adsorbent dose for biosorbents. Also, the pH, transfer rate of solution and metal concentration were selected as experimental parameters for the removal of heavy metals by SnO₂ nanowires. All of the parameters were optimized by experimental design method for sorbents. The experimental equilibrium adsorption data are tested for the Langmuir and Freundlich equations. Results indicate the following order to fit the isotherms: Langmuir > Freundlich, in case of lead and copper ions. The removal of Cu(II) and Pb(II) was performed by selected sorbents in the presence of interferences ions. This led to no remarkable decrease in the removal efficiency of SnO₂ nanowires. Using the SnO₂ nanowires in the wastewater treatment indicated 96.8 and 85.28% removal efficiency in only 7 min for Pb(II) and Cu(II), respectively. SnO₂ nanowires were found as reusable sorbent. Therefore, SnO₂ nanowires have a good potential for application in environmental protection.     

Adsorptive removal of eight heavy metals from aqueous solution by unmodified and modified agricultural waste: tangerine peel

Analysis was carried out using tangerine peel aiming its use as a potential adsorbent of eight heavy metal ions (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) from aqueous solution. This agricultural waste was tested both in its untreated and also chemically modified form. Based on Fourier transformation infrared spectra, a comparison of biosorbent structure before and after chemical treatment was made. Batch adsorption tests were conducted at different pH and mass of sorbent to examine the influence on the effectiveness of simultaneous removal of tested ions. Kinetic studies were conducted at optimum pH 5.0 and sorbent dosage 300 mg. The pseudo-second-order kinetic model best fit the experimental data with high correlation coefficients (r² > 0.9997). By optimizing listed parameters, high removal efficiencies (> 89%) were achieved. According to the results obtained in this study, the remediation of water polluted with heavy metals could be done using modified tangerine peel as an agricultural waste material.     

Evaluation of the removal of heavy metals in a natural wetland impacted by mining activities in Mexico

This research is focused on evaluating heavy metals (Cd, Cu, Fe, Mn, Pb, and Zn) uptake and removal by Eleocharis ovata, Cyperus manimae, Typha dominguensis, and Pteridium aquilinum in a natural wetland impacted by mining activities. We analyzed heavy metals content and distribution in native plants, soils, and water of a semipermanent natural wetland in Taxco de Alarcón, Guerrero, and we also determined the physicochemical characteristics of the water. Translocation factor (TF) and bioconcentration factor (BCF) were evaluated. Results showed that physical and chemical conditions are favorable for plants development. Correlation analysis showed a good and positive relation (0.95) between Cu and Pb in soils and plants. In the analyzed matrices: Zn (0.62–2.20 mg/L) exceeded the permissible limits in water, high concentrations of Pb and Zn (26.57–525.67 and 266.67–983.33 mg/kg, respectively) were detected in the studied soils, and Pb exceeded the normal range for E. ovata and P. aquilinum in the analyzed plants. Uptake of heavy metals in the tissues of different species was found in the following order: root > leaf. Data of TF and BCF showed that E. ovata is a tolerant plant with respect to heavy metals exposure since TF value was greater than 1. This study showed that E. ovata could be considered as a bioaccumulator of heavy metals in contaminated soils.     

Spatial distribution,mineralogy, and weathering of heavy metals in soils along zinc-concentrate ground transportation routes: implication for assessing heavy metal sources

We investigated the source of heavy metals in soils at a site in South Korea, where a ground transportation of zinc-concentrates (ZnS, sphalerite) occurs daily. Seventy soil samples were collected at the site and analyzed for residual concentrations of heavy metals, as well as their chemical and mineralogical properties. Enrichment factor was calculated based on local geochemical background level of metals in soils and confirmed the contamination of soils in the area by an anthropogenic source. The concentration data were also subjected to a Pearson correlation analysis to determine the possible influences of anthropogenic sources and identify the primary source. A slight negative correlation between heavy metals and Al, and a weak correlation between heavy metals and Fe implied that the heavy metals originated from anthropogenic inputs rather than a geogenic source. A strong positive linear correlation between Zn and other heavy metals (i.e., As, Cd, Cu, Pb, r ≥ 0.96, p ≤ 0.001) suggested the influence of a single anthropogenic source of zinc-concentrates containing all of these heavy metals. Zinc-concentrate oxidation and leaching experiments, which mimicked physical and chemical weathering in the environment, indicated that zinc-concentrate could be transformed to zinc oxides and release Cd and Pb upon precipitation. The findings in this study provide an insight into the fate of the Zn that the original form of zinc-concentrate would not remain in the soil after long-term weathering, which should be considered when source of heavy metals is identified.