A New Rapid Determination Method of Soil Organic Carbon Adsorption Coefficients of Pesticides with Soil Column Liquid Chromatography

Soil column liquid chromatography (SCLC) was developed to determine soil organic carbon adsorption coefficients (E-oc) for chemicals. The uptake by soil of pesticides from water can be conveniently calculated from the related breakthrough curves (BTC). The nine pesticides chosen for determination in this study are soluble ones, with their water solubility ranging from 62 mg/L to Z mg/L. In comparing with existing methods of K-oc, SCLC possesses rapid, online and accurate characteristics.

Fluorescence spectroscopic studies of the effect of granular activated carbon adsorption on structural properties of dissolved organic matter fractions

This work investigated the effect of granular activated carbon adsorption （GACA） on fluorescence characteristics of dissolved organic matter （DOM） in secondary effluent, by means of excitation-emission matrix （EEM） spectra, the fluorescence regional integra- tion （FRI） method, synchronous spectra, the fluorescence index defined as the ratio of fluorescence emission intensity at wavelength 450nm to that at 500nm at excitation （λex）= 370 am, and the wavelength that corre- sponds to the position of the normalized emission band at its half intensity （λ0.5）. DOM in the secondary effluent from the North Wastewater Treatment Plant （Shenyang, China） was fractionated using XAD resins into 5 fractions： hydrophobic acid （HPO-A）, hydrophobic neutral （HPO- N）, transphilic acid （TPI-A）, transphi｜ic neutral （TPI-N） and hydrophilic fraction （HPI）. Results showed that fluorescent materials in HPO-N and TPI-N were less readily removed than those in the other fractions by GACA. The relative content of fluorescent materials in HPO-A, TPI-A and HPI decreased whereas that in HPO- N and TPI-N increased as a consequence of GACA. Polycyclic aromatics in all DOM fractions were preferen- tially absorbed by GACA, in comparison with bulk DOM expressed as DOC. On the other hand, the adsorption of aromatic amino acids and humic acid-like fluorophores exhibiting fluorescence peaks in synchronous spectra by GACA seemed to be dependent on the acid/neutralproperties of DOM fractions. All five fractions had decreased fluorescence indices as a result of GACA. GACA led to a decreased λ0.5 value for HPO-A, increased ,λ0.5 values for HPO-N, TPI-A and HPI, and a consistent λ0.5 value for TPI-N.

Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity

Metal-organic frameworks （MOFs） have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-I（also named Cu-BTC or MOF-199） was chemically reduced by doping it with alkali metals （Li, Na and K） and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction （XRD）, thermo-gravimetric analysis （TGA） and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li＋, Na＋ and K＋, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST- 1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

Adsorption of Folic Acid on the Single-walled Carbon Nanotubes: AIM and NBO Analyses via DFT

In the present work, the behavior of folic acid （FA） molecule adsorbed onto single-walled carbon nanotube （SWCNT） was examined using the DFT-B3LYP/6-31G＊ level. In order to obtain information about the binding features of SWCNT as adsorbent with FA molecule, several studies, including the structural and electronic parameters and also the Atoms in Molecules （AIM） analysis, were performed. It was observed that the FA molecule via hydrogen bond prefers to adsorb on SWCNT with adsorption energy of about -18.70 kcal/mol. The molecular orbitals （HOMO and LUMO）, natural bond orbital （NBO）,analysis, and density of states （DOS） plot indicated that a charge about 0.032 [ e [ is transferred from the FA molecule to the nanotube. After solvation energy calculations, it was found that the presence of a polar solvent causes an increase in FA adsorption on the single-walled carbon nanotube. Topological features such as electron energy density （Hc） and Laplacian of the electron density （V2p~） demonstrate partial covalent nature for H（ll6）...O（10） interaction in the FA/SWCNT complex. According to the calculated results, the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.

Characterization and Methanol Adsorption of Walnutshell Activated Carbon Prepared by KOH Activation

Walnut-shellactivated carbons（WSACs）were prepared by the KOH chemicalactivation.The effects of carbonization temperature,activation temperature,and ratio of KOH to chars on the pore development of WSACs were investigated.Fourier transform infrared spectroscopy（FTIR）,X-ray powder diffraction（XRD）,and scanning electron microscopy（SEM）were employed to characterize the microstructure and morphology of WSACs.Methanoladsorption performance onto the optimalWSAC and the coal-based AC were also investigated.The results show that the optimalpreparation conditions are a carbonization temperature of 700 ℃,an activation temperature of 700 ℃,and a mass ratio of 3.The BET surface area,the micropore volume,and the micropore volume percentage of the optimalWASC are 1636 m^2/g,0.641 cm^3/g and 81.97%,respectively.There are a lot of micropores and a certain amount of meso-and macropores.The characteristics of the amorphous state are identified.The results show that the optimalWSAC is favorable for methanoladsorption.The equilibrium adsorption capacity of the optimalWSAC is 248.02mg/g.It is shown that the equilibrium adsorption capacity of the optimalWSAC is almost equivalent to that of the common activated carbon.Therefore the optimalWSAC could be a potentialadsorbent for the solar energy adsorption refrigeration cycle.

Study on Adsorption of Formaldehyde by Modified Activated Carbon

By using potassium permanganate impregnation method,common activated carbon was processed in 0. 079 mol/L KMnO4 solution at 650℃ to obtain modified activated carbon loaded with manganese oxide,and then different quantities of common activated carbon and modified activated carbon were used to adsorb 0. 3 mg/m^3 formaldehyde. The results showed that carbon and manganese atoms on the surface of modified activated carbon could adsorb formaldehyde,and the removal rate of 0. 3 mg/m^3 formaldehyde by 30 g of modified activated carbon reached 80%,increased one time compared with that by common activated carbon. Different amounts of activated carbon had various effects on the adsorption of formaldehyde,and the best usage of common activated carbon and modified activated carbon was 100 and 30 g respectively.

Adsorption and Desorption of Gold on the Magnetic Activated Carbon

Adsorption and desorption of gold on the magnetic activated carbon (MAC) were investigated The adsorption rate of gold is higher than that of conventional coconut carbon in cyanide leach solution The loading gold can be easily desorbed as coconut carbon. Crushed fine magnetic carbon can be selected by a magnetic separator, It is suggested that the MAC can be used in carbon-in-pulp (CIP)process for increasing the recovery rate of gold

Adsorption Properties and Quantum Molecular Descriptors of the Folic Acid Drug Adsorbed onto Zigzag and Armchair Single Walled Carbon Nanotubes:DFT Simulations

The adsorption behavior of folic acid onto（5,0） zigzag and（5,5） armchair carbon nanotube（SWCNT） has been investigated using B3 LYP density functional at the 6-31G＊ level. The adsorption energies,molecular orbital analysis and structural changes at the adsorption site are indicative of covalent adsorption on the zigzag SWCNT surface,while the adsorption is physical on the armchair SWCNT surface. The density of states（DOS） Plot and the quantum molecular descriptors（QMD） are witness to the significant changes in the electronic properties of SWCNT systems after the attachment of adsorbed species to the tube surface. According to the calculated results,the single-walled carbon nanotubes are expected to be a potential efficient adsorbent for the adsorption of folic acid drug and also can be used as a suitable drug delivery vehicle within biological systems.

Mechanistic, Energetic and Structural Aspects of the Adsorption of Carmustine on the Functionalized Carbon Nanotubes

Using density functional theory, noncovalent interactions and two mechanisms of covalent functionalization of drug carmustine with functionalized carbon nanotube（CNT） have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug carmustine with functionalized CNT is thermodynamically suitable. NTCOOH and NTCOCl can bond to the NH group of carmustine through OH（COOH mechanism） and Cl（COCl mechanism） groups, respectively. The activation energies, activation enthalpies and activation Gibbs free energies of two pathways were calculated and compared with each other. The activation parameters related to COOH mechanism are higher than those related to COCl mechanism, and therefore COCl mechanism is suitable for covalent functionalization. COOH functionalized CNT（NTCOOH） has more binding energy than COCl functionalized CNT（NTCOCl） and can act as a favorable system for carmustine drug delivery within biological and chemical systems（noncovalent）. These results could be generalized to other similar drugs.

Prediction of Henry Constants and Adsorption Mechanism of Volatile Organic Compounds on Multi-Walled Carbon Nanotubes by Using Support Vector Regression

Support vector regression （SVR） combined with particle swarm optimization for its parameter optimization is employed to establish a model for predicting the Henry constants of multi-walled carbon nanotubes （MWNTs） for adsorption of volatile organic compounds （VOCs）. The prediction performance of SVR is compared with those of the model of theoretical linear salvation energy relationship （TLSER）. By using leave-one-out cross validation of SVR test Henry constants for adsorption of 35 VOCs on MWNTs, the root mean square error is 0.080, the mean absolute percentage error is only 1.19~, and the correlation coefficient （R2） is as high as 0.997. Compared with the results of the TLSER model, it is shown that the estimated errors by SVR are ali smaller than those achieved by TLSER. It reveals that the generalization ability of SVR is superior to that of the TLSER model Meanwhile, multifactor analysis is adopted for investigation of the influences of each molecular structure descriptor on the Henry constants. According to the TLSER model, the adsorption mechanism of adsorption of carbon nanotubes of VOCs is mainly a result of van der Waals and interactions of hydrogen bonds. These can provide the theoretical support for the application of carbon nanotube adsorption of VOCs and can make up for the lack of experimental data.

ADSORPTION OF SULFOXIDES ON SOLID FROM AQUEOUS SOLUTIONS——Ⅲ.THE ADSORPTION ON CARBON BLACK

The adsorption of decylmethylsulfoxide(DEMS)onto carbon black and the effects of temperature,salt(NaCl)and acid (HCl)have been measured.Typical two plateaux type adsorption isotherms were obtained.Applying the two step model of surfactant adsorption on solid/liquld interface and the general adsorption isotherm equation[9]the experimental results were interpreted qualitatively and quantitatively.

Comments on“Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al_2O_3 particles”

Recently, Hsieh and Horng [1] published the paper entitled as above. In section 3 results and discussion, the authors mentioned the first and the second order kinetic models without any quotations. In fact these two kinetic models have been published [2-5]. In order to distinguish a kinetics model based on the ad- sorption capacity of a solid from the one based on the concentration of a solution, Lagergren＇s first-order rate equation has been called pseudo-first-order [6-7]. The Lagergren＇s equation has been widely cited, but there are far more mistakes made in the quotation and in the reference section of papers, including the title, the author＇s name, journal title, year of publishing, volume, and page number [3]. In addition, the second order kinetic expression for the adsorption systems of divalent metal ions using sphagnum moss peat has been reported by Ho [8].

Experimental Design Technique on Removal of Hydrogen Sulfide using CaO-eggshells Dispersed onto Palm Kernel Shell Activated Carbon：Experiment,Optimization,Equilibrium and Kinetic Studies

This study presents the use of chicken eggshells waste utilizing palm kernel shell based activated carbon（PKSAC） through the modification of their surface to enhance the adsorption capacity of H2S. Response surface methodology technique was used to optimize the process conditions and they were found to be： 500 mg/L for H2S initial concentration, 540 min for contact time and 1 g for adsorbent mass. The impacts of three arrangement factors（calcination temperature of impregnated activated carbon（IAC）, the calcium solution concentration and contact time of calcination） on the H2S removal efficiency and impregnated AC yield were investigated. Both responses IAC yield（IACY, %） and removal efficiency（RE, %） were maximized to optimize the IAC preparation conditions. The optimum preparation conditions for IACY and RE were found as follows： calcination temperature of IAC of 880 ℃, calcium solution concentration of 49.3% and calcination contact time of 57.6 min, which resulted in 35.8% of IACY and 98.2% RE. In addition, the equilibrium and kinetics of the process were investigated. The adsorbent was characterized using TGA, XRD, FTIR, SEM/EDX, and BET. The maximum monolayer adsorption capacity was found to be 543.47 mg/g. The results recommended that the composite of PKSAC and Ca O could be a useful material for H2S containing wastewater treatment.

Preparation of Ammonia Adsorbent by Carbonizing and Activating Mixture of Biomass Material and Hygroscopic Salt

We put forward a new and ingenious method for the preparation of a new adsorbent by soaking, carbonizing and activating the mixture of hygroscopic salt and biomass material. The new adsorbent has high porosity, uniform distribution and high content of Ca Cl2, and exhibits high adsorption performance. The ammonia uptake and specific cooling power（SCP） at 5 min adsorption time can reach as high as 0.19 g·g^-1 and 793.9 W·kg^-1, respectively. The concept of utilizing the biomass materials and hygroscopic salts as raw materials for the preparation of adsorbents is of practical interest with respect to the potential quantity of biomass materials around the world, indicating that there would be a new market for biomass materials.Key words： biomass material; adsorption system; ammonia; calcium chloride; activated carbon

Characterization of P-nitrophenol Adsorption Kinetic Properties in Batch and Fixed Bed Adsorbers

P-nitrophenol（PNP） adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model（HSDM） based on external mass transfer and intraparticle surface diffusion was used to describe the adsorption kinetics for PNP in stirred batch adsorber at various initial concentrations and activated carbon dosages. The fixed bed model considering both external and internal mass transfer resistances as well as axial dispersion with non-linear isotherm was utilized to predict the fixed bed breakthrough curves for PNP adsorption under the conditions of different flow rates and inlet concentrations. The equilibrium parameters and surface diffusivity（Ds） were obtained from separate experiments in batch adsorber. The obtained value of Ds is 4.187×1012 m2/s. The external film mass transfer coefficient（kf） and axial dispersion coefficient（DL） were estimated by the correlations of Goeuret and Wike-Chang. The Biot number determined by HSDM indicated that the adsorption rate of PNP onto activated carbon in stirred batch was controlled by intraparticle diffusion and film mass transfer. A sensitivity analysis was carried out and showed that the fixed bed model calculations were sensitive to Ds and kf, but insensitive to DL. The sensitivity analysis and Biot number both confirm that intraparticle diffusion and film mass transfer are the controlling mass transfer mechanism in fixed bed adsorption system.

Application of Green Technology Using Biological Means for the Adsorption of Micro-Pollutants in Water

It is true that the world we have today is not the world we use to know. The Covid-19 pandemic has paralyzed all sector, hence the need for safety and enabling environment for mankind is of high importance. Adsorption technology is far the best and cheapest treatment technology for water and has extensively proven its worth for the uptake of micro-pollutant from surface, ground and water which are the major channels of home water. Over the years activated carbon is considered as the most common and universally used adsorbent for the eradication of different types of micro-pollutants from water. The contamination of surface water by micro-pollutant is a potential threat for the production of high quality and safe drinking water. Adsorption operation onto granulated activated carbon (GAC) in fixed-bed filters is often applied as a remedying step in the synthesis of safe and drinkable water. Activated carbon actively tends to act as a carrier material for a thin usually resistant layer of microorganisms (mostly bacteria) that forms on the coat of various surfaces (biofilm), hence biological simplification can be an alternative removal approach that can be adopted in granulated activated carbon filters. To evaluate the capacity of biofilm to biologically simplify micro-pollutants, it is very imperative to distinguish adsorption from biological simplification (biodegradation) as a removal mechanism. Experiment was carried out under the operating condition of a temperature range of 6?C to 20?C with biologically activated and autoclaved GAC to assess the biological simplification by the biofilm adsorbed on the GAC surface. Five micro-pollutants were selected as model compounds, of which some of them were biologically simplified by the GAC biofilm. Additionally, we observed that temperature can increase or decrease adsorption. Conclusively, comparison was made on the adsorption capacity of granulated activated carbon used for more than 50,000 beds.

Adsorption of benzene, cyclohexane and hexane on ordered mesoporous carbon

Ordered mesoporous carbon（OMC） with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound（VOC）disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.

Effective adsorption of sulfamethoxazole, bisphenol A and methyl orange on nanoporous carbon derived from metal-organic frameworks

Nanoporous carbons（NPCs） derived from metal–organic frameworks（MOFs） are attracting increasing attention in many areas by virtue of their high specific surface area, large pore volume and unique porosity. The present work reports the preparation of an NPC with high surface area（1731 m^2/g） and pore volume（1.68 cm^3/g） by direct carbonization of MOF-5. We examined the adsorption of three typical contaminants from aqueous solutions, i.e., sulfamethoxazole（SMX）,bisphenol A（BPA） and methyl orange（MO）, by using the as-prepared NPC. The results demonstrated that NPC could adsorb the contaminants effectively, with adsorption capacity（qm） of 625 mg/g（SMX）, 757 mg/g（BPA） and 872 mg/g（MO）, respectively. These values were approximately 1.0-3.2 times higher than those obtained for single-walled carbon nanotubes（SWCNTs） and commercial powder active carbon（PAC） under the same conditions. With its high surface area and unique meso/macropore structure, the enhanced adsorption of NPC most likely originates from the cooperative interaction of a pore-filling mechanism, electrostatic interaction,and hydrogen bonding. In particular, the p H value has a crucial impact on adsorption, suggesting the significant contribution of electrostatic interaction between NPC and the contaminants. This study provides a proof-of-concept demonstration of MOF-derived nanoporous carbons as effective adsorbents of contaminants for water treatment.

Effect of co-existing organic compounds on adsorption of perfluorinated compounds onto carbon nanotubes

Co-existing organic compounds may affect the adsorption of perfluorinated compounds （PFCs） and carbon nanotubes in aquatic environments. Adsorption of perfluorooctane sulfonate （PFOS）, perfluorooctane acid （PFOA）, perfluorobutane sulfonate （PFBS）, and perfluor- ohexane sulfonate （PFHxS） on the pristine multi-walled carbon nanotubes （MWCNTs-Pri）, carboxyl functionalized MWCNTs （MWCTNs-COOH）, and hydroxyl functiona- lized MWCNTs （MWCNTs-OH） in the presence of humic acid, 1-naphthol, phenol, and benzoic acid was studied. Adsorption kinetics of PFOS was described well by the pseudo-second-order model and the sorption equilibrium was almost reached within 24 h. The effect of co-existing organic compounds on PFOS adsorption followed the decreasing order of humic acid 〉 1-naphthol 〉 benzoic acid〉phenol. Adsorbed amounts of PFOS decreased significantly in the presence of co-existing or preloaded humic acid, and both adsorption energy and effective adsorption sites on the three MWCNTs decreased, resulting in the decrease of PFOS adsorption. With increasing pH, PFOS removal by three MWCNTs decreased in the presence of humic acid and phenol. The adsorbed amounts of different PFCs on the MWCNTs increased in the order ofPFBS 〈 PFHxS 〈 PFOA 〈 PFOS. The increase of both initial concentrations and the number of aromatic rings of co-existing organic compounds suppressed PFOS adsorption on the MWCNTs.

Novel Al-doped carbon nanotubes with adsorption and coagulation promotion for organic pollutant removal

Al-doped carbon nanotubes（Al-doped CNTs） were prepared as a multifunctional integrated material of adsorbent and coagulant aid for organic pollutant removal from aqueous solution. It was observed that aluminum species were dispersed homogeneously on the surface of CNTs, and mainly anchored onto defect structures of the CNTs. The introduction of aluminium efficiently improved adsorption ability for methyl orange（MO） onto the CNTs,and maximum adsorption capacity calculated from the Langmuir isotherm model can reach 69.7 mg/g. The MO adsorption kinetics can be better described by the pseudo-second-order and pore diffusion kinetic models, and the diffusion of MO anions into pores of the Al-doped CNT adsorbent should be the rate-determining step.Thermodynamic analyses indicated that the adsorption of MO onto Al-CNTs-2.0 was endothermic and spontaneous. Moreover, adsorption capacity for MO on the Al-doped CNTs was evidently dependent on the CNT dose, solution p H and adsorbent dose. From the perspective of low-cost and multifunctional, suspension obtained during the Al-doped CNT adsorbent preparation, was tested as coagulant to remove humic acid（HA）. A significant observation is that the suspension exhibited an excellent coagulation performance for HA,because abundant aluminous polymer and Al-doped CNTs existed in the suspension.