Investigation of Strontium (II) Sorption Kinetic and Thermodynamic onto Straw-derived Biochar

Biochars have attracted much research attention recently because of their potential applications in many environmental areas. In this study, rice straw-derived biochars produced at different pyrolysis temperatures (550–750°C) were used as adsorbents for the removal of strontium (II) under different experimental conditions of time, pH, and temperature. Sr(II) sorption equilibrium occurs after 30 min and its sorption maximum achieved at pH 6. The kinetic data obtained were analyzed to predict the constant rate of sorption using three common kinetic models: pseudo-first-order, pseudo-second-order equation, and intraparticle diffusion equation. The pseudo-second-order model was suitable for describing the sorption kinetics for the removal of Sr(II) from aqueous solution onto straw-derived biochar. Sorption of Sr(II) onto biochar was endothermic. Biochar has the highest Sr(II) sorption capacity in comparison to other adsorbents.     

Immobilisation of TiO2-nanoparticles on sewage sludge and their adsorption for cadmium removal from aqueous solutions

In this study, pure TiO₂-nanoparticles and TiO₂/sewage sludge (TS) as biomass material were synthesised via a sol–gel method. The adsorption potential of nanosized TiO₂ and TS for removal of Cd(II) was investigated in a batch system. The prepared adsorbents were characterised using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The XRD analysis showed that pure TiO₂ is in amorphous phase before calcination and in anatase phase at annealing temperature of 400 °C. TiO₂/sewage sludge that calcined at 400 °C (TS⁴⁰⁰) was found to be the best adsorbent for cadmium removal from aqueous solution. Kinetic and isotherm studies were carried out by considering the parameters, pH, initial concentration and contact time. The optimum pH value for Cd(II) adsorption onto TS⁴⁰⁰ was found to be 6. Langmuir isotherm showed better fit than Freundlich isotherm and the maximum adsorption capacity was found to be 29.28 mg/g which is higher than that of many other adsorbents reported in literature. The sorption kinetic data were well fitted with a pseudo-second-order model. These results demonstrated that TS⁴⁰⁰ was readily prepared and is the promising and effective solid material for the removal of Cd(II) from aqueous solutions.     

Heavy metal ions adsorption and photodegradation of remazol black XP by iron oxide/silica monoliths: Kinetic and equilibrium modelling

The adsorption of heavy metal ions (Cr³⁺, Pb²⁺ and Cd²⁺) by metal oxide monoliths (Fe₂O₃ and Fe₂O₃/SiO₂) synthesized via nanocasting method using SiO₂ monoliths as a template was studied. The adsorption experiments were performed in different batches by varying key parameters and the equilibrium between the adsorbents and metal ion solution was achieved in ～120?min at pH 6. The maximum monolayer adsorption efficiency for Pb (II), Cr (III) and Cd (II) ions was 850, 770 and 690?mg/g, respectively, for the magnetic Fe₂O₃/SiO₂ monoliths. The experimental data show best fit with the pseudo-second-order reaction type. The adsorption data found to be well fitted using Freundlich and Langmuir adsorption isotherms. The adsorption process was exothermic and spontaneous in nature, as confirmed by the thermodynamic parameters. Furthermore, the photocatalytic degradation of an industrial dye e.g., remazol black XP (RxP) by Fe₂O₃/SiO₂ monoliths was done from wastewater and the photocatalytic efficiency of the monoliths (using different amount) has been evaluated under visible light source which gives the best results (97.8%) for the monolith concentration 0.10?g/L.     

Relation between biochar physicochemical characteristics on the adsorption of fluoride,nitrite, and nitrate anions from aqueous solution

This study describes how physicochemical characteristics of rice straw-based biochar, prepared at a different pyrolysis temperature (550, 650, 750°C) and treated by HNO₃ or H₂O₂ or KMnO₄, influence on its removal capacity for fluoride, nitrite, and nitrate anions from the water. Biochars exhibit broad pore size distribution from wide mesopores (5.0?nm) to narrow micropores (1.0?nm). Furthermore, all prepared biochars have both basic sites (2.8–8.13?meq/g) and acidic ones (1.8–9.3?meq/g) on their surface. The effect of biochar porosity, acidity, and basicity on anions adsorption was studied. KMnO₄- and H₂O₂-treated biochar give high nitrite and nitrate uptake in micropore range (0.03–0.05 cc/g) and mesopore range (0.01–0.06 cc/g) while HNO₃-treated ones give low uptake in both micropore range (0.02–0.021 cc/g) and mesopore range (0.01–0.05 cc/g). As a conclusion, no particular characteristics seem to be an influential essential in the removal of anionic contaminants. These observations are useful to guide the surface modification of biochars as efficient sorbents for specific application needs and removal of environmental pollutants.     

Production and characterization of carbon-based adsorbents from waste lignocellulosic biomass: their effectiveness in heavy metal removal

Abstract

In this study, hazelnut shell and walnut shell which are the agricultural wastes existent abundantly in many countries were pyrolyzed at different temperatures in the temperature range of 400–700?°C in order to optimize the physicochemical properties of biochars. The biochars with large surface area were used to removal of lead (Pb²⁺) ions, one of the most important heavy metal pollutant, from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, BET, SEM, partial and elemental analysis techniques. In order to determine the adsorption characteristics of both biochars, batch adsorption experiments were carried out under different experimental conditions. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of Pb²⁺ ions from aqueous solution. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion model, and the model constants were investigated.     

Synthesis and application of TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles as novel adsorbent for removal of Cd(II), Hg(II) and Ni(II) ions from water samples

In the current study, SiO₂/Fe₃O₄ core–shell nanoparticles functionalized with TiO₂, using a simple method and application for removal of Cd(II), Hg(II) and Ni(II) ions from aqueous solution. The structure of the resulting product was confirmed by X-ray diffraction spectrometry, transmission electron microscopy (TEM), pH_pzc and Brunauer, Emmett and Teller methods. The average diameter of TiO₂/SiO₂/Fe₃O₄ nanoparticles according to TEM was obtained around 48 nm. In batch tests, the effects of pH, initial metal concentration, contact time and temperature were studied. Adsorption of metal ions was studied from both kinetics and equilibrium point of view. Maximum adsorption capacity of Cd(II), Hg(II) and Ni(II) on TiO₂/SiO₂/Fe₃O₄ nanoparticles was 670.9, 745.6 and 563.0 mg g^?1, respectively. Adsorption–desorption results showed that the reusability of nanoparticles was encouraging. This adsorbent was successfully applied to removal Cd(II), Hg(II) and Ni(II) ions in real samples including tap water, electronic wastewater and medical wastewater.     

Magnetic and dielectric properties of cadmium substituted nickel cobalt nanoferrites

Nano particles of Cd_XNi_(0.5?X)Co_0.5Fe₂O₄ (x = 0.0, 0.1, 0.2 and 0.3) were prepared by coprecipitation method. The lattice constant and distribution of cation in A-site and B-site have been deduced through X-ray diffraction (XRD) data analysis. The lattice constant (?) was found to increase with increase in Cd²⁺ concentration in the spinel structure of Ni–Co ferrites. The saturation magnetization was found to decrease with increase in Cd concentration for all the samples. It is observed that the Curie temperature (T_c) is higher than in bulk counterpart. The dielectric constant increases with increase in Cd concentration. This increase in dielectric constant is attributed to the formation of Fe³⁺ ion in the octahedral site which increases the hopping between Fe³⁺ and Fe²⁺.     

Preparation and characterization of zeolite from waste Linz-Donawitz (LD) process slag of steel industry for removal of Fe3+ from drinking water

Cubical-shaped zeolite A was synthesized from the Linz-Donawitz (LD) process slag of the Steel Industry, utilizing conventional fusion-assisted hydrothermal treatment. Morphological and Physico-chemical characterizations were performed by various characterization techniques. A weight ratio of 1:1.2 (LD-slag: NaOH) was maintained during fusion, which provides a better binding effect with better mechanical stability to the zeolite framework. Fe³⁺ adsorption studies were performed at 273, 298, 303, and 308 K, respectively, within the range of 10–40 mg L⁻¹ Fe³⁺ ion concentration for kinetic and isotherm studies. A maximum adsorption capacity of 27.55 mg g⁻¹ was obtained at a 1.4 g L⁻¹ adsorbent dosage, with 99.99% Fe³⁺ ion removal. Moreover, the Fe³⁺ adsorption study obeyed the pseudo-second-order kinetic model, whereas multistage diffusion controlled the adsorption process. Langmuir isotherm model best fitted the equilibrium data suggesting the highly negative charge over the adsorbent surface played a vital role in the electrostatic attraction of Fe³⁺ ions. Isomorphic replacement of silicon by aluminum ion imparted a highly negative charge over the zeolite surface in the primary structure unit. For real-life sample drinking water, the Fe³⁺ ion removal efficiency increases to 97.7%.     

Combined photo-Fenton-SBR process for antibiotic wastewater treatment

The study examined combined photo-Fenton-SBR treatment of an antibiotic wastewater containing amoxicillin and cloxacillin. Optimum H₂O₂/COD and H₂O₂/Fe²⁺ molar ratio of the photo-Fenton pretreatment were observed to be 2.5 and 20, respectively. Complete degradation of the antibiotics occurred in one min. The sequencing batch reactor (SBR) was operated at different hydraulic retention times (HRTs) with the wastewater treated under different photo-Fenton operating conditions (H₂O₂/COD and H₂O₂/Fe²⁺ molar ratio). The SBR performance was found to be very sensitive to BOD₅/COD ratio of the photo-Fenton treated wastewater. Statistical analysis of the results indicated that it was possible to reduce the Fe²⁺ dose and increase the irradiation time of the photo-Fenton pretreatment. The best operating conditions of the combined photo-Fenton-SBR treatment were observed to be H₂O₂/COD molar ratio 2, H₂O₂/Fe²⁺ molar ratio 150, irradiation time 90 min and HRT of 12 h. Under the best operating conditions, 89% removal of sCOD with complete nitrification was achieved and the SBR effluent met the discharge standards.     

杂原子掺杂生物质碳催化丙烷直接脱氢制丙烯

碳材料以其低成本、良好的化学稳定性和热稳定性等优异特性被广泛应用于各种催化反应中。本研究利用来源广泛的天然脱脂棉为原材料, 通过原位气相掺杂的方法制备了N掺杂、B掺杂、BN共掺杂的生物质碳材料, 并将其应用在丙烷直接脱氢制丙烯反应中。研究发现, 与未掺杂的生物质碳相比, 杂原子掺杂的生物质碳均表现出更高的丙烷转化率和丙烯选择性, 而且N、B单独掺杂的生物质碳材料催化性能优于BN共掺杂的生物质碳材料, 其中N掺杂的生物质碳具有最优催化性能: 在600 ℃反应温度下, 丙烷转化率达到17.6%, 总烯烃收率达14.8%, 且经过12 h的脱氢反应后, 催化剂性能无明显的衰减。通过对这些碳材料的化学结构和催化性能的对比分析, 发现N掺杂和B掺杂使得碳材料表面的大量C-O基团转变为具有丙烷脱氢活性的C=O基团, 抑制反应过程中的C-C键断裂, 从而提高目标产物丙烯的选择性。生物质碳材料成本低廉且来源广泛, 以其作为催化剂可以极大地推动丙烷脱氢工业的发展。     

The degradation of landfill leachate in the presence of different catalysts by sonolytic and sonocatalytic processes

In the study, the degradation of landfill leachate by single ultrasound (sonolytic) and sonolytic combined with Fe²⁺ and TiO₂ catalysts was carried out in laboratory conditions. The effect of pH and ultrasonic wave amplitude was also investigated in terms of color removal, total organic carbon (TOC) and chemical oxygen demand (COD) from leachate by the sonolytic degradation process. In this process, the color removal efficiency was recorded as 81.81% at 620?nm, pH?=?2.0 and 70% wave amplitude. The sonocatalytic degradation of landfill leachate accompanied by different catalysts was studied by using the 70% wave amplitude at pH?=?2.0 and room temperature for 20?min. The sonocatalytic degradation of leachate by using Fe²⁺ and TiO₂ was found to be significantly higher than sonolytic degradation (p?2+ concentration increased from 1.0 to 3.0?mg/L, the COD and color removal of leachate significantly decreased (p?相似文献   

Effect of nitric acid modification on the lead(II) adsorption of mesoporous biochars with different mesopore size distributions

Two mesoporous biochars AC-1 and AC-2 with similar chemical properties but different mesopore size distributions were prepared to study the effect of HNO₃ modification on the lead(II) adsorption. AC-2 possesses higher mesopore volume and broader pore diameter than AC-1, while their surface area and micropore volume are similar. Adsorption experiments showed that AC-2 had far better removal efficiency, indicating the important role of mesopores played in the adsorption. HNO₃ modification enhanced the adsorption capacity of lead AC-1 and AC-2 by 15 and 27 mg g^?1, respectively. In particular, the removal rate of lead for AC-1 was improved from 46 to 99 % by HNO₃ treatment at a low initial lead concentration of 10 mg L^?1. Results of Boehm’s titration demonstrated that the amounts of oxygenic acid groups of AC-1 and AC-2 increased to 2.456 and 2.705 mmol g^?1 after HNO₃ treatment, respectively. Analyses of FTIR spectrum revealed that AC-2 was more likely to graft oxygen-containing acidic functional groups than AC-1, indicating that higher mesoporosity takes advantage of grafting more oxygenic functional groups, thus forming more active adsorption sites. The above results indicate that mesoporous biochars with wider pore width are more favorable to be introduced with oxygenic groups for enhanced lead removal efficiency.     

Iron removal from human plasma based on molecular recognition using imprinted beads

The aim of this study is to prepare ion-imprinted polymers which can be used for the selective removal of Fe³⁺ ions from Fe³⁺-overdosed human plasma. N-Methacryloly-(l)-glutamic acid (MAGA) was chosen as the complexing monomer. In the first step, Fe³⁺ was complexed with MAGA and the Fe³⁺-imprinted poly(HEMA–MAGA) beads were synthesized by suspension polymerization. After that, the template (i.e., Fe³⁺ ions) was removed using 0.1 M EDTA solution. The specific surface area of the Fe³⁺-imprinted poly(HEMA–MAGA) beads was found to be 76.4 m²/g with a size range of 63–140 μm in diameter and the swelling ratio was 75%. According to the elemental analysis results, the beads contained 84.7 μmol MAGA/g polymer. The maximum adsorption capacity was 92.6 μmol Fe³⁺/g beads. The relative selectivity coefficients of imprinted beads for Fe³⁺/Zn²⁺ and Fe³⁺/Cr³⁺ were 17.3 and 48.6 times greater than non-imprinted matrix, respectively. The Fe³⁺-imprinted poly(HEMA–MAGA) beads could be used many times without decreasing their adsorption capacities significantly.     

Nanocellulose fibers for biosorption of cadmium,nickel, and lead ions from aqueous solution

Nanocellulose fibers were prepared using physico-chemical treatment of rice straw, characterized and explored for the remediation of some toxic metals from wastewater. Nanocellulose fibers were found to have long rod-like elongated nano fibrillated morphology with average grain size 6 nm. The prepared nanocellulose fibers (0.5 g) in batch experiments showed removal efficiency of 9.7 mg/g Cd (II), 9.42 mg/g Pb(II), and 8.55 mg/g Ni (II) ions from 25 mg/l of metal solution. The sorption process fitted well to both Freundlich and Langmuir isotherms [(R²) Cd (II): 0.92, 0.95; Pb(II): 0.94, 0.97 and Ni (II): 0.97, 0.98]. The regeneration studies signify that nanocellulose fibers can be successively used up to three cycles of regeneration. Nanotech reinforcement to native cellulose significantly enhanced metal removal efficiency compared to rice straw and cellulose fibers, provides new avenues as cost effective, environment-friendly green remediation or can be used as a pre-treatment step prior to chemical decontamination methods for toxic metals.     

Crystallographic and magnetic properties of Fe-doped SnO<Subscript>2</Subscript> nanopowders obtained by a sol–gel method

We prepared Sn_1?x Fe _x O₂ (x = 0, 0.03, 0.05, 0.10, and 1.0) nanoparticles by the polymeric precursor method based on the modified Pechini process. Two types of starting reactants for both tin and iron were explored: Sn(II)/Fe(II) and Sn(IV)/Fe(III) precursors. Thermogravimetric analysis revealed that the precursor powders prepared from Sn(IV) have higher excess in ethylene glycol in comparison to precursor samples prepared from Sn(II). XRD patterns for those samples prepared from Sn(IV) and Fe(III) were adequately fitted by introducing only the cassiterite phase of SnO₂. Micro-Raman spectra also support these findings, and additionally it is found that the presence of iron broadened and reduced the intensities of the principal bands. ¹¹⁹Sn Mössbauer spectra indicated only the presence of Sn⁴⁺, whereas RT ⁵⁷Fe Mössbauer spectra suggested the presence of two Fe³⁺ sites located at different distorted sites. On the other hand, micro-Raman and ⁵⁷Mössbauer spectrometry showed the formation of hematite as impurity phase for those samples with iron concentrations above ~5 at.%, prepared from Fe(II) and Sn(II) precursors. In addition, their XRD patterns revealed larger average grain sizes for the cassiterite phase of SnO₂ in comparison to those samples prepared from Sn(IV) and Fe(III).     

Fe2+‐Doped Layered Double (Ni,Fe) Hydroxides as Efficient Electrocatalysts for Water Splitting and Self‐Powered Electrochemical Systems

Developing nonprecious electrocatalysts with superior activity and durability for electrochemical water splitting is of great interest but challenging due to the large overpotential required above the thermodynamic standard potential of water splitting (1.23 V). Here, in situ growth of Fe²⁺‐doped layered double (Ni, Fe) hydroxide (NiFe(II,III)‐LDH) on nickel foam with well‐defined hexagonal morphology and high crystallinity by a redox reaction between Fe³⁺ and nickel foam under hydrothermal conditions is reported. Benefiting from tuning the local atomic structure by self‐doping Fe²⁺, the NiFe(II,III)‐LDH catalyst with higher amounts of Fe²⁺ exhibits high activity toward oxygen evolution reaction (OER) as well as hydrogen evolution reaction (HER) activity. Moreover, the optimized NiFe(II,III)‐LDH catalyst for OER (O‐NiFe(II,III)‐LDH) and catalyst for HER (H‐NiFe(II,III)‐LDH) show overpotentials of 140 and 113 mV, respectively, at a current density of 10 mA cm^?2 in 1 m KOH aqueous electrolyte. Using the catalysts for overall water splitting in two‐electrode configuration, a low overpotential of just 1.54 V is required at a benchmark current density of 10 mA cm^?2. Furthermore, it is demonstrated that electrolysis of the water device can be drived by a self‐powered system through integrating a triboelectric nanogenerator and battery, showing a promising way to realize self‐powered electrochemical systems.     

Preparation of doped TiO2 nanofiber membranes through electrospinning and their application for photocatalytic degradation of malachite green

Fe³⁺ doped TiO₂ composite nanofiber membranes and pure TiO₂ nanofiber membranes were prepared through electrospinning, and were applied to the photocatalytic degradation of malachite green (MG) in aqueous solutions under simulated sunlight. The effects of ferric ion content, initial concentration of MG, photocatalyst loading, and recycling behavior were studied. Microscopic characterization showed that the products have fiber morphology with bent property and favorable continuity. The degradation results showed that TiO₂ nanofiber membranes containing 0.8 mol% Fe³⁺ performed the best photocatalytic activity against MG under identical light irradiation. The TiO₂:Fe³⁺ composite nanofiber membranes maintained their photocatalytic efficiency through seven recycling processes.     

Perchlorate removal in Fe0/H2O systems: Impact of oxygen availability and UV radiation

In this study, the removal of perchlorate (0.016 mM ) using Fe⁰-only (325 mesh, 10 g L⁻¹) and Fe⁰ (10 g L⁻¹) with UV (254 nm) reactions were investigated under oxic and anoxic conditions (nitrogen purging). Under anoxic conditions, only 2% and 5.6% of perchlorate was removed in Fe⁰-only and Fe⁰/UV reactions, respectively, in a 12 h period. However, under oxic conditions, perchlorate was removed completely in the Fe⁰-only reaction, and reduced by 40% in the Fe⁰/UV reaction, within 9 h. The pseudo-first-order rate constant (k₁) was 1.63 × 10⁻³ h⁻¹ in Fe⁰-only and 4.94 × 10⁻³ h⁻¹ in Fe⁰/UV reaction under anoxic conditions. Under oxic conditions, k₁ was 776.9 × 10⁻³ h⁻¹ in Fe⁰-only reaction and 35.1 × 10⁻³ h⁻¹ in the Fe⁰/UV reaction, respectively. The chlorine in perchlorate was recovered as chloride ion in Fe⁰-only and Fe⁰/UV reactions, but lower recovery of chloride under oxic conditions might due to the adsorption/co-precipitation of chloride ion with the iron oxides. The removal of perchlorate in Fe⁰/UV reaction under oxic conditions increased in the presence of methanol (73%, 9 h), a radical scavenger, indicating that OH radical can inhibit the removal of perchlorate. The removal of perchlorate by Fe⁰-only reaction under oxic condition was highest at neutral pH. Application of the Langmuir-Hinshelwood model indicated that removal of perchlorate was accelerated by adsorption/co-precipitation reactions onto iron oxides and subsequent removal of perchlorate during further oxidation of Fe⁰. The results imply that oxic conditions are essential for more efficient removal of perchlorate in Fe⁰/H₂O system.     

Synthesis of magnetic crosslinked starch-graft-poly(acrylamide)-co-sodium xanthate and its application in removing heavy metal ions

ABSTRACT

This paper describes the synthesis and characterisation of a magnetic crosslinked starch-graft-poly(acrylamide)-co-sodium xanthate (M-CSAX) nanocomposite based on magnetic starch (MCS), acrylamide (AM) and sodium xanthate that underwent heavy metal ions removal in response to an external magnetic field. The material was prepared using magnetic particle Fe₃O₄ nanoflakes (NFs) together with vinylated starch and poly(acrylamide)-co-sodium xanthate via an ultrasound-assisted radical crosslinking/polymerisation reaction. MCS was synthesised by a direct compounding method using Fe₃O₄ NFs as nuclear and vinylated starch as shell. The obtained M-CSAX has a saturation magnetisation value of 19.21 emu·g^?1. Flocculation experiment results showed that the composites have functions of removing both turbidity and heavy metal ions from aqueous solution, and can adsorb 78.3% of Pb²⁺ and 63% of Cu²⁺ from the corresponding salt solutions. The findings of the present work highlight the potential for using M-CSAX as an effective and recyclable adsorbent for wastewater treatment.     

Ferromagnetism in Fe-doped tetra-needle like ZnO whiskers

The Fe-doped tetra-needle like ZnO whiskers (T-ZnOw) were prepared with different loadings of Fe³⁺ by a solid solution process. The structures and magnetic properties of the samples were characterized by using X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometer, respectively. The results indicate that Fe³⁺ ions are successfully doped into the crystal lattice of T-ZnOw matrix. The second phase of ZnFe₂O₄ is formed by heavy doping of Fe³⁺ ions, and the solid solubility limit of Fe³⁺ in T-ZnOw crystal is about 0.7 mol%. The magnetic properties reveal that some of the Fe-doped T-ZnOw exhibits room-temperature ferromagnetic behaviors. The room-temperature ferromagnetism in the Fe-doped T-ZnOw system is ascribed to be originated from the change of the electronic states of ZnOw caused by irons doping.