Potential Sorbent Research Articles

Waste Brick Dust as Potential Sorbent of Lead and Cesium from Contaminated Water.

Adsorption properties of waste brick dust (WBD) were studied by the removing of PbII and CsI from an aqueous system. For adsorption experiments, 0.1 M and 0.5 M aqueous solutions of Cs+ and Pb2+ and two WBD (Libochovice—LB, and Tyn nad Vltavou—TN) in the fraction below 125 µm were used. The structural and surface properties of WBD were characterized by X-ray diffraction (XRD) in combination with solid-state nuclear magnetic resonance (NMR), supplemented by scanning electron microscopy (SEM), specific surface area (SBET), total pore volume and zero point of charge (pHZPC). LB was a more amorphous material showing a better adsorption condition than that of TN. The adsorption process indicated better results for Pb2+, due to the inner-sphere surface complexation in all Pb2+ systems, supported by the formation of insoluble Pb(OH)2 precipitation on the sorbent surface. A weak adsorption of Cs+ on WBD corresponded to the non-Langmuir adsorption run followed by the outer-sphere surface complexation. The leachability of Pb2+ from saturated WBDs varied from 0.001% to 0.3%, while in the case of Cs+, 4% to 12% of the initial amount was leached. Both LB and TN met the standards for PbII adsorption, yet completely failed for any CsI removal from water systems.

Adsorption of Fe(II) Ions from Aqueous Solution Using Silica-Supported Organic–Inorganic Hybrid Sorbents

A silica-supported organic–inorganic hybrid sorbents were prepared by sol–gel method and characterized by Fourier transmission infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry and thermal analysis. The adsorption behaviors of Fe(II) ions onto the hybrid sorbents from aqueous media had been investigated. The adsorption capacity of hybrid sorbents for Fe(II) ions was 90.7 mg g−1. Adsorption equilibrium of Fe(II) ions was achieved within 30 min of contact time. Solution pH had a minor effect on Fe(II) ions adsorption in the range of pH 3–6. The highly selective binding of the hybrid sorbents for Fe(II) ions with respective to other competitor ions (such as Cd(II), Zn(II), Co(II), Ni(II), and Pb(II) ions) was due to the high complexation affinity between Fe(II) ions and cyano groups. The adsorption/desorption cycle of hybrid sorbent could be up to three times. Experimental data revealed that Langmuir isotherm and pseudo–second–order models give best fit for Fe(II) ions adsorption with high correlation coefficients (>0.99). The calculation of thermodynamic parameters showed that the adsorption of Fe(II) ions on the hybrid sorbents was an exothermic and spontaneous process. These results confirmed that the hybrid sorbent could be a potential sorbent for the removal of Fe(II) ions from aqueous solutions.

Natural aluminosilicate clay obtained from south-eastern Nigeria as potential sorbent for oil spill remediation

Few reports exist on the use of natural inorganic sorbents such as clays compared to organic biomass materials for crude oil sorption. Also, the mechanistic kinetic, isotherm and thermodynamics have seldom been discussed in the few clay oil sorption studies available. This work evaluated the use of Natural Clay (NC) for removal of crude oil from solution. The sorbent was characterized by the Fourier transform infrared, scanning electron microscope, X-ray diffraction, X-ray fluorescence and Brunauer-Emmett-Teller surface area analyzer. The chemical oxide composition revealed SiO2 (53.1%) and Al2O3 (19.8%) as major components of NC and cation exchange capacity of 76.1 mEq/100 g. The Langmuir model presented the best fit with higher R2 of 0.981 and lower Sum square error (SSE) of 0.21 compared to the Freundlich and Tempkin isotherm. The pseudo-first order model was found to be applicable compared to the pseudo-second order kinetic analysis, with intra-particle diffusion mechanism involved in the removal process. Thermodynamics revealed a spontaneous, endothermic and physical sorption of crude oil on NC. The sorption capacity of NC for crude oil was found to be higher than most sorbents reported in literature. NC showed good regeneration and reusability for crude oil removal using n hexane after three cycles of sorption-desorption experiment The study indicated enormous potentials of NC as low cost sorbent for oil spill treatment.

Preparation of pineapple waste-derived porous carbons with enhanced CO2 capture performance by hydrothermal carbonation-alkali metal oxalates assisted thermal activation process

The pineapple waste-derived porous carbons with enhanced CO2 adsorption performance were successfully prepared by a facile hydrothermal carbonation and followed thermal activation using facile alkali metal oxalates instead of KOH or K2CO3 for chemical activation. Compared with macroporous-mesoporous carbons activated by Li2C2O4 and Na2C2O4, the microporous carbon activated by K2C2O4 at 700 °C with a relatively high specific surface area of 1076.3 m2 g−1 and big pore volume of 0.92 cm3 g-1 for narrow micropores (<1 nm)for narrow micropores (<1 nm) shows the highest adsorption capacities of 5.32 mmol g-1 at 0 °C, and 4.25 mmol g-1 at 25 °C under 1 bar, respectively. Furthermore, all the samples show high selectivities from 18.24 to 38.42 for CO2/N2 separation, stable cyclic capability with adsorption loss of 12.6–17.8% after twelve cycles at 25 °C and reasonable isosteric heat of CO2 adsorption. Especially, the microporous carbon activated by facile K2C2O4 at 700 °C shows speedy adsorption dynamics and excellent dynamic adsorption performance for simulated flue gas based on its breakthrough curve. In combination with the low-cost carbon source, the above advantages make the pineapple waste-derived porous carbons exceptionally potential sorbent to capture and separate CO2 under real conditions.

Enhanced CO2 sorption capacity of amine-tethered fly ash residues derived from co-firing of coal and biomass blends

Co-firing of coal and biomass blends provides a promising route for clean energy utilization with high efficiency and mitigated pollutants emission. However, the technology meets an important challenge in effective utilization of the co-firing fly ashes. Efforts have been made to valorize the co-firing fly ash residues as potential CO2 sorbents. To achieve enhanced CO2 sorption performance, the samples were modified with tetraethylenepentamine (TEPA). Effects of amine loading, CO2 sorption temperature, initial CO2 concentration and gas flow rate on CO2 sorption behaviors of the amine-tethered sorbents were investigated. The desired sorbent with 25% TEPA loading presented the highest CO2 sorption capacity of 1.19 mmol CO2/g when tested under 60 °C and 15%CO2 with a total gas flow rate of 1200 ml min−1. The effects of regeneration temperature and ramping rate on sorbent regeneration performance were demonstrated. The maximum sorbent regeneration efficiency of 97.2% was achieved under the regeneration condition of 110 °C and 5 °C min−1. CO2 sorption capacity of the amine-tethered sorbent kept stable within 5 repeated cycles. These findings indicate that the amine-tethered sorbent could be a good candidate for on-site CO2 capture from flue gas in co-firing power plants.

Coupling of bromide and on-line mechanical modified fly ash for mercury removal at a 1000 MW coal-fired power plant

Modified fly ash is a potential competitive sorbent for flue gas mercury remove in coal-fired power plant. The adsorption characteristics of coal fly ash under different temperature and modification methods were studied. On-line modified fly ash as a sorbent for mercury removal at a coal-fired power plant was carried out. The results of laboratory show that the adsorption performance of a coupled bromide and mechanical modified fly ash was better than that of inherent fly ash and mechanical modified fly ash. Furthermore, it was found that high temperatures are more favorable for mercury adsorption. In a demonstration at a full-scale 1000 MW coal-fired power plant unit, injection of the bromide and mechanical modified fly ash resulted in a decrease of the total concentration of mercury emissions at the stack. Additionally, a decrease in Hg2+ from the SCR to the ESP was found. When injected modified fly ash, the final emission concentration of mercury at the unit outlet reached 1.15 μg/m3, with a mercury emission reduction efficiency of 56.1%.

Sorptive removal of toluene and m-xylene by municipal solid waste biochar: Simultaneous municipal solid waste management and remediation of volatile organic compounds

The remediation of volatile organic compounds (VOCs) from aqueous solution using Municipal solid waste biochar (MSW-BC) has been evaluated. Municipal solid waste was pyrolyzed in an onsite pyrolyzer around 450 °C with a holding time of 30 min for the production of biochar (BC). Physiochemical properties of BC were assessed based on X-Ray Fluorescence (XRF) and Fourier transform infra-red (FTIR) analysis. Adsorption capacities for the VOCs (m-xylene and toluene) were examined by batch sorption experiments. Analysis indicated high loading of m-xylene and toluene in landfill leachates from different dump sites. The FTIR analysis corroborates with the Boehm titration data whereas XRF data demonstrated negligible amounts of trace metals in MSW-BC to be a potential sorbent. Adsorption isotherm exhibited properties of both Langmuir and Freundlich which is indicative of a non-ideal monolayer adsorption process taking place. Langmuir adsorption capacities were high as 850 and 550 μg/g for toluene and m-xylene respectively. The conversion of MSW to a value added product provided a feasible means of solid waste management. The produced MSW-BC was an economical adsorbent which demonstrated a strong ability for removing VOCs. Hence, MSW-BC can be used as a landfill cover or a permeable reactive barrier material to treat MSW leachate. Thus, the conversion of MSW to BC becomes an environmentally friendly and economical means of solid waste remediation.

Clay-salt slimes of the \u201cBelaruskali\u201d - novel sorbents for management of liquid radioactive wastes and decontamination of environmental water streams

Clay-salt slimes, production wastes from “Belaruskali” (A Belarusian factory, producing potash fertilizers), have been tested as a low-cost, eco-friendly potential sorbent for the removal of radionuclides from aqueous solutions, and may be a component of the cement filling of drums used in the storage of radioactive wastes. The efficiency of sorptive removal of caesium(I)-137, strontium(II)-90, europium(III)-152, and americium(III)-241 was examined with respect to the time of phase equilibration, pH, sorbent dosage, and the presence of salts and complexing agents. Irradiation stability of the material was also studied. It was found that uptake of the radionuclides is almost complete. A procedure for the removal of technetium-99 has been also proposed. Experimental results obtained within the presented work confirm our expectations.

Molecular modeling and experimental study of a new peptide-based microextraction fiber for preconcentrating morphine in urine samples.

Antimicrobial peptides (AMPs) are best known for their bactericidal properties; however, due to their unique and flexible structures, they have also been proposed as potential selective sorbents for specific molecules. In the present study, we aimed to design and produce a new peptide-based microextraction fiber for preconcentrating morphine in urine samples. The binding of morphine to the peptide was first evaluated by computational simulation using the Molecular Operating Environment (MOE) 2015.10 software. A similar study was then performed using DS BIOVIA Materials Studio 2017 v17.1.0.48, which confirmed the results of the simulation carried out with MOE. Afterwards, those results were also confirmed by experimental research. In the experimental evaluation, carbon nanotubes (CNTs) were initially carboxylated with H2SO4/HNO3 (3:1) and then functionalized with the peptide. FTIR analysis, Raman measurements, and SEM imaging were used to confirm that CNT functionalization was successful as well as to check the nanostructure of the fiber. To evaluate the functionality of the fiber, it was inserted into a microtube containing a urine sample that included morphine and then sonicated for 5min at 40°C. Afterwards, the fiber was washed with methanol 20% (H2O/methanol) and the resulting sample was analyzed by HPLC. This procedure was repeated for different concentrations of morphine in the urine sample. The computational and experimental results showed that a morphine concentration as low as 0.25ppb in urine could be adsorbed and detected using the peptide fiber. Therefore, given its semi-selective binding affinity for morphine, this peptide-based fiber can be considered a new approach to the detection of small amounts of morphine in biological samples.

Methane and Natural Gases Kinetic and Equilibrium Adsorption Comparison on Synthesised Porous Coconut Shell Kernel Activated Carbon

Instability of diesel and gasoline market price with the generation of environmental pollution attracted world attention in looking towards natural gas (NG) as a means of alternative fuel. This research work presents an investigation of experimental adsorption uptake of pure methane (CH4) and NG onto a hybrid of coconut shell and polyetheretherketone (PEEK) porous carbon. The hybrid porous carbon was prepared by KOH microwave-assisted activation of a coconut shell with PEEK. The Porous carbon (M33P15) was used as a potential sorbent to investigate the adsorption characteristics of the two gasses. The adsorption is applied at an ambient and 5 °C adsorption temperatures and at a pressure of 3.5 MPa. The comparison is based on measuring adsorption uptake differences between the two gases onto porous carbon. The ideal CH4 and NG adsorption uptake on porous carbon are investigated using volumetric adsorption method. The CH4 adsorption capacity of 9.7045 and 9.9958 mmol CH4 adsorbed/g adsorbent was achieved at an ambient and 5 °C adsorption temperature. While NG adsorption capacity of 9.9432 and 10.0901 mmol NG adsorbed/g was achieved at an ambient and 5 °C adsorption temperatures. In conclusion, the results show that NG adsorption uptake is slightly higher than CH4 adsorption uptake. This is due to the ability of the adsorbent to adsorb other components of the NG other than CH4. It is also suggested that applying heat management strategies, by lowering the temperature of adsorbent during the adsorption process, can significantly improve the storage capacity of CH4 and NG.

An eco-friendly cellulose acetate chemical sorbent for hazardous volatile organic liquid spill: a perfect material to solve the issue of evaporating hazards

Accidents related to spilling of chemicals and chemical wastes are never ceasing, especially as our reliance on chemical products increases continuously. For the sake of workers’ safety and maintenance of our environment, it is important to not only reduce the frequency of such accidents but also minimize the damage from each accident through proper spill control methods. Our focus here is to address the issues regarding rapid evaporation of the hazardous volatile organic liquids spills and propose a potential sorbent material, cellulose acetate, which can significantly reduce the rate of evaporation of highly volatile chemicals such as acetone, acrolein, and propylene oxide. Compared to conventional chemical sorbents such as activated carbon, expanded vermiculite, and cellulose, cellulose acetate not only exhibits higher vapor retention abilities, but also demonstrates comparable sorption efficiencies for sorption of acetone, acrolein, and propylene oxide. Cellulose acetate is also an environmentally friendly and economical material that is safe to use even for sorption of highly flammable chemicals, thus, its potential as a new class of commercial chemical sorbent is very promising.

Mechanochemically Synthesised Coal-Based Magnetic Carbon Composites for Removing As(V) and Cd(II) from Aqueous Solutions.

The continued decrease in water quality requires new advances in the treatment of wastewater, including the preparation of novel, effective, environmentally friendly, and affordable sorbents of toxic pollutants. We introduce a simple non-conventional mechanochemical synthesis of magnetically responsive materials. Magnetic lignite and magnetic char were prepared by high-energy ball co-milling from either raw Slovak lignite or coal-based char together with a ferrofluid. The products were characterised by X-ray diffraction, electron microscopy, 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), volumetric magnetic susceptibility, and low-temperature nitrogen adsorption, and both magnetic carbons were comparatively tested as potential sorbents of As(V) oxyanions and Cd(II) cations in aqueous solutions. The magnetic char was an excellent sorbent of As(V) oxyanions (Qm = 19.9 mg/g at pH 3.9), whereas the magnetic lignite was less effective. The different sorption properties towards arsenic anions may have been due to different oxidation states of iron on the surfaces of the two magnetic composites (determined by XPS), although the overall state of iron monitored by Mössbauer spectroscopy was similar for both samples. Both magnetic composites were effective sorbents for removing Cd(II) cations (Qm (magnetic lignite) = 70.4 mg/g at pH 6.5; Qm (magnetic char) = 58.8 mg/g at pH 6.8).

Enhanced Capacities of Mixed Fatty Acid-Modified Sawdust Aggregators for Remediation of Crude Oil Spill.

Mixed fatty acid-modified aggregators have been developed as potential crude oil sorbents. Cheap pine wood flour was first modified with oleic acid (OA) and further modified with a second fatty acid by a leaving group chemistry, where a surface hydroxyl group is first replaced by p-toluenesulfonyl group and a fatty acid forms a covalent bond on sawdust surface through esterification at the elevated temperature (55 °C). Two OA-modified base materials, pine/OA-106 and pine/OA-124, with different OA-coverages were first prepared and the second fatty acids with C3, C6, C8, C10, C12, C14, or C16 alkyl chains were applied to cover the remaining surface hydroxyl groups. The crude oil sorption capacities of the mixed fatty acid-modified aggregators were studied and compared with those of the base materials. The results showed that mixed fatty acid-modified aggregators increased up to 45.6% more crude oil sorption than those of OA-modified base materials. A correlation between surface property and sorption capacity was studied by moisture sorption, Fourier transform infrared spectroscopy, X-ray diffraction, 13C cross polarization and magic angle spinning nuclear magnetic resonance, thermal gravimetric analysis, and scanning electron microscopy. To our knowledge, no report has been published for mixed fatty acid-modified herders or aggregators in the environmental remediation.

Inorganic carbonate composites as potential high temperature CO2 sorbents with enhanced cycle stability.

A calcium magnesium carbonate composite (CMC) material containing highly porous amorphous calcium carbonate (HPACC) and mesoporous magnesium carbonate (MMC) was synthesized. CMCs with varying HPACC : MMC mol ratios and high BET surface area (over 490 m2 g−1) were produced. The CMCs retained the morphology shared by HPACC and MMC. All these materials were built up of aggregated nanometer-sized particles. We tested the CO2 uptake properties of the synthesized materials. The CMCs were calcined at 850 °C to obtain the corresponding calcium magnesium oxide composites (CMOs) that contained CaO : MgO at different mol ratios. CMO with CaO : MgO = 3 : 1 (CMO-3) showed comparable CO2 uptake at 650 °C (0.586 g g−1) to CaO sorbents obtained from pure HPACC (0.658 g g−1) and the commercial CaCO3 (0.562 g g−1). Over 23 adsorption–desorption cycles CMOs also showed a lower CO2 uptake capacity loss (35.7%) than CaO from HPACC (51.3%) and commercial CaCO3 (79.7%). Al was introduced to CMO by the addition of Al(NO3)3 in the synthesis of CMC-3 to give ACMO after calcination. The presence of ∼19 mol% of Al(NO3)3 in ACMO-4 significantly enhanced its stability over 23 cycles (capacity loss of 5.2%) when compared with CMO-3 (calcined CMC-3) without adversely affecting the CO2 uptake. After 100 cycles, ACMO-4 still had a CO2 uptake of 0.219 g g−1. Scanning electron microscope images clearly showed that the presence of Mg and Al in CMO hindered the sintering of CaCO3 at high temperatures and therefore, enhanced the cycle stability of the CMO sorbents. We tested the CO2 uptake properties of CMO and ACMO only under ideal laboratory testing environment, but our results indicated that these materials can be further optimized as good CO2 sorbents for various applications.

Preconcentration of tropane alkaloids by a metal organic framework (MOF)-immobilized ionic liquid with the same nucleus for their quantitation in Huashanshen tablets.

The application of ionic liquids (ILs) for the separation of bioactive compounds from various sample matrices is a burgeoning area. Here, a class of porous materials called metal-organic frameworks (MOFs) were combined with tropine-based ILs having structural similarity with natural tropane alkaloids for the quantitative analysis of Huashansheng tablets. Three MOFs (MIL-101, HKUST-1 and ZIF-8) were used to form the composite with the a tropine-based IL (N-propyl-substituted tropine hexafluorophosphate, [C3tr][PF6]), using the ship-in-a-bottle (SIB) synthesis approach. The performance of the hybrid IL/MOF composite (IL@MOF) was evaluated as a potential sorbent for application in the dispersive solid-phase-extraction-based enrichment of tropane alkaloids, followed by chromatographic analysis. It was found that [C3tr][PF6]@MIL-101 exhibited excellent adsorption capacity, and the extraction results showed satisfactory recoveries in the range of 91.5-104.7% (RSD < 5%). Further, the limit of detection went down to 10-20 μg L-1 with a linear range from 100-500 μg L-1, which proved that an adsorbent with the same nucleus as the target objects would be more suitable and efficient for their later extraction.

Zeolites and zeolite-based materials in extraction and microextraction techniques.

Zeolites are ordered crystalline materials with a promising performance for a wide range of applications such as catalysis, petrochemistry, environmental remediation, and medicine, but have scarcely been evaluated in Analytical Chemistry. Their unique and fascinating properties such as their high surface area, high adsorption capacity and molecular selectivity, chemical and thermal stability, ion-exchange capacity, low cost extraction and synthesis, and their easy modification, which provides a wide range of zeolite-based materials, make zeolites potential sorbents for extraction procedures. Therefore, in this review, we provide an overview of the current status of zeolites and zeolite-based materials used in extraction and microextraction techniques with reference to recent applications and highlight some of the novel advances.

Separation of CH4/N2 of Low Concentrations From Coal Bed Gas by Sodium-Modified Clinoptilolite.

Clinoptilolite is a widely distributed tectosilicate, mainly composed of Al2O3, SiO2 with exchangeable cations such as Ca, K, Mg, and Na. In this research, raw clinoptilolite was ground, gravimetrically concentrated and ion-exchanged using different concentrations of NaCl solution. Then the modified clinoptilolite powder was formulated into particles as adsorbents. The adsorbents were applied to CH4 separation in coal bed gas. The raw and modified clinoptilolites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), atomic emission spectrometer (ICP-AES), Fourier transform infrared spectrometer (FTIR), and Brunauer Emmett Teller (BET) specific surface area. The CH4 absorptivity by raw and modified clinoptilolites was evaluated using pressure swing adsorption (PSA) to assess the CH4 separation ability. The results indicated that the ion-exchanged clinoptilolite using 0.2 mol/L NaCl solution was found to be promising for the kinetic PSA separation of CH4/N2, giving a better absorptivity for CH4 separation under different influence factors. Based on the simulated static experiments, it was indicated that both CH4 and N2 were capable of diffusing into clinoptilolite while N2 adsorption by clinoptilolite was excellent. The experiment results also indicated that ion-exchanged clinoptilolite using a 0.2 mol/L NaCl solution was the optimal adsorbent for separating CH4/N2 at the low pressure condition. From the simulated dynamic experiments, the ion-exchanged clinoptilolite using a 0.2 mol/L NaCl solution as a potential sorbent in kinetic PSA processes for N2/CH4 separation, exhibited the best performance at 648 K under 0.2 MPa within 28 min, in comparison to the raw clinoptilolite and clinoptilolite under other modification conditions. In the next phase of research, the modified clinoptilolite will be tested for CH4 separation in real coal bed gas.

Amine-Functionalized Metal-Organic Frameworks and Covalent Organic Polymers as Potential Sorbents for Removal of Formaldehyde in Aqueous Phase: Experimental Versus Theoretical Study.

Porous materials have been identified as efficient sorbent media to remove volatile organic compounds. To evaluate their potential as adsorbents, the adsorptive removal of formaldehyde (FA) in aqueous environments was investigated using four materials, two water-stable metal-organic frameworks (MOFs) of UiO-66 (U6) and U6-NH2 (U6N) and two covalent organic polymers (COPs) with amine-functionality, CBAP-1-EDA (CE) and CBAP-1-DETA (CD). U6N exhibited the highest removal capacity of 93% (0.56 mg g-1) of the tested materials [e.g., CE (81.1%, 0.53 mg g-1) > CD (67.2%, 0.43 mg g-1) > U6 (66.9%, 0.42 mg g-1)], which was 2 times higher than that of the reference sorbent, activated carbon (AC: 50%, 0.30 mg g-1). The results of Fourier transform infrared and powder X-ray diffraction analyses confirmed the interactions between FA molecules and the amine components of the materials (U6N, CD, and CE). According to density functional theory calculations, the formation of hydrogen bonds between FA molecules and amine components was apparent and was further verified by FA/amine distance (CD: 2.83, CE: 2.88, and U6N: 2.66 Å) along with enthalpy values (CD: -32.4, CE: -45.5, and U6N: -272 kJ mol-1). In case of U6, the major interactions occurred in the metal-clusters (-19.3 kJ mol-1) via electrostatic interactions (distance: 5.49 Å). Furthermore, the sorption by amine-functionalized materials such as U6N is suggested to be dominated by hydrogen bonding which ultimately led to the formation of imine. If the performance of the tested materials is evaluated in terms of partition coefficient, U6N (1153 mg g-1 mM-1) is found as the outperformer in all tested subjects. Regeneration of spent MOFs/COPs was also plausible in the presence of ethanol to maintain their structural integrity even after 10 adsorption-desorption cycles. Overall, the selected MOFs/COPs were seen to have very high removal capacity for hazardous FA molecules in aqueous phase.

Water compatible functionalized chitosan-based 4-HBA mimic imprinted polymer as a potential sorbent for salicylic acid

ABSTRACT An efficient acrylamide grafted chitosan (AGCTS)-based polymer (AGCTS-based mimic 4-hydroxy benzoic acid imprinted polymer [AGMIP]) was synthesized using 4-hydroxy benzoic acid as a mimic template for the recognition of salicylic acid (SA) in aqueous solution. The influence of grafting parameters on grafting percentage of AGCTS was studied. AGMIP was characterized by scanning electron microscopy, Fourier transform infrared spectrometer, and Brunauer–Emmett–Teller surface area analysis. Adsorption process could be well described by Langmuir and Temkin adsorption isotherm model and the maximum adsorption capacity calculated for SA was 62 mg/g. The adsorption kinetic data was fitted with pseudo-second order equation. The experimental results suggest that AGMIP is a promising adsorbent for SA. Abbreviations AGMIP: Acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer; SA: salicylic acid; 4-HBA: 4-hydroxy benzoic acid; GA: gallic acid; 2,5-DBA: 2,5-dihydroxy benzoic acid; 4-HBACTSMIP: chitosan-based 4-hydroxy benzoic acid molecularly imprinted polymer; SACTSMIP: chitosan-based salicylic acid molecularly imprinted polymer; AGCTS: acrylamide grafted chitosan; AGMIPAE: acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer after extraction; AGMIPBE: acrylamide grafted chitosan-based mimic 4-hydroxy benzoic acid imprinted polymer before extraction; COD: Chemical oxygen demand; PCA: Protocatechuic acid; APS: Ammonium persulphate.

Sorption of cadmium by rice husk char, bamboo char, and coconut shell char in aqueous solutions

Cadmium (Cd) is a byproduct of zinc production. It has a high solubility, mobility and biological accumulation leading to a risk of bone and kidney damage after long-term exposure. Sorption is an effective method to treat Cd-contaminated water. As a great potential contaminant sorbent, biochar can be produced from rice husk, coconut shell and bamboo under their respective optimum conditions for the sorption of toxic metal ions were used as representatives. Sorption models of kinetics and isotherms were used to fit the experimental results. Pseudo-first-order models fitted the data better than pseudo-second-order for all types of biochar. The Cd2+ sorption capacity of coconut shell char and bamboo char was higher than rice husk char (7.3723 mg/g ≈ 7.3835 mg/g > 5.0345 mg/g). Freundlich model fitted the results of coconut shell biochar and bamboo biochar better than Langmuir model, which indicate a strong bond for Cd2+ sorption. In contrast, for rice husk biochar Langmuir model fitted the results better than Freundlich model indicating monolayer sorption mechanism dominated the sorption.