Removal of lead (II) and nickel (II) ions from aqueous solution using activated carbon prepared from rapeseed oil cake by Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> activation

In this study, rapeseed oil cake as a precursor was used to prepare activated carbons by chemical activation with sodium carbonate (Na₂CO₃) at 600 and 800 °C. The activated carbon with the highest surface area of 850 m² g^?1 was produced at 800 °C. The prepared activated carbons were mainly microporous. The activated carbon having the highest surface area was used as an adsorbent for the removal of lead (II) and nickel (II) ions from aqueous solutions. The effects of pH, contact time, and initial ion concentration on the adsorption capacity of the activated carbon were investigated. The kinetic data of adsorption process were studied using pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model. The experimental data were well adapted to the pseudo-second-order model for both tested ions. The adsorption data for both ions were well correlated with Langmuir isotherm. The maximum monolayer adsorption capacities of the activated carbon for the removal of lead (II) and nickel (II) ions were determined as 129.87 and 133.33 mg g^?1, respectively.     

Adsorption kinetics, isotherm, and thermodynamics of Hg2+ to polyaniline/hexagonal mesoporous silica nanocomposite in water/wastewater

A nanocomposite of polyaniline/hexagonal mesoporous silica (PAN/HMS) was prepared and characterized by BET analysis, transmission electron microscopy, and FT-IR spectra. Batch adsorption results showed that PAN/HMS had high affinity to Hg²⁺ in aqueous solutions. Various factors affecting the adsorption capacity such as contact time, temperature, absorbent dosage, pH, and initial concentration of Hg²⁺ ions were investigated. The adsorption kinetics for the Hg²⁺ showed that the adsorption reached equilibrium within 8 min and adsorption rates followed the pseudo-second-order rate law, indicating chemical sorption as the rate-limiting step of the adsorption mechanism. Sorption of Hg²⁺ to PAN/HMS agreed well to the Langmuir adsorption model at different ionic strengths with the maximum adsorption capacity of 843 mg g^?1 (I = 1000 mg L^?1) at pH 10. Thermodynamic studies revealed that the adsorption of Hg²⁺ ions was spontaneous, exothermic processes with an increase of entropy. The recovery of the Hg²⁺ from the adsorbent was found to be more than 88 % using H₂SO₄ (0.1 M), and the ability of the absorbent to be reused was investigated.     

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.     

Novel mesoporous Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript>/CTAB–SiO<Subscript>2</Subscript> as an effective adsorbent for the removal of amoxicillin and tetracycline from water

The current study was carried out to investigate the efficiency of using magnetic mesoporous of cetyltrimethylammonium bromide-functionalized silica-coated magnetite for removing amoxicillin (AMX) and tetracycline (TC) from tap water, river water, and medical wastewater as real samples. The properties of the synthesized adsorbent were characterized through transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, pH_pzc, and also Brunauer, Emmett, and Teller (BET) methods. The BET surface area and the average diameter of mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ in accordance with TEM were 157.8 m² g^?1 and around 55 nm, respectively. In batch tests, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength, and adsorbent dose, were analysed. The experimental adsorption data were modelled using different classical and recently developed models. According to the results, the maximum adsorption capacities of AMX and TC on mesoporous Fe₃O₄/SiO₂/CTAB–SiO₂ were found to be 362.66 and 220.70 mg g^?1, respectively. Also, the results indicated that AMX and TC loaded on the adsorbent could be easily desorbed with 0.1 mol L^?1 HNO₃⁺ acetonitrile (1:1, v/v) and the adsorbent showed good reusability for the adsorption of the drugs studied.     

Efficient desulfurization of fuel with functionalized mesoporous carbon CMK-3-O and comparison its performance with mesoporous carbon CMK-3

In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO₃ aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N₂ adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g^?1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L^?1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g^?1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles.     

High surface area ordered mesoporous carbon for high-level removal of rhodamine B

We report the synthesis of ordered mesoporous carbons (OMCs) with high surface area by the variation of mass ratio of tetraethylorthosilicate (TEOS) to resol, followed by carbonization and removal of silica. The obtained OMCs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ adsorption and desorption analysis, Zeta potential and Fourier transform infrared spectroscopy. Results reveal that the OMCs were transformed from ordered to disordered structure at high mass ratio of TEOS/resol. A typical sample of OMCs possesses very high specific surface area of 1906 m² g^?1 and large pore volume of 1.8 cm³ g^?1. The OMCs as adsorbent show an ultrahigh-level adsorption capacity for the removal of toxic dye Rhodamine B (1028 mg g^?1) in the short contact time (60 min). The adsorption follows pseudo second-order kinetics with rate constant 2.5 × 10^?4 g mg^?1 min^?1, showing rapid adsorption properties. The OMCs can be reused; though the adsorption capacity seems to decrease somewhat after each cycle tested over 10 reuse cycles, it might be affected by the chemisorptions. The adsorption mechanism study reveals that the adsorption proceeds with hydrogen bonding between hydrogen atom of carboxylic group at OMCs and electronegative element (nitrogen) of RhB. It is concluded that the surface area and pore volume of the OMCs is tuned by the variation of mass ratio of TEOS to resol which is also demonstrated to have ultrahigh adsorption capacity for the model RhB dye.     

Capture and reversible storage of volatile iodine by porous carbon with high capacity

The capture of iodine using porous materials has attracted considerable interest. In this work, porous carbon with a special surface area of 1973 m² g^?1 was prepared by simple activation method. As an adsorbent, the adsorption capacity of the resulting porous carbon could reach up to 376 wt% for iodine vapor and 460 mg g^?1 for iodine uptake in cyclohexane, which both are among the highest values reported up to now. Taking advantages of its high special surface area, easy preparation, low cost, as well as good regeneration, the resulting porous carbon shows great potential in the removal of radioactive iodine at different states.     

Experimental and modelling studies of carbon dioxide adsorption by porous biomass derived activated carbon

The goal of the study was to produce a low-cost activated carbon from agricultural residues via single stage carbon dioxide (CO₂) activation and to investigate its applicability in capturing CO₂ flue gas. The performance of the activated carbon was characterized in terms of the chemical composition, surface morphology as well as textural characteristics. The adsorption capacity was investigated at three temperatures of 25, 50 and 100 °C for different types of adsorbate, such as purified carbon dioxide and binary mixture of carbon dioxide and nitrogen. The purified CO₂ adsorption study showed that the greatest adsorption capacity of the optimized activated carbon of 1.79 mmol g^?1 was obtained at the lowest operating temperature. In addition, the adsorption study proved that the adsorption capacity for binary mixtures was lower due to the reduction in partial pressure. The experimental values of the purified CO₂ adsorption were modelled by the Lagergren pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion model. Based on the analysis, it inferred that the adsorption of CO₂ followed the pseudo-second-order model with regression coefficient value higher than 0.995. In addition, the adsorption study was governed by both film diffusion and intra-particle diffusion. The activation energy that was lesser than 25 kJ mol^?1 implied that physical adsorption (physisorption) occurred.     

Synthesis,Characterization, and Cesium Sorption Performance of Potassium Nickel Hexacyanoferrate-Loaded Granular Activated Carbon

GAC has been modified by loading of potassium nickel hexacyanoferrate (KNiCF) as a new adsorbent for cesium adsorption. The potassium nickel hexacyanoferrate-loaded granular activated carbon (KNiCF-GAC) was characterized using powder x-ray diffraction (XRD) and nitrogen adsorption-desorption isotherm data, infrared spectroscopy, and its cesium adsorption performance in aqueous solution was investigated. The effect of the various parameters such as initial pH value of the solution, contact time, temperature, and initial concentration of the cesium ion on the adsorption efficiencies of KNiCF-GAC have been studied systematically by batch experiments. The adsorption isotherm of KNiCF-GAC was studied and the fitted results indicated that the Langmuir model could well represent the adsorption process. The maximum adsorption capacity of Cs⁺ onto KNiCF-GAC was found to be 163.9 mg · g^?1.     

Synthesis of a mesoporous carbon from peach stones for adsorption of basic dyes from wastewater: kinetics,modeling, and thermodynamic studies

The objective of this work was to evaluate the efficiency of a synthesized activated carbon for the removal of methylene blue from aqueous solution. Activated carbons synthesized from agricultural wastes precursors are an interesting alternative for their use as adsorbents and catalyst supports in the wastewater treatment field, and represent an important ecological benefit. In this work, mainly, mesoporous-activated carbon was synthesized from peach stones by chemical activation. The textural, morphological, and chemical characterizations of the material were carried out, revealing the acidic nature of the solid. The effects of different experimental conditions on the adsorption capacity, initial methylene blue concentration, pH solution, adsorbent dosage, and temperature have been investigated. The kinetic experimental data followed the pseudo-second-order model. Intra-particle diffusion model indicated that the adsorption process is controlled by intra-particle diffusion stage. Adsorption isotherms were conducted at several operation temperatures, obtaining the largest methylene blue adsorption capacity value, 444.3 mg g^?1, at the highest temperature, 333 K. The equilibrium adsorption data were tested by four isotherm models, i.e., Langmuir, Freundlich, Tóth, and Redlich–Peterson. It was found that the adsorption data fitted better to Tóth and Redlich–Peterson isotherm models. The calculated thermodynamic parameters suggested that an endothermic and spontaneous process is occurring.     

Isotherm,kinetic, and thermodynamic studies on the adsorption behavior of malachite green dye onto montmorillonite clay

ABSTRACT

Systematic batch mode studies of adsorption of malachite green (MG) on montmorillonite clay were carried out as a function of process parameters which include pH, adsorbent dosage, agitation speed, ionic strength, initial MG concentration, and temperature. Montmorillonite was found to have excellent adsorption capacity. Equilibrium adsorption isotherms were measured for the single-component system, and the experimental data were analyzed by using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. It was found that the Langmuir equation appears to fit the equilibrium data. The monolayer (maximum) adsorption capacity (q_m) was found to be 262.494 mg g^?1 for montmorillonite. The experimental kinetic data were analyzed using the first-order, second-order, Elovich, and intraparticle kinetic models and the second-order kinetic model described the adsorption kinetics accurately for MG. Thermodynamic activation parameters such as ΔG*, ΔS*, and ΔH* of the adsorption of MG on montmorillonite were also calculated.     

Synthesis of new activated carbons produced from polymer waste

In this study activated carbons were prepared from polymer waste, which is side product and waste in textile industry; by chemical activation with KOH. The influence of chemical ratio onto pore structure was investigated. Activation temperature was selected as 800°C. The impregnated sample was raised to the activation temperature under N₂ (100 mL. min^?1) atmosphere with 10°C. min^–1 heating rate and hold at this temperature for 1 h. Determined BET surface area were in the range of 817–1889 m²·g^–1. Impregnation ratio; 5:1 was found to be the optimal condition for producing high surface area carbons with KOH activation. Activated carbon samples and raw material were characterized by Boehm titration, XRD, FT-IR, DTA and TGA. Adsorption capacity for selected model compound, such as naproxen sodium, caffeine and tannic acid, has been investigated.     

Optimization study of adsorption parameters for removal of phenol on gastropod shell dust using response surface methodology

Phenolics have recently been of great concern because of the extreme toxicity and persistence in the environment. This study explores the possibility of using gastropod shell dust (GPSD) to remove phenol from aqueous solutions. The removal of phenol was investigated in batch mode. The influence of different experimental parameters—initial pH, adsorbent dose, initial concentration, contact time, stirring rate, temperature, and their interaction during phenol adsorption—were determined by response surface methodology based on three-level four-factorial Box–Behnken design. Optimized values of initial phenol concentration, pH, adsorbent dose, and contact time were found as 10.16 mg/L, 4.22, 0.50 g/L, and 33.47 min, respectively. The experimental equilibrium data were tested by four widely used isotherm models namely, Langmuir and Freundlich, D–R, and Temkin. It was found that adsorption of phenol on gastropod shell dust correlated with the Langmuir isotherm model, implying monolayer coverage of phenol onto the surface of the adsorbent. The maximum adsorption capacity was found to be 56.89 mg g^?1 at 333 K. Regeneration study revealed that about 92 % phenol can be regenerate within 90 min from the spent GPSD. Kinetics of the adsorption process was tested by pseudo-first-order, pseudo-second-order kinetics, and intra-particle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model. Intra-particle diffusion was not the sole rate-controlling factor. The activation energy of the adsorption process (E _a) was found to be 2.68 kJ mol^?1, indicating physisorption nature of phenol adsorption onto gastropod shell dust. A thermodynamic study showed spontaneous nature and feasibility of the adsorption process. A negative enthalpy (ΔH°) value indicated that the adsorption process was exothermic. The results revealed that gastropod shell dust can be used as an effective and low-cost adsorbent to remove phenol from aqueous solutions.     

High Adsorption Capacity of Multi-Walled Carbon Nanotube as Efficient Adsorbent for Removal of Al(III) from Wastewater

Multi-walled carbon nanotubes (MWCNTs) were oxidized for removal of Al(III) from aqueous solution through batch experiment. The effect of pH, adsorbent dosage, contact time, and temperature on the adsorption was investigated. The optimum pH for adsorption of Al(III) was found to be 4.0. The adsorption kinetic of Al(III) onto COOH-MWCNTs fitted with the pseudo-second-order model and the experimental results showed good correlation with the Langmuir model. The maximum adsorption capacity for Al(III) was obtained as 104.16 mg g^?1.     

Adsorption kinetics and surface modeling of aqueous methylene blue onto activated carbonaceous wood sawdust

In this work, Sawdust was used to develop a new low-cost adsorbent and study its application to remove methylene blue dye from aqueous solution. Sawdust was calcined under air atmosphere at three different temperatures (300°C, 400°C, and 500°C) using phosphoric acid (H₃PO₄) as an activating agent. The structure, morphology, surface functions and the chemical composition of adsorbent were characterized by Fourier Transform Infrared spectra (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), specific surface area (BET) and Boehm method. Different operational parameters such as pH, adsorbent loading, contact time and were investigated to evaluate experimental data. The adsorption of MB on SD-300, SD-400, and SD-500 show that the pseudo-second-order and Langmuir models fitted better the experimental results of MB adsorption onto all adsorbents. The maximum capacities based on the Langmuir model were 416.7 mg.g^?1 for SD-300, 526.3 mg.g^?1 for SD-400, and 819.7 mg.g^?1 for SD-500. The positive values of ΔG, ΔH, and ΔS implied that the adsorption process was non-spontaneous and endothermic nature. Finally, Regeneration of the SD-500 was investigated and optimization was performed using CCD combined with RSM.     

Biosorption of heavy metals and cephalexin from secondary effluents by tolerant bacteria

The biosorption of heavy metal ions and the antibiotic cephalexin from secondary effluents by the cell biomass of tolerant bacterial strains was investigated in this article. A total of 67 bacterial strains were isolated from a secondary effluents generated by sewage treatment plants. These strains were adapted to tolerate 6 mM nickel ions (Ni²⁺) and 10 g L^?1 cephalexin. Bacterial cell biomass that has more than 150 mg g^?1 biosorptive capacity was used for the biosorption under optimal conditions. The biosorption process was efficient in removing heavy metals: 87.63 % of cadmium, 74.61 % of copper, 58.32 % of nickel, 61.9 % of lead, and 94.26 % of zinc, respectively. The maximum biosorptive capacity of the bacterial cell biomass for cephalexin was 60 mg g^?1. The efficiency of cephalexin biosorption was reduced by more than 40.83 and 82.88 % (living and dead cells, respectively) in the presence of 1 mg L^?1 Ni²⁺ ions compared with the control, whereas no biosorption by dead cell biomass was recorded in aqueous solutions contaminated with cadmium, zinc, copper, and lead ions. In conclusion, biosorption which efficiently removes metal ions, but not cephalexin, from secondary effluents is explained.     

Adsorption of Thorium from Aqueous Solution using Nanoporous Adsorbents: Effect of Contact Time,pH, Initial Concentration,and Temperature

Nanoporous silicates MCM-41 have been prepared using different surfactants such as cetyltrimethylammonium bromide (C₁₆TAB) and dodecyltrimethylammonium bromide (C₁₂TAB) as template. The adsorbents are characterized using powder x-ray diffraction, nitrogen adsorption-desorption isotherm data, scanning electron microscopy, and transmission electron microscopy. The thorium sorption was studied as a function of shaking time, pH, initial concentration, and temperature. The sorption of thorium at the determined optimum conditions follows Langmuir and Freundlich isotherms. The results show that the nanoporous MCM-41 synthesized by C₁₂TAB has more adsorption capacity than the MCM-41 synthesized by C₁₆TAB (77.6 µmol · g^?1 vs. 52.1 µmol · g^?1) at 25°C. Th(IV) adsorption onto nanoporous adsorbents was very fast process and therefore, this adsorbent is suitable for column separation. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were found to be 47.76 KJ · mol^?1, 196.21 J · mol^?1 · K^?1, and 19.00 KJ · mol^?1, respectively (at 298 K). The positive value ΔH° suggested the endothermic nature of adsorption and negative ΔG° indicates the feasibility and spontaneity of the adsorption process.     

Flexible carbon@graphene composite cloth for advanced lithium–sulfur batteries and supercapacitors with enhanced energy storage capability

Flexible carbon@graphene composite cloth was fabricated, and the resultant composite cloth consists of core–shell hollow structured carbon/graphene hybrid fibers with abundant micro- and mesoporosity and hydrophilic functionality. These unique features enable the composite cloth to be a promising material for energy storage application. As an efficient polysulfide adsorbent, the composite can be applied in lithium–sulfur batteries by being sandwiched between the sulfur cathode and polymeric separator. With this novel configuration, a high reversible capacity of ca. 900 mAh g^?1 and excellent cycle-life has been achieved, which is ascribed to the excellent polysulfides adsorption and confinement capability of the special core–shell and hollow structured porous hybrid fibers. Additionally, the composite cloth can be applied in supercapacitors as a flexible binder-free electrode, exhibiting a high specific capacitance of 271 F g^?1 (360 F cm^?3) at 0.1 A g^?1 in 6 M KOH, as well as excellent rate capability and cycling stability. The assembled symmetric supercapacitor supplies a high energy density of up to 9.4 Wh kg^?1 (12.5 Wh L^?1) with a power density of 25.0 W kg^?1 (33.3 W L^?1) and remains 5.7 Wh kg^?1 (7.6 Wh L^?1) with 4.5 kW kg^?1 (6.0 kW L^?1).     

Removal of Methylene Blue by Activated Carbon Prepared from Waste in a Fixed-Bed Column

In this study, the ability of activated carbon prepared from waste to adsorb methylene blue from aqueous solution was investigated in a fixed-bed column. The effect of flow rate and inlet methylene blue concentration on the adsorption characteristics of activated carbon was investigated at 25°C. Freundlich and Langmuir adsorption models have been used to represent the column equilibrium data. The Langmuir constants of Q_o and b were determined as 6.38 mg · g^?1 and 0.34 L · mg^?1, respectively. The results showed that the equilibrium data fitted Langmuir isotherm within the concentration range studied. Four kinetic models, Adams-Bohart, Wolborska, Thomas, and Yoon-Nelson, were applied to experimental data to predict the break-through curves and determine the characteristic parameters of the column useful for process design. Results also indicate that the adsorption process can only deal with lower flow rates and lower concentrations of methylene blue solution if a high percentage of removal is required for extended periods. All models were found suitable for methylene blue adsorption onto activated carbon.     

Centrifugal melt spinning of polyvinylpyrrolidone (PVP)/triacontene copolymer fibres

Polyvinylpyrrolidone/1-triacontene (PVP/TA) copolymer fibre webs produced by centrifugal melt spinning were studied to determine the influence of jet rotation speed on morphology and internal structure as well as their potential utility as adsorbent capture media for disperse dye effluents. Fibres were produced at 72 °C with jet head rotation speeds from 7000 to 15,000 r min^?1. The fibres were characterised by means of SEM, XRD and DSC. Adsorption behaviour was investigated by means of an isothermal bottle point adsorption study using a commercial disperse dye, Dianix AC-E. Through centrifugal spinning nanofibers and microfibers could be produced with individual fibres as fine as 200–300 nm and mean fibre diameters of ca. 1–2 µm. The PVP/TA fibres were mechanically brittle with characteristic brittle tensile fracture regions observed at the fibre ends. DSC and XRD analyses suggested that this brittleness was linked to the graft chain crystallisation where the PVP/TA was in the form of a radial brush copolymer. In this structure, the triacontene branches interlock and form small lateral crystals around an amorphous backbone. As an adsorbent, the PVP/TA fibres were found to adsorb 35.4 mg g^?1 compared to a benchmark figure of 30.0 mg g^?1 for a granular-activated carbon adsorbent under the same application conditions. PVP/TA is highly hydrophobic and adsorbs disperse dyes through the strong “hydrophobic bonding” interaction. Such fibrous assemblies may have applications in the targeted adsorption and separation of non-polar species from aqueous or polar environments.