Chemisorption Mechanism Research Articles

Green surface functionalization of chitosan with spent tea waste extract for the development of an efficient adsorbent for aspirin removal.

This study investigates the feasibility of spent tea waste extract (STWE) as a green modifying agent for the modification of chitosan adsorbent towards aspirin removal. Response surface methodology based on Box-Behnken design was employed to find the optimal synthesis parameters (chitosan dosage, spent tea waste concentration, and impregnation time) for aspirin removal. The results revealed that the optimum conditions for preparing chitotea with 84.65% aspirin removal were 2.89g of chitosan, 18.95mg/mL of STWE, and 20.72h of impregnation time. The surface chemistry and characteristics of chitosan were successfully altered and improved by STWE, as evidenced by FESEM, EDX, BET, and FTIR analysis. The adsorption data were best fitted to pseudo 2nd order, followed by chemisorption mechanisms. The maximum adsorption capacity of chitotea was 157.24mg/g, as fitted by Langmuir, which is impressive for a green adsorbent with a simple synthesis method. Thermodynamic studies demonstrated the endothermic nature of aspirin adsorption onto chitotea.

Synthesis and Characterization of Mesoporous Silica Modified with Purpald and Its Application in the Preconcentration of Cu2+ and Cd2+ from Aqueous Samples through Solid-Phase Extraction

The synthesis of an organofunctionalized mesoporous silica was accomplished by a two-step process involving (1) the co-condensation of a silylant agent at the surface of silica, followed by (2) the immobilization of Purpald (ligand) at the organic termination of the silytant agent. The characterization of the organofunctionalized material indicated the presence of NH2 groups, and the immobilization of the ligand was confirmed by 29Si- and 13C-nuclear magnetic resonance. The material’s surface area was determined as 370 m2 g−1. Batch adsorption experiments enabled the determination of optimum pH conditions for the adsorption of Cu(II) and Cd(II). Under optimal pH, the pseudo-second-order kinetic model and Langmuir model provided the best correlations to describe the materials adsorption behavior, suggesting a chemisorption mechanism. When tested in continuous-flow preconcentration experiments, the flow rate and eluent concentration demonstrated to affect the removal of Cu(II) and Cd(II), while the buffer concentration had an effect only over the adsorption of Cu(II). Under optimized preconcentration conditions, it was possible both to determine the concentrations of Cu(II) and Cd(II) in samples such as mineral water, ground water, tap water and river water. Ions commonly found in drinking and natural waters (Na+, K+, Ca2+, Mg2+, Fe3+, Ba2+, Cl−, SO42−, HCO3−, and H2PO4−) did not affect the preconcentration of any of the studied analytes. Reutilization experiments indicated that the adsorbent material can withstand at least 40 adsorption/desorption preconcentration cycles with no efficiency loss.

Aminosilane-Modified Ordered Hierarchical Nanostructured Silica for Highly-Selective Carbon Dioxide Capture at Low Pressure

Ordered hierarchical nanostructured silica (OHNS) adsorbents were prepared, and their surface was controllably modified by aminosilanization using two different aminosilanes, one bearing one primary amine unit per molecule (4-aminobutyltriethoxysilane, ABTS) and the other bearing both a primary and a secondary amine (N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, AAMS). Following physicochemical, structural, morphological, and porosity characterization, the CO2 adsorption performance was evaluated at low pressures (up to 100 mbar) and at different temperatures (25, 45, and 60 °C), including determination of CO2 adsorption–desorption, kinetics, CO2/N2 selectivity, regeneration/cycling, heat of adsorption, and CO2 adsorption under humid conditions. The unique hierarchical silica framework together with the aminosilanization scheme applied resulted in enhanced kinetics and CO2 uptake, the latter being increased with temperature, thus revealing a dominant chemisorption mechanism, which was further evidenced by the increase in the enthalpy of adsorption of the modified materials compared to the pristine OHNS. Among the tested adsorbents, at 100 mbar and 25 °C, the OHNS modified by AAMS yielded the highest CO2 uptake under dry (1.3 mmol/g) and wet (1.9 mmol/g) conditions. Notably, at very low pressure (1 mbar), the CO2 capacity of OHNS-AAMS reached >40% of the material’s total uptake at 1 bar. Compared to the unmodified OHNS, the CO2 capacity of the OHNS-AAMS and OHNS-ABTS increased by approximately 21- and 16-fold, respectively, at 1 mbar and 25 °C. At even lower pressure (0.4 mbar), a capacity of 0.55 mmol/g was evidenced for OHNS-AAMS in dry CO2. A very high CO2/N2 selectivity of the AAMS-modified analogue at low pressure was also obtained, i.e., 13,854 at 50 mbar, confirming the significant increase in CO2-philicity via aminosilanization with aminosilanes bearing combined primary and secondary amine groups. Furthermore, the water affinity of the aminosilane-modified OHNS adsorbents was found to decrease, which is beneficial for capture from humid mixtures. Cyclic stability was confirmed by performing 10 thermal pressure swing adsorption (TPSA) cycles up to 100 mbar. The hierarchical nanostructured silica-based framework and the functionalization scheme presented here render these robust systems promising for selective CO2 capture at low pressures in industrial applications and direct air capture.

Synthesis of bioinspired sorbent and their exploitation for methylene blue remediation

In this research article, novel starch phosphate grafted polyvinyl imidazole (StP-g-PIMDZs) was synthesized. Firstly, a phosphate group was attached to starch polymer via a phosphorylation reaction. Next, 1-vinyl imidazole (VIMDZ) was grafted on the backbone of starch phosphate (StP) through a free radical polymerization reaction. The synthesis of these modified starches was confirmed by 1H NMR, 31P NMR and FT-IR techniques. The grafting of vinyl imidazole onto StP diminished the crystallinity. Due to the insertion of the aromatic imidazole ring, the StP-g-PIMDZs demonstrated greater thermal stability. The StP and StP-g-PIMDZs were used as sorbents for the adsorption of methylene blue dye (MBD) from the model solution. The maximum removal percentage for starch, StP, StP-g-PIMDZ 1, StP-g-PIMDZ 2 and StP-g-PIMDZ 3 was found to be 60.6%, 66.7%, 74.2%, 85.3 and 95.4%, respectively. The Pseudo second order kinetic model and Langmuir adsorption isotherm were best suited to the experimental data with R2 = 0.999 and 0.99, respectively. Additionally, the thermodynamic parameters showed that the adsorption process was feasible, spontaneous, endothermic and favored chemi-sorption mechanism.

Acetylated corn and potato starches as an alternative to the toxic inorganic coagulants/flocculants for wastewater treatment

Inorganic coagulants/flocculants have been key in water treatments. However, last years, it has been reported the potential contamination that these give to the environment and serious risks to human health. For that reason, new eco-friendly alternatives have been the subject of exploration and research. This work focused on developing and elaborating a natural flocculant based on corn and potato starches, and its application in industrial wastewater treatments. Starches were isolated from corn and potato, and modified by acetylation method with the aim of improve its solubility. The morphological characterization using SEM identified the effects of acetylation process, the surface of acetylated corn and potato starches presented small erosions. The vibrational characterization via FTIR elucidated the physicochemical changes owing to acetylation. It found the replace of hydroxyl groups of α-glucose by the acetyl ones of amide I. A loss of the crystalline quality of corn starch were identified through structural characterization utilizing DRX. The partial replacement of hydroxyl by acetyl groups due to acetylation induced structural modifications corroborated employing the area under curve of the diffraction patterns. In the case of potato starch, its characteristic hexagonal crystalline structure was favored by the acetylation process, as it exhibited a more defined diffraction pattern. The thermal analysis by means of TGA found three thermal events for the acetylated potato starch and four for the acetylated corn starch. The fourth thermal event in the acetylated potato starch was associated with the ester presence of the added group. The thermal degradation occurred at lower temperatures as mass loss curves showed that acetylation weakened the polymer chains. The pH of zero point charge was 6.52 for the acetylated corn starch and 5.55 for the acetylated potato one, indicating that anionic contaminants be retained at a pH below 6.52 and 5.55 for each case, and the removal of cationic contaminants will favor at pH above these values. The efficiency determination of the modified starch-based flocculant was performed utilizing a jar test at different concentrations to find the optimal concentration of the coagulant/flocculant. Turbidity, color, pH, and electrical conductivity measurements were made before and after the water treatment. These results indicated that both corn and potato starches showed good performance as coagulants/flocculant. The kinetics for adsorption was study using the pseudo-first and pseudo-second order kinetic models, the intra-particle diffusion model, and the Elovich kinetic one. These analyzes identified that the absorption process is governed by chemisorption mechanisms since the pseudo-second order kinetic model was the most accurate for describing the absorption kinetic of both acetylated corn and potato starches according to the R2, SSE, MSE, and RMSE.

NZVI-Based Nanomaterials Used for Phosphate Removal from Aquatic Systems.

In the last decade, the application of nanoscale zero-valent iron (nZVI) has garnered great attention as an adsorbent due to its low cost, non-toxicity, high porosity, and BET-specific surface area. In particular, the immobilization of nZVI particles onto inorganic and organic substrates (nanocomposites) decreased its agglomeration, allowing them to be effective and achieve greater adsorption of pollutants than pristine nanoparticles (NPs). Although nZVI began to be used around 2004 to remove pollutants, there are no comprehensive review studies about phosphate removal from aquatic systems to date. For this reason, this study will show different types of nZVI, pristine nZVI, and its nanocomposites, that exist on the market, how factors such as pH solution, oxygen, temperature, doses of adsorbent, initial phosphate concentration, and interferents affect phosphate adsorption capacity, and mechanisms involved in phosphate removal. We determined that nanocomposites did not always have higher phosphate adsorption than pristine nZVI particles. Moreover, phosphate can be removed by nZVI-based nanoadsorbents through electrostatic attraction, ion exchange, chemisorption, reduction, complexation, hydrogen bonding, and precipitation mechanisms. Using the partition coefficient (PC) values, we found that sepiolite-nZVI is the most effective nanoadsorbent that exists to remove phosphate from aqueous systems. We suggest future studies need to quantify the PC values for nZVI-based nanoadsorbents as well as ought to investigate their phosphate removal efficiency under natural environmental conditions.

Outstanding anti-corrosion performance of two pyrazole derivatives on carbon steel in acidic medium: Experimental and quantum-chemical examinations

Corrosion inhibition performance of two pyrazole derivatives, namely N-((1H-pyrazol-1-yl)methyl)pyrimidin-2-amine (PPA), 2-(((1H-pyrazol-1-yl)methyl)amino)benzoic acid (PMB), carbon steel (CS) was assessed in 1 M HCl medium by means of electrochemical impedance spectroscopy (EIS), weight loss, potentiodynamic polarization measurements (PDP), Uv–visible spectroscopy, and scanning electron microscopy with energy dispersive X-ray (SEM- EDX), as well as molecular modeling techniques. Results indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature to reach a maximum of 94 % for PPA and 92 % for PMB at 10−3 M and 303 K, respectively, whereas it was 76.9 and 72.3 %, respectively, at 10−3M and 333 K. PDP plots reveal the anodic-type behavior of PPA while the mixed-type behavior of PMB. The EIS plots showed that charge transfer resistance increased and double-layer capacitance decreased with increasing the concentration of studied inhibitors due to the adsorption of inhibitor molecules on the CS surface. Moreover, the adsorption of pyrazole derivatives on the CS surface obeys the Langmuir adsorption isotherm and contains a chemisorption mechanism. Thermodynamic parameter magnitudes suggest that pyrazole derivatives were physiosorbed on the CS surface. SEM-EDX revealed the formation of an adsorption-related protective inhibitor film on the CS surface. Theoretical studies using density functional theory (DFT) for PPA and PMB molecules are performed in gas and aqueous phase conditions. The calculated data are in good agreement with the experimental results. Molecular Dynamic simulations (MDS) exhibit that the neutral and protonated forms of PPA and PMB adsorb on Fe (110) surface with a parallel mode.

Experimental and theoretical studies on the corrosion inhibition on the surface of C-steel in hydrochloric acid solutions using N1, N1'-(ethane-1,2-diyl)bis(N2-(4-(di-methylamino)benzylidene)ethane-1,2-diamine)

The inhibition effect of N1,N1'-(ethane-1,2-diyl)bis(N2-(4-dimethyl-amino)benzylidene)-ethane-1,2-diamine), (EDDB) on the corrosion of C-steel in 1.0 M HCl solution was investigated using gasometry, gravimetry, potentiodynamic polarization, and electrochemical impedance spectroscopy. The impact of temperature and inhibitor concentration were explored to illustrate the mechanism of inhibition. The data showed that EDDB is a good inhibitor for the corrosion of C-steel in 1.0 M HCl solution. The inhibition is based on adsorption phenomena, which correlates to the Langmuir adsorption model. The inhibition efficiency increase with the EDDB concentration to reach a maximum value of 95.2% at 0.005 M and 25 °C. Potentiodynamic polarization data confirmed that the EDDB behaves as a mixed-type inhibitor. The negative values of ΔGoads confirm the stability of the formed film on the C-steel with a spontaneous process and take values between – 35.34 and - 39 kJ/mol depending on the temperature which confirms the physical- and chemisorption mechanism. The SEM/EDS data disclosed that the carbon steel was protected by the EDDB inhibitor. DFT computations and MC simulation were achieved on the EDDB Schiff-base inhibitor to correlate with experimental data. The results obtained from the different methods are in good agreement.

Controlled alkali etching of MOFs with secondary building units for low-concentration CO2 capture.

Low-concentration CO2 capture is particularly challenging because it requires highly selective adsorbents that can effectively capture CO2 from gas mixtures containing other components such as nitrogen and water vapor. In this study, we have successfully developed a series of controlled alkali-etched MOF-808-X (where X ranges from 0.04 to 0.10), the FT-IR and XPS characterizations revealed the presence of hydroxyl groups (-OH) on the zirconium clusters. Low-concentration CO2 capture experiments demonstrated improved CO2 capture performance of the MOF-808-X series compared to the pristine MOF-808 under dry conditions (400 ppm CO2). Among them, MOF-808-0.07 with abundant Zr-OH sites showed the highest CO2 capture capacity of 0.21 mmol g-1 under dry conditions, which is 70 times higher than that of pristine MOF-808. Additionally, MOF-808-0.07 exhibited fast adsorption kinetics, stable CO2 capture under humid air conditions (with a relative humidity of 30%), and stable regeneration even after 50 cycles of adsorption and desorption. In situ DRIFTS and 13C CP-MAS ssNMR characterizations revealed that the enhanced low-concentration CO2 capture is attributed to the formation of a stable six-membered ring structure through the interaction of intramolecular hydrogen bonds between neighboring Zr-OH sites via a chemisorption mechanism.

Mesoporous, phase-pure Al3+ engrafted spinel ZnAlxB2−xO4 x = 0, 1; B = Cr3+/Fe3+) for effective fluoride chemisorption and photodegradation of azo/non-azo dyes

Well-crystalline, cubic, spinel-type, mesoporous ZnAlxB2−xO4 [x = 0, 1; B= Cr3+ (abbreviated as ZAC0, ZAC1) and B = Fe3+ (abbreviated as ZAF0, ZAF1)] calcined at 700 °C for 3 h was synthesized by the solution-combustion method using urea and triethanolamine as precursors. The phase formation was confirmed by PXRD, TEM, and HRTEM analyses. The phase formation mechanism was established by simultaneously recorded TGA-FTIR hyphenation analyses. ZAC1 with SBET = 30.02 g/m2 and average pore size 5.67 nm, showed the highest ∼86.36 % of photodegradation efficiency for reactive black 5 and 98.00±2 % fluoride removal, and reusable up to 5th cycles at pH 7. The mechanisms of fluoride chemisorption and photodegradation were established by the surface-electrostatically-controlled-pH model. The chemisorption of fluoride was supported by XPS and FTIR analyses. The photodegradation followed the Pirkanniemi path as established by the HPLC, FTIR, and EPR studies, and Krӧger-Vink notation. Treatment of fluoride-containing field water sample analyses using ZAC1 was satisfactory.

Coral-like TiO2/organosilane hybrid particles with rapid adsorption of methyl orange

TiO2/Bis[3-(trimethoxysilyl)propyl]amine (BTMSPA) hybrid particles with a coral morphology were prepared using a facile method and used for the removal of methyl orange (MO) dye from wastewater. The structure of the TiO2/BTMSPA particles and the adsorption mechanism for MO were analyzed. Meanwhile, the adsorption isotherms and kinetics of MO on the particles were also studied. During the preparation of the TiO2/BTMSPA hybrid adsorbent, some of the BTMSPA linked the TiO2 particles to form a skeleton, while the remaining BTMSPA grew in situ on the TiO2 surface into nanopapillae, forming a micro/nano-porous coral-like structure. The secondary amine group in BTMSPA acted as an adsorbent via a single molecular layer chemisorption mechanism. In a neutral environment, the decolorization rate of MO was 83.3% after 1 min, eventually reaching 91.2 %. The maximum adsorption capacity was determined to be 90.3 and 369.3 mg/g under neutral and acidic conditions, respectively. Furthermore, the hybrid particles also showed excellent performance for the removal of other anionic dyes and such as methyl blue and amaranth red, with a 100 % decolorization rate. The adsorbent had good universality and excellent regeneration performance after an alkaline washing step.

Adsorption of cadmium vapor by calcium-based adsorbents in simulated flue gas: Experimental and density functional theory studies

Calcium-based adsorbents are considered as effective high-temperature adsorbents for the removal of heavy metal in the furnace. In this work, the adsorption characteristics and reaction mechanism of calcium-based adsorbents for cadmium vapor were investigated by adsorption experiments and density functional theory (DFT) methods. The adsorption experiments showed that the adsorption performance of CaO for cadmium vapor was significantly better than Ca(OH)2, Calcite and CaSO4. The adsorption capacity of CaO adsorbent for cadmium increased firstly and then decreased with the increase of temperature. The enhanced trapping capacity of CaO for cadmium vapor with increasing temperature was associated with enhanced chemisorption, while the decrease in trapping capacity at high temperature could be attributed to adsorbent sintering. In addition, the results of DFT calculations showed that CaO had good adsorption capacity for various Cd species, and the order of the adsorption capacity was: CdO > CdCl2 > CdCl > Cd. The chemisorption mechanism dominated the adsorption of Cd species on the CaO (001) surface, and the central O site was the reactive site and electron transfer channel for the adsorption of Cd. This work provided a reference for the application of heavy metal vapor capture technology based on calcium-based minerals.

Coupling of carboxymethyl starch with 2-carboxyethyl acrylate: A new sorbent for the wastewater remediation of methylene blue

Textile and printing industries play a vital role in the economy of any country. But the effluents of these industries, which contain toxic Methylene Blue (MB) dye when mixed with fresh water, make it unfit for human health and aquatic life. For the removal of MB, different adsorbents were used, but they were expensive, non-biodegradable or less effective. In this research, novel carboxymethyl starch grafted poly 2-carboxyethyl acrylate (CM-St-g-P2CEtA) was synthesized by reacting carboxymethyl starch with 2-carboxyethyl acrylate. The reaction followed a free radical polymerization mechanism. The structure and properties of CM-St-g-P2CEtA were investigated by advanced analytical techniques. The CM-St-g-P2CEtA was employed for the remediation of Methylene Blue (MB) dye from wastewater. The removal percentage (%R) of MB was checked under different parameters, like different pH levels, different initial concentrations of dye, different adsorbent doses, and different contact times. The results obtained during the experiment were subjected to different adsorption and kinetic models. In the kinetic investigation, the experimental results were best represented by the pseudo-second-order kinetic model due to its high R2 value of 0.999. Similarly, with a regression coefficient (R2) value of 0.947, the Langmuir adsorption isotherm was best represented by the experimental results. The Langmuir adsorption model showed that MB dye was adsorbed on the surface of CM-St-g-P2CEtA in a monolayer pattern. The pseudo 2nd order kinetic model suggested that the adsorption process favored chemisorption mechanism. The CM-St-g-P2CEtA showed maximum percentage removal efficiency (%R) of 99.3% for MB dye.

Green reduction of graphene oxide using Annona muricata leaves extract for adsorption of methylene blue

• Green synthesis of reduced graphene oxide (rGO) using plant extract. • High specific surface area of rGO obtained. • Facile biosynthesis of rGO with simple and low cost. • The rGO exhibited adsorptivity towards methylene blue. Reduced graphene oxide (rGO) was prepared via a green reduction method by using Annona muricata leaves extract as bioreductor. The preparation was conducted by studying the effect of time of reduction on physicochemical feature and adsorption capability of rGO towards methylene blue. A variety of spectroscopic and analytical techniques, consist of Fourier-Transform infra-red, X-ray diffraction, scanning transmission electron microscopy, and transmission electron microscope were employed to characterize the physical properties of adsorbent. It is found that by varied time of reduction (4, 12 and 24 h), the longer time of reduction, the higher reduction efficiency and specific surface area of rGO obtained, which linearly correlated with the increasing adsorption capability towards methylene blue. The adsorption obeys pseudo-second order kinetics and follow the Langmuir isotherm as representation of the chemisorption mechanism over homogeneous surface of adsorbent. The high adsorption capability of material reaches ∼99% at 30 min of adsorption, suggests that the bioreduction method in this work is a potential method for reduced graphene oxide synthesis.

Adsorption studies of methyl orange dye removal from aqueous solution using Anchote peel-based agricultural waste adsorbent

A low-cost locally available agricultural waste-based Anchote peel adsorbent was studied to remove the methyl orange (MO) dye from wastewater which was created at laboratory conditions. The adsorbent was characterized by Fourier infrared and x-ray powder diffraction spectroscopic techniques. The adsorption capacity of the proposed adsorbent was investigated using the batch adsorption method. The best performance was achieved after careful optimization of experimental parameters such as adsorbent dose (0.4 g), initial dye concentration (70 mg/L), contact time (140 min), pH of the solution (8.0), and temperature (40 °C), respectively. The removal of MO from water using anchote peel adsorbent achieved a removal efficiency of 94.47% following the pseudo-second-order kinetic model, Freundlich isotherm, and chemisorption mechanism, respectively. The adsorbent showed heterogeneous surfaces and the adsorption of MO was thermodynamically spontaneous. Furthermore, the present results reveal that Anchote peel adsorbent is promising in future for the removal of organic dyes and other contaminants like toxic heavy metals from water and wastewater.

Controlled design of Na–P1 zeolite/ porous carbon composites from coal gasification fine slag for high-performance adsorbent

Low-cost and concentrated industrial wastes have been recognized as a sustainable resource for preparation of new functional materials. Here, a new method was designed for the synthesis of porous composites containing high-purity Na–P1 zeolite and porous carbon from waste coal gasification fine slag (CGFS), which was treated first by acid leaching to controllably remove metal impurities and adjust Si/Al ratio, followed by NaOH fusion and hydrothermal treatment. By leaching with 1.0 mol/L HCl solution, the Si/Al ratio of the raw CGFS increased to 5.7, and the obtained CZ-1.0 consisted of high-purity Na–P1 zeolite with a typical cone-shaped flower cluster shape. The residue carbon in CGFS can be further activated to form porous carbon and graphite carbon layers interposed in the zeolite structure. The specific surface area and pore volume of CZ-1.0 reached 153.91 m2/g and 0.18 cm3/g, respectively. CZ-1.0 exhibited remarkable adsorption performance for methylene blue (MB) with the adsorption capacity reaching 137.5 mg/g for 100 mg/L MB solution. The adsorption process is mainly controlled by the chemisorption mechanism, and the adsorption of MB by CZ-1.0 may include ion exchange, hydrogen bond interaction, π-π bond interaction and van der Waals force. NaCl solution was successfully used as the desorption agent to regenerate the composite material, and the removal rate remained above 92% after five cycles. This work provides an effective strategy to synthesize a practically applicable adsorbent from the waste coal gasification fine slag for the purification of MB wastewater.

Novel hydrophilic straw biochar for the adsorption of neonicotinoids: kinetics, thermodynamics, influencing factors, and reuse performance.

Nitenpyram (NIT) is the most water-soluble neonicotinoid (NEO). It has been shown to pose a serious threat to human health and the environment but was always ignored due to its limited market share. There were few experts who studied NIT's transport behavior on biochar. In this study, two types of biochar were co-activated separately using zinc chloride combined with phosphoric acid and potassium hydroxide combined with acetic acid, marked as ZBC and KBC. Characterizations suggested that hydrophilic ZBC and KBC had more surface functional groups than unmodified biochar (BC), and specific surface areas of ZBC (456.406 m2·g-1) and KBC (750.588 m2·g-1) were significantly higher than of BC (67.181 m2·g-1). The pore structures of KBC and ZBC were hierarchical porous structures with different pore sizes and typical microporous structure, respectively. The adsorption performance of either NIT or IMI on KBC was better than that on ZBC. Only 0.4g·L-1 of KBC can absorb 89.62% of NIT in just 5min. The equilibrium adsorption amounts of NIT on ZBC and KBC were 17.995mg·g-1 and 82.910mg·g-1. Elovich and Langmuir models were used to evaluate the whole adsorption process, which was attributed to the chemisorption mechanism. In addition, removal rates of NIT were negatively correlated to NIT's initial concentration and positively correlated to the dose of biochar. pH had almost no effect on adsorption, but the presence of salt ions can inhibit the removal of NIT. Long-term stabilities of biochars were also acceptable. These findings will promote the development in the preparation of biochar fields and provide a positive reference value for NEO removal.

L-Cysteine and silver nitrate based metal sulfide and Zeolite-Y nano adsorbent for efficient removal of mercury (II) ion from wastewater

In this study, zeolite-Ag2S nanohybrid material was synthesized by a sonication process combined with a hydrothermal method. The structure and morphology of hybrid nanomaterial was studied using XRD, SEM, TEM, BET and XPS analysis. Such microscopy studies show the uniform distribution of Ag2S in the zeolite matrix. For the comparison study, structure and morphology of pure zeolite and Ag2S were examined. The influence of Ag2S on the adsorption property was explained by studying the mercury adsorption. The synthesized zeolite-Ag2S nanohybrid material was applied as adsorbent to remove Hg (II) ion from wastewater. The removal rates of the nanohybrid material were greater than that of the sole zeolite. The maximum adsorption capacities of zeolite and zeolite-Ag2S nanohybrid were recorded 206 and 390 mg/g at 30 °C. The adsorption capacities of zeolite-Ag2S nanohybrid increases with increasing the temperature. The results show higher adsorption capacity for 50 °C as compared with adsorption temperature at 30 °C due to the chemisorption mechanism of the adsorption. Overall, the simple synthesis, high-effectiveness, and stability in aqueous phase features enable the prepared nanohybrid material to become excellent candidates for wastewater remediation.

Application of Dithiocarbamate Chitosan Modified SBA-15 for Catalytic Reductive Removal of Vanadium(V)

We have successfully synthesized dithiocarbamate chitosan modified SBA-15 (CS2C@SBA) composites, with promise in vanadium (V(V)) elimination. Among the three composites using different mass ratios of dithiocarbamate chitosan to SBA-15, CS2C@SBA−3, which had the highest CS2 substitution, showed the best performance on V(V) removal of which the maximum adsorption capacity could achieve 218.00 mg/g at pH 3.0. The adsorption kinetics were best fitted with a pseudo−second order reaction model, suggesting a chemisorption mechanism. Meanwhile, the Langmuir model fitted better with the adsorption isotherm, revealing a monolayer adsorption behavior. Through FTIR and XPS analysis, the functional group −SH was identified as dominating reduction sites on this composite, which reduced 73.1% of V(V) into V(IV) and V(III). The functional group −NH− was the main adsorption site for vanadium species. This reaction followed a catalytic reduction coupled adsorption mechanism reducing most of V(V) into less toxic vanadium species. Furthermore, CS2C@SBA−3 showed great selectivity towards V(V) in the presence of various co−existing ions in synthetic wastewater and real water samples. Moreover, CS2C@SBA−3 could retain a removal efficiency over 90% after five adsorption−desorption cycles. Based on the aforementioned results, we can conclude that CS2C@SBA−3 has great potential to be applied in efficient remediation of vanadium water−pollution.

SnS2 Nanosheets as a Template for 2D SnO2 Sensitive Material: Nanostructure and Surface Composition Effects.

Two-dimensional nanosheets of semiconductor metal oxides are considered as promising for use in gas sensors, because of the combination of a large surface-area, high thermal stability and high sensitivity, due to the chemisorption mechanism of gas detection. In this work, 2D SnO2 nanosheets were synthesized via the oxidation of template SnS2 nanosheets obtained by surfactant-assisted one-pot solution synthesis. The 2D SnO2 was characterized using transmission and scanning electron microscopy (TEM, SEM), X-ray diffraction (XRD), low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and IR spectroscopy. The sensor characteristics were studied when detecting model gases CO and NH3 in dry (RH25 = 0%) and humid (RH25 = 30%) air. The combination of high specific-surface-area and increased surface acidity caused by the presence of residual sulfate anions provides a high 2D SnO2 sensor's signal towards NH3 at a low temperature of 200 °C in dry air, but at the same time causes an inversion of the sensor response when detecting NH3 in a humid atmosphere. To reveal the processes responsible for sensor-response inversion, the interaction of 2D SnO2 with ammonia was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in dry and humid air at temperatures corresponding to the maximum "positive" and maximum "negative" sensor response.