Nitrate Adsorption Capacity Research Articles

CTAB-Si Nanoparticles Derived from Rice Husk Ash for Nitrate Ions Removal in Simulated Wastewater

In this study, silica (Si) nanoparticles derived from rice husk ash is coated with cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and used as adsorbent of nitrate ion in wastewater. CTAB functionalized Si (CTAB-Si) nanoparticles were characterized using scanning electron microscope (SEM), energy dispersive X-Ray (EDX), dynamic light scattering (DLS) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The synthesized CTAB-Si nanoparticles has a non-spherical shape, with visible polydispersity and is amorphous with average particle size of 72nm. It showed stretching vibrations of silanol at 963cm-1, siloxane at 1073cm-1, sharp peaks at 2852cm-1 and 2922cm-1 due to the methylene tail of CTAB and amine peak at 1,384cm-1. An ∼80% nitrate removal and adsorption capacity of 7.98 mg NO3/g CTAB-Si nanoparticles was obtained at optimized condition using Face Centered Central Composite Design (FC-CCD) at pH 4, 50 mgL-1 of adsorbate concentration, 0.2 gL-1 adsorbent dose and 30 minutes contact time. The adsorption isotherm and kinetic models fits well in Langmuir model and Pseudo second order with a R2 of 0.984 and 0.999 respectively. The efficiency of the nanoparticle after 5 adsorption cycles was ∼50% nitrate removal.

Multifaceted application of modified biochar for water and wastewater treatment

AbstractBiochar, a carbon‐rich material produced through the pyrolysis of biomass, has been shown to have the potential to remove contaminants from water and wastewater. However, due to the weak adsorption capacity and narrow adsorption range of pure biochar, it is modified, either chemically or physically, in order to optimize its applications in water and wastewater treatment. This study summarizes the recent advancements in the application of modified biochar for water and wastewater treatment. Modification of biochar increases its surface area and porous structure, which makes it an effective adsorbent to immobilize a range of contaminants, such as heavy metals, dyes, and organic contaminants. It can also be used as a catalyst in the biodegradation of organic pollutants as it can provide a substrate for microbial growth and metabolism, enhancing pollutant degradation. This study also summarizes various biochar modifications such as gas, acid, alkali, metal, organic compounds, and oxidizing agents. Among the metal‐modified biochar, Iron‐modified biochar has shown the highest tetracycline (TC) removal efficiency (90.7%) and nitrate adsorption capacity (32.33 mg g−1). N‐doped biochars were found to be the most effective biochars for removing heavy metals such as Cd2+ or Cu2+ and aromatic compounds as they can increase the adsorption of raw biochar by up to 70%. Increasing the number of functional groups on the surface of the biochar by using organic compounds like acrylonitrile and chitosan showed a two to three‐fold increase in the adsorption capacity of pollutants such as Cd2+ and Hg2+. According to this review, modified biochar technology is a cost‐effective and environmentally friendly wastewater treatment method.

One-pot high-speed shear preparation of modified straw: An efficient, convenient, nontoxic, and green method with high adsorption capacity for nitrate removal from aqueous solution

The multistep modification of straw-based adsorbent materials has significant advantages in terms of adsorption capacity over the one-step method; however, it poses significant problems such as a complicated, time-consuming preparation process, low grafting efficiency, and widespread use of highly toxic reagents. This study presents the first application of the one-pot high-speed shear method (HSSM) for the efficient grafting of 2,3-epoxypropyltrimethylammonium chloride on wheat straw. Experimental results show that the grafting rate, BET surface area and preparation speed of HSSM increased by 4.96, 12.57 and 3.7–14.5 times, respectively, compared with those of the traditional one-step magnetic stirring heating method. The nitrate adsorption capacity was 65.45 mg g−1, which is similar to or better than that of the multistep quaternary ammonium–modified material. In addition, the proposed preparation process did not require additional heating and did not use any toxic reagents. Characterization through EDS, FTIR, Zeta, and XPS confirmed the adsorption mechanism to be ion exchange and electrostatic gravity, with the former contributing 73–79%. The proposed one-pot HSSM to prepare quaternary ammonium–modified straw is fast and simple, has high adsorption performance, and does not use highly toxic reagents. The adsorption capacity of the adsorbent remained 55.04–52.98 mg·g−1 in the range of pH 3–11. After nine adsorption and desorption cycles, the adsorption efficiency remained > 80% in the adsorbent regeneration test. This work is in accordance with the development of agricultural waste resources and green chemical development ideas.

Feasibility of nitrate adsorption from aqueous solution by nitrogen and oxygen-modified pine bark biochar: experimental and computational approach

Efficient and economical wastewater treatment has presented itself as a global challenge. In this context, adsorption is one of the most effective methods to remove contaminants from wastewater. The present study evaluated the feasibility of chemically modified pine bark biochar’s nitrate adsorption ability. Pine bark biochar was modified with urea and sulfuric acid to remove nitrate from an aqueous solution. The physicochemical properties of the biochar samples, such as pH, pH at point of zero charges, surface atomic composition, surface morphology, and surface area, were evaluated. The equilibrium adsorption data were fitted to the Langmuir and Freundlich isotherm models. The kinetic data were fitted to different kinetic models (pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich). The adsorption data fitted well with the Langmuir and pseudo-first order models. The maximum nitrate adsorption capacity was found to be 1.548 mg g−1. Mass transfer studies were conducted to identify the rate-limiting step, values of the external mass transfer coefficient, and diffusion coefficient in the nitrate adsorption process by the modified biochar. The external mass transfer coefficients were in the range of 2.2 × 10–11–2.86 × 10–10 m s−1. The intraparticle diffusion coefficient ranged from 6.53 × 10–10 to 1.78 × 10–9 m2 s−1. The Biot number value less than 100 indicated that the adsorption was controlled by film diffusion. Interaction energies between nitrate ions and model biochar structures were calculated DFT-based quantum chemical software (Gaussian). The positive interaction energy values (2.3485–2.485 eV) suggested nitrate adsorption on model biochar structures was thermodynamically not feasible.Graphical

Study on adsorption of ammonium and nitrate in wastewater by modified biochar

This study investigates the prepared rice husk biochar (RHB) and Mg/Ca-LDHs@RH biochar (MCB) microstructural, morphological, and nitrate adsorption capacity, owing to the increased concentration of nitrate ions in industrial wastewater that lead to serious environmental problems. In this study, biochar was prepared from agricultural waste, and the co-precipitation method was integrated to prepare Mg/Ca-rich layered double hydroxides (Mg/Ca-LDHs). The prepared biochar physicochemical characteristics were analyzed using XRD, FESEM, EDS, BET, and IC. Here we further investigated the influence of pyrolysis temperature and different concentrations (Mg, Ca) LDHs coatings. This study found that the pyrolysis temperature reduces the biochar yield percentage from 44.5 to 30.2 %. The biochar pores are shown in a honeycomb shape, and the diameter of the pores is about 3–5 μm. In addition, the obtained biochar pores seemed to be more fragmented as the Mg/Ca ratio gradually increased. The surface area of biochar increased with the increase in the Mg/Ca ratio, and the specific surface area of 3:1 and 4:1 Mg/Ca-LDHs ratio was the highest, reaching about 288–308 cm2/g. The biochar LDHs with a 3:1 Mg/Ca-LDHs ratio can effectively adsorb nitrate ions in water, and the LDHs maintain a stable state during the adsorption process.

A novel ion-imprinted polymer based on the principle of ion exchange by bulk polymerization for specific recognition and adsorption of nitrate in polluted groundwater

A novel NO3− ion imprinted polymer (IIP-NO3−) was successfully synthesized based on the principle of “ion exchange” and the method of “bulk polymerization”. The NO3− anions, cationic monomers dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) was used as template ions and functional monomers respectively. The material characterization showed that IIP-NO3− has an irregular porous structure. The maximum nitrate adsorption capacity of IIP-NO3− on NO3− was 48.486 mg/g under an optimal preparation condition. The isothermal adsorption (R2 = 0.9947) of IIP-NO3− for NO3− basically conformed to the Langmuir model. The adsorption process followed with the pseudo-secondary order kinetic model (R2 > 0.99), and it can reach equilibrium within 5 min. The IIP-NO3− had an obviously lower adsorption capacity for another common anion NO2−, HCO3−, SO42− ions in groundwater pollution than NO3− ions. The recognition selectivity coefficient of IIP-NO3− for NO3− ions were 2.839, 6.450, 1.773 respectively due to the imprinted effect. And this ion imprinted polymers with high selectivity to nitrate can be combined with the chemical reduction and the electrochemical reduction method, so as to improve the nitrate chemical reduction efficiency and reduce the regeneration cost of the IIP-NO3−.

Bamboo Chopstick Biochar Electrodes and Enhanced Nitrate Removal from Groundwater

The nitrate pollution of groundwater can cause serious harm to human health. Biochar electrodes, combined with adsorption and electroreduction, have great potential in nitrate removal from groundwater. In this study, bamboo chopsticks were used as feedstocks for biochar preparation. The bamboo chopstick biochar (BCBC), prepared by pyrolysis at 600 °C for 2 h, had a specific surface area of 179.2 m2/g and an electrical conductivity of 8869.2 μS/cm, which was an ideal biochar electrode material. The maximum nitrate adsorption capacity of BCBC-600-2 reached 16.39 mg/g. With an applied voltage of 4 V and hydraulic retention time of 4 h, the nitrate removal efficiency (NRE) reached 75.8%. In comparison, the NRE was only 32.9% without voltage and 25.7% with graphite cathode. Meanwhile, the average nitrate removal rate of biochar electrode was also higher than that of graphite cathode under the same conditions. Therefore, biochar electrode can provide full play to the coupling effect of adsorption and electroreduction processes and obtain more powerful nitrate removal ability. Moreover, the biochar electrode could inhibit the accumulation of nitrite and improve the selectivity of electrochemical reduction. This study not only provides a high-quality biochar electrode material, but also provides a new idea for nitrate removal in groundwater.

Facile copolymerization synthesis of vinylimidazole/dibromodecane/vinylpyridine polymer with high capacity for selective adsorption of nitrate from water

In this study, a novel polymer 1-vinylimidazole/1,10-dibromodecane/4-vinylpyridine polymer (VDV) with high nitrate adsorption capacity and selectivity was synthesized using a facile copolymerization method. The maximum nitrate adsorption capacity of VDV reached 52.6 mg N/g, which was 54.17 % and 52.42 % higher than those of 1-vinylimidazole/1,10-dibromodecane and 4-vinylpyridine/1,10-dibromodecane, respectively. For the co-existing anions interference, dibromodecane improved the hydrophobicity of VDV; thereby, reducing the sulfate interference on nitrate adsorption that the nitrate adsorption capacity in sulfate (250 mg/L)/nitrate (56.4 mg N/L) binary solution still reached 77.2 % of the control group (56.4 mg N/L of nitrate alone). When sulfate concentration increased from 150 to 350 mg/L in sulfate/nitrate (56.4 mg N/L) binary solution, nitrate adsorption capacity dropped from 88 % to 55.2 % of the control group. Meanwhile, the adsorption selectivity (Ke/c) for nitrate was higher than 1 (Ke/c = 1.3–2.6), indicating that VDV still has adsorption affinity to nitrate in companion with a high concentration of sulfate. For chloride and bicarbonate (150–350 mg/L), they almost had no interference with nitrate adsorption. Besides, the adsorption process is preferably fitted with the pseudo-second-order kinetics (R2 = 0.992) and the Freundlich model (R2 > 0.99), indicating that the process is multilayer chemisorption. After five times recycle, nitrate adsorption capacity maintained above 91 % of that of the first cycle, indicating the stable reusability of VDV, and it exhibited excellent nitrate adsorption from real wastewaters. Therefore, with a conspicuous enhancement of adsorption capacity and selectivity for nitrate, VDV is promising in nitrate removal from waters.

Using ZrO2 coated sludge from drinking water treatment plant as a novel adsorbent for nitrate removal from contaminated water

This study aimed to produce a novel efficient absorbent using sludge generated from drinking water treatment plants (DWTPs) as a low-cost absorbent and applied to treat nitrate (NO3−) from contaminated water. Before the ZrO2 coating experiment, the drinking water sludge (DWS) from DWTPs was pretreated by thermal treatment (80 °C, 200 °C, and 500 °C). After that, ZrO2 coated drinking water sludge (DWS@ZrO2) was produced by a simple precipitated reaction. The synthesized DWS@ZrO2 was characterized by FTIR, SEM, and EDS with mapping analysis, XRD, and VSM. The results revealed that DWS@ZrO2 could improve the pore filling in the adsorption experiment. The highest nitrate adsorption capacity was achieved (30.99 mg g− 1) at pH 2 with DWS500@ZrO2. Adsorption kinetics indicated that pyrolyzed DWS at 500 °C provided the highest nitrate adsorption capacity, followed by 200 °C, and 80 °C. Thermodynamic results showed that the obtained nitrate removal was an endothermic and spontaneous process. The possible nitrate adsorption mechanism of DWS@ZrO2 could mainly involve pore filling, electrostatic interaction, and ligand exchange. The experimental results suggest that DWS@ZrO2 is a feasible absorbent with high-efficiency, low-cost, high recyclability, and eco-friendly characteristics for treating nitrate in an aqueous solution.

Cationic microcrystalline cellulose - Montmorillonite composite aerogel for preconcentration of inorganic anions from dairy wastewater.

Development of efficient adsorbents to inorganic anions as a solid phase extraction (SPE) material is highly desirable for chromatographic analysis and pollution control. In this work we developed a new hybrid cationic microcrystalline cellulose aerogel composite. Cationic cetylpyridinium imbedded montmorillonite (CPC-MT) was uniformly entrapped in microcrystalline cellulose (MCC) to enhance anionic adsorption efficiency and mechanical stability. The developed CPC-MT@MCC aerogel was used as an SPE adsorbent for anions from dairy wastewater by coupling with ion-column chromatography. Further quaternized CPC-MT@MCC aerogel (CPC-MT@QMCC) showed unique low density (10.6mgcm-3), large specific surface area (320m2g-1), porosity 70%, 800mgg-1 nitrate adsorption capacity within 60min and ease of elution in alkaline solutions. The CPC-MT@QMCC aerogel showed efficient regeneration and reuse performances for up to 10 cycles. More importantly, a dynamic binding efficiency of 710mgg-1 highlights its excellent performance for practical applications. 96% of nitrate anion from environmental manure wastewater samples were adsorbed with 98.7% recovery. A good linear relationship was obtained in the range of 0.01-10mgL-1 and the limits of detection was 0.5mgL-1 using CPC-MT@QMCC aerogel as a preconcentration column. The successful synthesis of such intriguing and economic CPC-MT@QMCC aerogel may provide a promising matrix for high-performance and high efficiency chromatographic media.

The use of recycled materials in a biofilter to polish anammox wastewater treatment plant effluent

Anammox is gaining popularity for treating wastewater containing high-strength ammonia due to lower energy demand compared to conventional nitrification-denitrification processes; however, anammox is reported to increase nitrate loads in the effluent. The objective of this study was to assess the applicability of recycled materials [recycled concrete aggregate (RCA) and rice husks (RH)] as a polishing step to improve anammox reactor effluent quality. Anammox effluents were separately passed through two single-stage columns containing RCA and RH, and one two-stage column (50% RCA, 50% RH) to quantify total N, ammonia, nitrate, nitrite, and phosphate removal efficiencies. Langmuir isotherm experiments were conducted to quantify nitrate, nitrite, and phosphate sorption capacities in the columns. The RCA column exhibited the highest phosphate sorption capacity (0.074 mg/g), while the RH column exhibited higher nitrite and nitrate adsorption (0.063 mg/g and 0.023 mg/g respectively). We created a Hydrus-1D model to estimate pseudo-first-order reaction rates in the columns. Because RCA media can form metal-phosphate precipitates, the fastest phosphate reaction rate (1.58 min−1) occurred in the RCA column. The two-stage column demonstrated the greatest overall removals for all nutrients, and removal rates were consistent throughout the experimental period. The two-stage column achieved 15% total N, 94% ammonia-N, 38% nitrate-N, 75% nitrite-N, and 27% phosphate removal. The maximum nitrite, nitrate, and phosphate adsorption capacities in the two-stage column were 0.030 mg/g, 0.017 mg/g, and 0.014 mg/g respectively. This is the first study to demonstrate that recycled materials can successfully be integrated into a biofilter as an effluent polishing step to remove nutrients from anammox wastewater.

Application of Modified Spent Mushroom Compost Biochar (SMCB/Fe) for Nitrate Removal from Aqueous Solution.

The public is already aware that nitrate pollution caused by nutrient runoff from farms is harmful to aquatic life and human health, and there is an urgent need for a product/technology to solve this problem. A biochar adsorbent was synthesized and used to remove nitrate ions from aqueous media based on spent mushroom compost (SMC), pre-treated with iron (III) chloride hexahydrate and pyrolyzed at 600 °C. The surface properties and morphology of SMCB/Fe were investigated using Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of main parameters such as the adsorbent dosages, pH of the solutions, contact times, and ion concentrations on the efficiency of nitrate removal was investigated. The validity of the experimental method was examined by the isothermal adsorption and kinetic adsorption models. The nitrate sorption kinetics were found to follow the pseudo-second-order model, with a higher determination coefficient (0.99) than the pseudo-first-order (0.86). The results showed that the maximum percentage of nitrate adsorption was achieved at equilibrium pH 5–7, after 120 min of contact time, and with an adsorbent dose of 2 g L−1. The highest nitrate adsorption capacity of the modified adsorbent was 19.88 mg g−1.

Recycling rice husk for removal of phosphate and nitrate from synthetic and swine wastewater: Adsorption study and nutrient analysis of modified rice husk

The objective of this study was to determine the adsorbent potential of rice husk and its modified form for phosphate and nitrate removal from synthetic and swine-farm wastewater. The mechanism of adsorption as well as the potential of phosphate-/nitrate- adsorbed rice husk as nutrient rich residue was also investigated. Two-step modification of RH (using base-washing (BW) and chemical modification (CM) was conducted to compare the phosphate and nitrate removal. The effects of several factors (pH, sorbent dosage, contact time, initial concentration, and coexistence of both ions) were investigated to gain insight into the adsorption rate, behavior, and mechanism of the modified RH regarding phosphate and nitrate removal. The results of Fourier-transform infrared spectroscopy showed that the modification was successful by crosslinking with the amine group of the chemical agent. Fitting the adsorption kinetic data of phosphate showed physical adsorption, intraparticle diffusion, and chemisorption, whereas for nitrate, the data indicated mainly chemisorption. Fitting the adsorption isotherm data of phosphate and nitrate together showed adsorption on a monolayer coating of anions on the homogeneous sorbent’s surface. The maximum phosphate and nitrate adsorption capacities were 6.94 and 2.46 mg/g, respectively, for a single adsorbate and 11.14 and 1.76 mg/g, respectively, for the binary solution. In real swine wastewater, removal efficiencies of phosphate, nitrite, nitrate, sulfate, and ammonia were 83.8%, 65.0%, >45.0%, 36.6%, and 2.6%, respectively, indicating that the modified RH would be effective for phosphate and nitrate removal from real wastewater. Finally, nutrient analysis of the phosphate- and nitrate-sorbed RH showed increases in nitrogen and phosphorus, which would be beneficial for further use of the RH as nutrient or fertilizer after adsorption.

Optimization of Nitrate and Nitrite Anions Adsorption on Modified Silica using Batch Method

Ammonia inorganic compounds are compounds that are often found because it is soluble in ground water which causes health hazards that are carcinogenic, mutagenic, tetratogenic and cause metamoglobinemia. Ammonia compounds that have negative effects on humans are nitrate and nitrite anions. Disposal of liquid waste and the use of fertilizers cause nitrates and nitrites to dissolve so that it has a negative impact on groundwater. One of the efforts to overcome nitrate and nitrite in waste is by adsorping with adsorbent., where the adsorbent used is DMA modified silica. Characterization by adsorption of nitrites and nitrates from aqueous solution at various pH, concentrartions, and contact times. The result showed that silica modification with DMA increased the adsorption capacity of nitrates and nitrtites. The Langmuir isotherm yields a regression coefficient R2 = for 0.9809 for nitrate and 0.9469 for nitrite. Nitrate adsorption capacity of 0.1669 mg g-1 with an initial nitrate concentration of 60 ppm at pH 8 with stirring for 120 minutes while the maximum adsorption capacity of nitrite was 0.1669 mg g-1 with an initial nitrite concentration of 40 ppm at pH 6 with stirring for 120 minutes.

Study on adsorption of nitrate ion from biogas effluent by melaleuca biochar

Contamination of water resources by nitrate has become an important problem in recent decades. Although nitrate is not toxic, it can be converted into nitrite and cause serious harm to human health. One of the most effective methods of nitrate removal is the use of adsorbents. The objective of this study was to evaluate the nitrate adsorption efficiency from biogas solution by using melaleuca biochar that was pyrolysed at 700oC. Physical and chemical characteristics of melaleuca biochar were determined using a variety of methods including scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) test. Nitrate concentration was measured using a UV spectrophotometer with a wavelength of 660 nm. The results showed that the optimum conditions for the effective adsorption of nitrate ion onto melaleuca biochar were found to be pH 4, biochar dosage of 1 g L-1, and retention time of 15 min. The experimental data were fitted to different adsorption isotherms models (Langmuir, Freundlich models). The maximum nitrate adsorption capacity of melaleuca biochar was 15.5 mg g−1.

Nitrate Adsorption capacity of Activated Gamalama Volcanic Ash

<p>The adsorption process of nitrate from an aqueous solution by using activated Gamalama volcanic ash was investigated. Gamalama volcanic ash (VA) was activated with HNO3 2M. The effect of adsorbent mass and initial nitrate concentration on nitrate adsorption were observed in this study. The adsorption process was conducted using a various mass of adsorbent (1 g, 2 g, 4 g, 6 g, and 8 g), various initial concentrations of nitrate (20 mg/L, 30 mg/L,40 mg/L, 50 mg/L, and 60 mg/L). The increasing of adsorbent mass decreased the adsorption capacity was observed. It was also found that the increase in initial concentration increased the adsorption capacity. The highest nitrate adsorption capacity showed by 1 gram adsorbent for 0.167 mg/g, and at nitrate initial concentration 80 mg/L, for 1.831 mg/g. Adsorption isotherm of nitrate on activated VA was determined and figured. These isotherms were modelled according to Freundlich and Langmuir adsorption isotherm.</p>

Synthesis and surface-functionalizing of ordered mesoporous carbon CMK-3 for removal of nitrate from aqueous solution as an effective adsorbent

In this study, the adsorption of nitrate onto ordered mesoporous carbon CMK-3 was investigated. First, CMK-3 was synthesized and then directly amino-functionalized by 3-aminopropyl trimethoxysilane (APTMS). The physicochemical properties of as-prepared adsorbent were characterized by XRD, EDS-SEM, FT-IR and N2 adsorption-desorption. Ultraviolet/visible spectroscopy was used to evaluate the adsorbent ability for nitrate reduction. In batch experiments, the influence of effective parameters such as contact time, adsorbent dosage, solution pH, initial concentration and temperature was investigated on the nitrate adsorption capacity. The obtained results indicated 100% removal efficiency for initial nitrate concentration of 50 mg l−1 and 78% for the concentration of 100 mg l−1, at low adsorbent dosage (3 g l−1) and very fast equilibrium attainment (5 min) without pH dependency (in the range of 2.0–8.0). The maximum nitrate adsorption capacity of Amino-CMK-3 was 48.78 mg g−1 in the concentration range of 50–250 mg g−1. Kinetic studies confirmed that the process followed a pseudo-second-order and that the Langmuir isotherm best fitted the equilibrium adsorption of nitrate. Nitrate desorption occurred after a reasonable time (3 h) and confirmed the adsorbent reusability without further treatment. The higher adsorption capacity of CMK-3 stemmed from its incredible mesoporous structure, including nano-channels that were completely functionalized by amino groups. Grafting aminopropyl groups potentially turned the CMK-3 to a promising adsorbent for nitrate removal.

Composite MWCNT/ MIL-101 (Cr)/CaCl2 as High-Capacity Water Adsorbent for Long-Term Thermal Energy Storage

Mil-101 (Cr) material is considered to be one of the most potential thermochemical energy storage materials in recent years. It has the advantages of a typical S-type water adsorption isotherm. Has low working temperature and large water adsorption amount. However, the adsorption properties of the material need to be improved under low water pressure. To improve the performance, the acidified MWCNTs were added before the hydrothermal reaction of mil-101 (Cr) materials to optimize the micropore structure. After the preparation, the new composite thermochemical energy storage materials were prepared by impregnation with a certain concentration of calcium chloride aqueous solution. The effects of multi-walled carbon nanotubes and calcium chloride on the physical and chemical properties of the materials were discussed. Through X-ray diffraction experiment, scanning electron microscope, microstructure analysis, nitrogen adsorption capacity test, water adsorption capacity test, and other means, the micro characteristics, pore structure, crystal morphology, and chemical composition of the materials were characterized, and the water adsorption performance of the materials was synthesized. The experimental results show that the addition of carbon nanotubes can improve the pore properties of the materials so that the porous organic skeleton can accommodate more calcium chloride particles. The composite materials with calcium chloride can provide excellent hydrophilicity and high water adsorption capacity. Also, the water absorption rate and adsorption-desorption cycle capacity of the material have been significantly improved. The experimental results show that when the mass fraction of calcium chloride reaches 30% when 90 mg acidified MWCNTs are added into every four chromium nitrate crystals, the hydrophilicity and adsorption capacity of the composite can reach a high equilibrium state. At the same time, the experimental yield of the material is high, the product is easy to obtain, the environmental friendliness is also reflected, so it is expected to become the adsorption heat pump thermochemical energy storage material with research potential.

Surface characterization of mesoporous biomass activated carbon modified by thermal chemical vapor deposition and adsorptive mechanism of nitrate ions in aqueous solution

The mesoporous activated carbon derived from moso biomass was selected to be modified to efficiently and rapidly remove aqueous phase nitrate ions. The bamboo was activated by H3PO4 and pyrolyzed at 500℃, marked as BAP6. Via various steps including thermal chemical vapor deposition (CVD), 7 types of surface modified biochar were obtained. Surface characterization of all the samples was investigated by Brunauer-Emmett-Teller method, elemental analyzer, and X-ray photoelectron spectroscopy. The quaternary nitrogen (N–Q) as strong adsorptive sites was deposited successfully on the surface of BAP6 (Davg = 6.8 nm, SBET = 1024 m2/g) by CVD doping nitrogen on it. The optimal modified mesoporous activated carbon BAP-8AN20-9.5HT30-8ST30 (Davg = 4.4 nm, SBET = 995 m2/g) owned nitrate adsorption capacity of 0.46 mmol/g in nitrate concentration of 200 mg/L at solution pH 3 and surface adsorption rate of 0.47 μmol/m2. The adsorption principle was also discussed. Adsorption kinetics were examined and analyzed by the pseudo-first-order and pseudo-second-order model. All powdery samples BAP6-8AN20-9.5HT30-8ST30 and reference samples KF-8ST10-8AN20-9.5HT30-8ST30 and HP555 were fitted by second-order model well (R2 = 0.995, 0.999 and 0.999). The results showed that BAP-8AN20-9.5HT30-8ST30 was the most rapid adsorbent to arrive at equilibrium, which took only 8 min with a Qe of 0.43 mmol/g.

Adsorption capacity of nitrate from artificial fertilizers and soil on pyrophyllite

The study at hand presents for the first time the use of pyrophyllite as adsorbent for nitrate removal from soil and artificial fertilizers. A series of column and batch adsorption experiments were conducted to examine the effects of the adsorbent’s various parameters, the contact time, pH of the solution, the initial concentration of nitrate, concentration and adsorbent granulometry. Pyrophyllite fractions of 0.25, 0.50 and 1.00 mm had very similar pH values of aqueous suspensions and were in the weakly basic range. Nitrate adsorption capacity on pyrophyllite expressed by recovery factor values ranges from 93.14 to 99.77%. High recovery factor values from 90.44 to 97.45% for 1, 3, 5 and 8 mL min−1 flow rates were obtained using all pyrophyllite fractions. Nitrate removal was very effective by the contact time of 1 and 2 h, and the recovery factor values were in the range of 90.38–91.47% and 92.15–93.18% for a contact time of 1 h and 2 h, respectively. In addition, elution of nitrate from pyrophyllite was performed using the following solution with different pH values: 1.70 (synthetic gastric juice), 6.40 (rainwater), 7.70 (distilled water), 9.30 and 12.50 (NaOH solution). Elution was very low for all used solutions and was the highest at the pH 9.30. The results show that the use of pyrophyllite for removal of nitrate from artificial fertilizers and soil was an adequate approach because it has a high nitrate adsorption capacity, while the nitrate elution from the pyrophyllite was very low.