Adsorption of phosphate by the cellulose-based biomaterial and its sustained release of laden phosphate in aqueous solution and soil

Phosphate adsorption characteristics of CeO2-loaded, Eucommia ulmoides leaf residue biochar

In this study, a Ce-loading biochar (Ce-BC) was synthesized by the optimal modification method of pre-pyrolysis impregnation, a pyrolysis temperature at 600 °C, and a CeCl3 concentration of 1.00 mol L-1 for efficient adsorption phosphorus (P) from wastewater. The results revealed that Ce-BC could achieve a maximum P removal rate of 100% under specific conditions: an adsorbent concentration of 2.00 g L-1, an initial solution pH of 3.00, an adsorption temperature of 25 °C, and an initial P concentration of 20.00 mg L-1. The adsorption process followed the quasi-secondary kinetic model, suggesting the Ce-BC was particularly effective in acidic environments. Meanwhile, Ce-BC has a strong resistance to anion interference and good cycling performance (the P adsorption capacity of Ce-BC was 59.77% of its initial value after four cycles). Field emission scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) indicated that Ce-BC contained a porous structure and rich functional groups (hydroxyl and carboxyl), and compounds of CeO2 and MgCeO3 were formed. The Ce loading favored the exchange with P through ligands, inner-sphere complexation, ion exchange, and electrostatic interaction to form inner-sphere complex-cerium P (CePO4), and the surface complex of Ce-O-P replaced O-H. In addition, the Ce-BC adsorption columns substantially affected P removal in actual wastewater. Overall, Ce-BC is a promising material for the treating P-containing acidic wastewater.

Modified lignin can achieve mitigation of ammonia and greenhouse gas emissions simultaneously in composting

The constant ammonia gas (NH3) and greenhouse gases (GHG) emissions were considered as a deep-rooted problem in composting which caused air pollution and global climate change. To achieve the mitigation of NH3 and GHG, a novel additive derived from wasted straw, with modified structure and functional groups, has been developed. Results showed that the adsorption capacity of modified lignin (ML) for both ammonium and nitrate was significantly increased by 132.5-360.8 % and 313.7-454.3 % comparing with biochar (BC) and phosphogypsum (PG) after reconstructing porous structure and grafting R-COOH, R-SO3H functional groups. The application of ML could reduce 36.3 % NH3 emission during composting compared with control. Furthermore, the synergetic mitigation NH3 and GHG in ML treatment resulted in a reduction of global warming potential (GWP) by 31.0-64.6 % compared with BC and PG. These findings provide evidence that ML can be a feasible strategy to effectively alleviate NH3 and GHG emissions in composting.

Polyethylene glycol crosslinked modified chitosan/halloysite nanotube composite aerogel microspheres for efficient adsorption of melanoidin

Melanoidins are widely present in molasses wastewater and are dark-colored macromolecules that are hazardous to the environment. Currently, adsorption methods can effectively remove melanoidins from wastewater. However, existing adsorbents have shown unsatisfactory removal efficiency for melanoidins, making practical application challenging. Polyethylene glycol crosslinked modified chitosan/halloysite nanotube composite aerogel microspheres (PCAM@HNTs) were developed as a highly efficient adsorbent for melanoidins. The removal rate of PCAM@HNTs for melanoidins was 98.53 % at adsorbent dosage 0.4 mg/mL, pH 7, temperature 303 K and 450 mg/L initial melanoidins concentration, and the corresponding equilibrium adsorption capacity was 1108.49 mg/g. The analysis results indicate that the adsorption of melanoidins by PCAM@HNTs is a spontaneous and endothermic process. It fits well with pseudo-second-order kinetic models and the Freundlich isotherm equation. The adsorption of PCAM@HNT on melanoidins is primarily attributed to electrostatic and hydrogen bonding interactions. Furthermore, PCAM@HNTs exhibit excellent biocompatibility and are nonhazardous. Therefore, PCAM@HNTs proved to be an ideal adsorbent for the decolorization of molasses wastewater.

Comparative Investigation of Phosphate Adsorption Efficiencies of MOF-76 (Ce) and Metal Oxides Derived from MOF-76 (Ce)

Phosphate pollution is a very challenging problem for the water environment. Phosphate mixed with water in various ways causes eutrophication. To sustain life in aquatic systems, phosphate ions must be cleaned. Therefore, it is very important to remove phosphate in wastewater. Here, an adsorption method has been tried for the removal of phosphate. MOF-76 (Ce), a cerium-based metal-organic framework, was synthesized by a hydrothermal method. Since metal oxides are known to be successful in phosphate adsorption, CeO2 nanoparticles were also obtained by pyrolysis of this MOF structure. The phosphate adsorption efficiencies of both adsorbents were compared. The characterization methods (SEM, FTIR, XRD, and TGA) were applied to adsorbents. The kinetic, isotherm, and thermodynamics studies were applied to experimental results. At 298 K, the adsorption capacity of MOF-76 (Ce) is higher than that of CeO2, according to Langmuir isotherm qm values. The qm values are 72.97 and 55.71 mg/g, respectively. Both adsorbents follow the pseudo second-order kinetic model. It has been found that MOF-76 (Ce) has a pH-selective property in phosphate adsorption. No change was observed in the phosphate adsorption capacity of CeO2 with pH. In terms of thermodynamics, the endothermic reaction is valid for both adsorbents.

Phosphorus recovery from agricultural waste via cactus pear biomass

In this study, the potential of cactus pear pruning waste (CPPW) as a low-cost adsorbent biomass for phosphorus (P) removal from aqueous solutions was investigated in batch mode. Biomass samples derived from cactus pear were collected and analyzed to investigate their properties when enriched with either calcium (Ca) or iron (Fe). The examination focused on the capacity of these samples to remove P. The P removal capacities were determined to be 2.27 mg g-1, 1.33 mg g-1, and 1.87 mg g-1 for Ca2+-enriched, Fe2+-loaded, and Fe3+-loaded biomass respectively. Among the various models studied, the Langmuir isotherm model was identified as the most appropriate for accurately describing the P adsorption the enriched biomass. The kinetics of the adsorption process were analyzed by applying the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The pseudo-second-order model provided the best fit to the experimental data. Furthermore, the desorption and regeneration process was investigated, revealing minimal P desorption (less than 8%) from Ca or Fe-loaded biomass, indicating the strong stability of the biomass-cation-P system. The estimated cost ranged from 8 to 161 euros per tonne, with an additional 230 euros when considering the pruning costs inherent to the crop. These costs fall below the threshold (320 euros per tonne) for the economically viable P reuse at the farm level. Consequently, CPPW, when reduced to powder and loaded with ions, emerges as an affordable adsorbent with good removal performance, offering a promising avenue for direct utilization in agriculture as both soil conditioner and fertiliser.

Amination-modified lignin recovery of aqueous phosphate for use as binary slow-release fertilizer

To address the global phosphorus crisis and solve the problem of eutrophication in water bodies, the recovery of phosphate from wastewater for use as a slow-release fertilizer and to improve the slow-release performance of fertilizers is considered an effective way. In this study, amine-modified lignin (AL) was prepared from industrial alkali lignin (L) for phosphate recovery from water bodies, and then the recovered phosphorus-rich aminated lignin (AL-P) was used as a slow-release N and P fertilizer. Batch adsorption experiments showed that the adsorption process was consistent with the Pseudo-second-order kinetics and Langmuir model. In addition, ion competition and actual aqueous adsorption experiments showed that AL had good adsorption selectivity and removal capacity. The adsorption mechanism included electrostatic adsorption, ionic ligand exchange and cross-linked addition reaction. In the aqueous release experiments, the rate of nitrogen release was constant and the release of phosphorus followed a Fickian diffusion mechanism. Soil column leaching experiments showed that the release of N and P from AL-P in soil followed the Fickian diffusion mechanism. Therefore, AL recovery of aqueous phosphate for use as a binary slow-release fertilizer has great potential to improve the environment of water bodies, enhance nutrient utilization and address the global phosphorus crisis.

Hyperbranched polyethyleneimine-functionalised chitosan aerogel for highly efficient removal of melanoidins from wastewater

Melanoidins are hazardous dark-coloured substances contained in molasses-based distillery wastewater. Adsorption is an effective approach to eliminate melanoidins from wastewater. However, melanoidin adsorption capacities of available adsorbents are unsatisfactory, which seriously limits their practical application. A hyperbranched polyethyleneimine-functionalised chitosan aerogel (HPCA) was fabricated as an effective adsorbent for melanoidin scavenging. HPCA demonstrated superior melanoidin adsorption efficiency because of its high specific surface area, abundant amino functional groups, and high hydrophilicity. Melanoidin removal rate of HPCA was 94.95%, which remained at 91.45% after 5 cycles. Notably, using the Langmuir isothermal model, the maximum melanoidin adsorption capacity of HPCA was determined to be 868.36 mg/g, surpassing those of most of previously reported adsorbents. Toxicity experiments indicated that HPCA can be considered a safe adsorbent with excellent biocompatibility that hardly threatens aquatic organisms. The efficient melanoidin removal of HPCA was attributed to electrostatic attraction, H-bonding, and van der Waals force. However, the adsorption might be predominantly controlled by electrovalent interaction between protonated amino groups of HPCA and carboxyl/carboxylate groups of melanoidins. Two novel models, namely, external diffusion resistance-internal diffusion resistance mixed model and adsorption on active site model, were employed to describe the dynamic mass transfer characteristics of melanoidin adsorption by HPCA.

Phosphate adsorption improvement using a novel adsorbent by CaFe/LDH supported onto CO2 activated biochar

It is imperative to remove phosphate from the aquatic system. This nutrient in excess can cause environmental problems such as eutrophication. Therefore, aiming to enhance phosphate removal, this work presents a novel adsorbent developed from the construction of Ca²⁺/Fe³⁺ layer double hydroxides (CaFe/LDH) supported onto biochar physically activated with CO₂ [CaFe/biochar (CO₂)]. Pristine biochar was produced from the pyrolysis of Eucalyptus saligna sawdust, activated with CO₂, and then impregnated with CaFe/LDH. The CaFe/biochar (CO₂) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). The characterization confirmed a proper synthesis of the new adsorbent. Experiments were conducted in the form of batch adsorption. Results indicated that the optimum pH and adsorbent dosage were 2.15 and 0.92 g L^-1, respectively. Adsorption kinetics, isotherms, and thermodynamics were also evaluated. Adsorption kinetics and isotherms were better fitted by the pseudo n order and Freundlich models, respectively. Results also indicated a better adsorption capacity (99.55 mg·g^-1) at 55 °C. The thermodynamic indicators depicted that the adsorption process was favorable, spontaneous, and endothermic. Overall, CaFe/biochar (CO₂) could be potentially applied for the adsorptive removal of phosphate from an aqueous solution.

Phosphate ion removal from aqueous solution using snail shell dust: biosorption potential of waste shells of edible snails

The freshwater snails, Filopaludina bengalensis and Pila globosa are widely used for human consumption and as a feed in aquaculture in India and Bangladesh. The generation of shells as a waste product following meat extraction from the live snails incites their utilisation as a potential biomaterial. Shell dust was prepared from the dried shells of F. bengalensis (FSD) and P. globosa (PSD) and employed for phosphate adsorption from aqueous solutions. Batch adsorption experiments were performed to examine the effects of various experimental conditions, such as biosorbent dose, agitation speed, temperature, contact time, pH, initial concentration of phosphate ions, and presence of co-existing ions. SEM, EDS, ICP-OES, FTIR, and XRD results indicated that phosphate ions were adsorbed onto the surface of shell dust particles. The experimental data fitted with the Langmuir isotherm with a maximum adsorption capacity of 62.50 and 66.66 mg g^-1 for FSD and PSD. The pseudo-second order kinetic model was well fitted, indicating the chemical adsorption process, and the thermodynamic parameters indicated that the adsorption mechanism of phosphate was spontaneous, feasible, and endothermic. Therefore, the results have established the potentiality of the waste shells of edible snails to be used as an eco-friendly and low-cost biosorbent for phosphate removal from wastewater.

An in situ grown amorphous ZrO2 layer on zeolite for enhanced phosphate adsorption

Zeolite supported amorphous metal oxide nanolayers with high specific surface area, abundant adsorption sites, and excellent reusability hold a bright prospect in the efficient removal of contaminants, yet it is proven to be still challenging to precisely regulate and control their synthesis. Herein, we reported a facile synthetic strategy for rational design and achieving the uniform and firm in situ growth of an amorphous ZrO2 layer decorated on the surface of zeolite (ZEO@AZ) for enhanced phosphate adsorption. The Langmuir isotherm model and pseudo-second order kinetic equation well described the adsorption process towards phosphate solution, and the synthetized ZEO@AZ exhibited an excellent maximum adsorption amount of 24.98 mgP g-1. Furthermore, the adsorption of phosphates on ZEO@AZ was confirmed to be chemisorption, endothermic and spontaneous. This approach for fabricating amorphous metal oxide nanolayers on a robust matrix may provide a new route for constructing composites with superb phosphate adsorption performance.

Phosphate adsorption characteristics of La(OH)3-modified, canna-derived biochar

La(OH)₃-modified canna biochar (CBC-La) was prepared by a coprecipitation method (dipping method), and its phosphate adsorption characteristics were investigated. The results show that the pseudo-second-order kinetics and the Langmuir model can be used to describe the adsorption process with a high level of accuracy. Adsorption equilibrium could be reached at 8 h, at which point the maximum adsorption capacity was shown to be 37.37 mg/g. CBC-La has excellent phosphate adsorption capacity in the middle to low concentrations (≤50 mg/L), and its removal rate can exceed 99 %. CBC-La also has wide pH adaptability (3-9) and a strongly selective adsorption performance. Notably, it can still maintain a removal rate of over 99.8 % in the presence of certain anions (NO₃^-, HCO₃^-, and CO₃^2-), and the presence of NH₄⁺ has a synergistic effect on the adsorption process. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the main mechanisms of CBC-La phosphate adsorption are electrostatic adsorption, ion exchange, ligand exchange and inner sphere complexation.

Comparative research on selective adsorption of Pb(II) by biosorbents prepared by two kinds of modifying waste biomass: Highly-efficient performance, application and mechanism

In this study, we used xanthate to modify two waste biomass materials (corn cob and chestnut shell) and prepared them as biosorbents in one step for effectively removing Pb(II) from aqueous solutions containing only Pb(II) or Pb(II), Cu(II) and Cd(II). The two biosorbents were characterized by SEM, EDS, FTIR and Zeta potential analysis, and the results of the characterization were used to explore the adsorption mechanism of Pb(II) on biosorbents. We compare the Pb(II) removal ability of the two biosorbents and the investigated factors that affect Pb(II) removal. The results show that the adsorption capacity of xanthate modified corn cob (X-CC) and xanthate modified chestnut shell (X-CS) for Pb(II) is related to pH, reaction time, temperature and initial concentrations of both adsorbent and adsorbate. The adsorption of Pb(II) on X-CC and X-CS follows Langmuir isotherm equation and quasi-secondary kinetic equation, and their fitted q_m values are 166.39 and 124.84 mg g^-1, respectively. The analysis shows that the biosorbent has high selectivity to Pb(II) rather than Cu(II) and Cd(II), and still maintains a high removal rate of Pb(II) in actual wastewater. The biosorbents remove metal ions mainly through ion exchange reaction and the functional group in the material complexes with the metal to form micro-precipitation. The high adsorption capacity in aqueous solution and low costs in the manufacturing process of the present biosorbents ensure that they have great potential in practical applications for treating heavy-metal contaminated surface water.

Preparation of TiO2/cellulose nanocomposites as antibacterial bio-adsorbents for effective phosphate removal from aqueous medium

The design of environmentally benign bio-adsorbents for the removal of phosphate from aqueous medium was an economic and effective way for controlling eutrophication. Herein, we prepared three kinds of TiO₂/cellulose (CE-Ti) nanocomposites by a facile hydrolysis-precipitation method, and used them as antibacterial bio-adsorbents for the removal of phosphate from aqueous medium. Multiple techniques including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and thermogravimetric analysis (TGA) were employed to characterize the nanostructure and characteristics of the prepared CE-Ti nanocomposite. The adsorption capacity of the CE-Ti was 19.57 mg P g^-1 according to the Langmuir model, which was 6 times higher than that of CE. Importantly, the bacterial inhibition zone of the CE-Ti was 2.88 mm (that of CE was 0 mm), indicating that CE-Ti had good antibacterial activity that could reduce the attachment of the microorganism to the surface of CE-Ti, which was suitable for long-term phosphate removal. Moreover, the CE-Ti had good adsorption selectivity and anti-interference capability, according to interfering ions and ion strength experiments. Furthermore, Ti⁴⁺ leakage tests suggested that CE-Ti was highly stable under acidic, neutral and alkali conditions. These results indicated that the CE-Ti nanocomposite could be utilized as a promising antibacterial bio-adsorbent for effective phosphate removal from aqueous medium.

Selenium in wastewater can be adsorbed by modified natural zeolite and reused in vegetable growth

Modified natural zeolites (MNZ) are widely used in pollutant removal, but how to address these MNZ that have adsorbed pollutants must be considered. Selenium is an essential trace element for metabolism and is also a water pollutant. Selenium is adsorbed in the water by MNZ in this study first. Then the Brassica chinensis L. was planted in the soil which contains the MNZ loaded with selenium (MNZ-Se) to explore selenium uptake. MNZ-Se release tests in water and soil were also considered. The results showed the following: (1) The maximum adsorption capacity of MNZ for selenium is 46.90 mg/g. (2) Water release experiments of MNZ-Se showed that regardless of how the pH of the aqueous solution changes, the trend of the release of selenium from MNZ-Se in aqueous solution is not affected and first decreases before stabilizing. (3) Soil release experiments of MNZ-Se showed that the selenium content in the soil increased and reached the concentration in the standard of selenium-rich soil. Addition amount and soil pH value will affect the release ratio. The release ratio of MNZ-Se in the water was higher than that in the soil. (4) With an increase in the soil MNZ-Se content, the selenium content in the soil and B. c increases. Above all, MZN can be a good medium for water pollutant removal and soil improvement.

Radiation grafting of dimethylaminoethyl methacrylate on cotton linter and subsequent quaternization as new eco-friendly adsorbent for phosphate removal

Quaternary ammonium salt type cotton linter (QCL) was synthesized by radiation grafting of dimethylaminoethyl methacrylate (DMAEMA) onto cotton linter and subsequent quaternization. Batch and column adsorption experiments were used to evaluate the adsorption behaviors of the QCL for phosphate. The adsorption kinetics of QCL for phosphate were well obeyed pseudo-second-order mode. The adsorption isotherms were well fitted by Langmuir, Temkin, and Dubinin-Radushkevich model. Column experiments showed that the breakthrough curves were dependent on the inlet concentration and flow rate but independent on space velocity. Moreover the QCL can be effectively regenerated for further repeated use at least 10 cycles. And QCL exhibited good selective adsorption for phosphate. Such high adsorption and desorption efficiency of QCL made it employing for phosphate adsorption in practical application.

Phosphorus removal from aqueous solution using modified walnut and almond wooden shell and recycling as soil amendment

Modified walnut wooden shell (MWWS) and almond wooden shell (MAWS) as novel anion exchangers were used to remove phosphorus (P) from aqueous solution. The raw and modified agricultural wastes were characterized using total N, total P, FT-IR spectra, SEM, BET, and EXD analysis. The effect of different parameters such as pH (4 to 8), contact time (5 to 600 min), and adsorbent dosage (1 to 8 g L^-1) on P adsorption was investigated. Adsorption of P onto MWWS and MAWS was studied using the batch technique with different concentration of P (5 to 200 mg L^-1) at 25 ± 2 °C. The P adsorption isotherms were fitted with the Freundlich and Langmuir equations. The k and n values were 1.57 mg g^-1 and 1.88 for MWWS and 1.91 mg g^-1 and 2.24 for MAWS, respectively. The maximum P adsorption capacities for MWWS and MAWS were 22.73 and 14.71 mg g^-1, respectively. The desorption-regeneration experimental results indicated about 4% and 3% reductions in MWWS and MAWS P adsorption efficiency after four consecutive regeneration cycles, respectively. The data well fitted with Pseudo-second-order kinetic model (R² ≥ 0.99), indicating that chemical interactions dominate the P adsorption process. Incubation studies showed the rate of P release in treated soil with P-loaded modified biosorbents was higher than control. Therefore, the MWWS and MAWS can potentially be used as an excellent adsorbent in remediation of contaminated waters by P and then recycled to soil.

Adsorptive removal of phosphate by the bimetallic hydroxide nanocomposites embedded in pomegranate peel

This study aimed to fabricate new and effective material for the efficiency of phosphate adsorption. Two types of adsorbent materials, the zirconium hydroxides embedded in pomegranate peel (Zr/Peel) and zirconium-lanthanum hydroxides embedded in pomegranate peel (Zr-La/Peel) were developed. Scanning electronic microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) were evaluated to give insight into the physicochemical properties of these adsorbents. Zr-La/Peel exceeded the adsorption efficiency of Zr/Peel adsorbents in batch adsorption experiments at the same pH level. The peel as a host can strive to have a strong "shielding effect" to increase the steadiness of the entrenched Zr and La elements. La and Zr are hydroxide metals that emit many hydrogen ions during the hydrolysis reaction, which contribute to protonation and electrostatic attraction. The highest adsorption capacity of La-Zr/Peel for phosphate was calculated to be 40.21 mg/g, and pseudo second-order equation is very well fitted for kinetic adsorption. Phosphate adsorption efficiency was reduced by an increase of pH. With the background of coexisting Cl^-, little effect on adsorption efficiency was observed, while adsorption capacities were reduced by almost 20-30% with the coexistence of [Formula: see text] , [Formula: see text] and humic acid (HA).

Adsorption of low concentrations of bromide ions from water by cellulose-based beads modified with TEMPO-mediated oxidation and Fe(III) complexation

Due to strong activity, it is very difficult to remove low concentrations of bromide in medical wastewater by traditional method, thus highly effective and greener adsorbents should be utilized to design. In this work, the cellulose beads (CBs) were modified by the TEMPO-mediated oxidation and then bonded with Fe³⁺ to fabricate Fe(III)-complexed carboxylated cellulose beads (Fe-CCBs) adsorbents. Structure and properties of Fe-CCBs were analyzed using Energy dispersive spectrum (EDS), Scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), total acidity and basicity groups, X-ray diffraction (XRD), N₂ adsorption-desorption and Thermogravimetric (TGA). Moreover, batch adsorption experiments showed that the adsorption of Br^- was better consistent with general-order kinetic model and Liu isotherm model, which could also further clarify the adsorption process mechanism. Meanwhile, the results revealed that removal of Br- was a spontaneous exothermic process and was more suitable to be carried out under neutral or acidic conditions. Furthermore, the mechanism of adsorption behavior of bromide ions on Fe-CCBs was based on a combination of electrostatic attraction and outer-sphere complexation. The results of this study can provide guidance for the design of novel material adsorbents and the removal of harmful anions from aqueous solutions.

Cellulose based materials for controlled release formulations of agrochemicals: A review of modifications and applications

Controlled release formulations (CRFs) of agrochemicals have been attracted considerable attention due to their friendliness to environment. The commercial supporting materials for CRFs of agrochemicals are non-degradable, leading to secondary pollution issue. Cellulose, as the most abundant natural materials in the world, is regarded as one of the most ideal substitutes for non-degradable supporting materials thanks to its good biocompatibility and biodegradability. As raw cellulose materials suffer several problems, such as poor mechanical strength, fast release rate, etc., chemical modifications are commonly performed to improve their properties. In this review, modification methods of cellulose materials for CRFs of agrochemicals were introduced. The relationships between release rate and cellulose based materials were discussed in detail. The applications of cellulose materials for CRFs of agrochemicals were also expounded.

Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 1. Microscopic Structure, Water Absorbency, and Degradation Performance

Few studies have been conducted on the use of general nanotechnology-based principles for providing nutrients to crops. Water and fertilizer are the most important inputs in determining crop yield and profit. In this paper, super-absorbent polymers SAP_WS (grafting wheat straw (WS) to poly(acrylic-co-acrylamide), which is WS-g-P(AA-co-AM)) and SAP_HEC (HEC (hydroxyethyl cellulose)-g-P(AA-co-AM)) and their semi-interpenetrating polymer network (semi-IPN) nanocomposites SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC (formed by chemical bonding of SAP_WS or SAP_HEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared. Due to the differences between activity and number of functional groups in WS and HEC, the water absorption properties and degradation performances of SAP_WS and SAP_HEC and their chemically bonded function nanocomposites SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC are different. The maximum water absorption ratios of SAP_WS, SAP_HEC, SI-PSRF/SAP_WS, and SI-PSRF/SAP_HEC can reach 200.00 g/g, 240.00 g/g, 119.91g/g, and 127.43 g/g, respectively. Effects of the structures of these four materials on their degradation performances were studied via a tomato pot experiment. The changes in microstructures of these materials during the degradation processes were characterized by TEM, SEM, FTIR, XRD, XPS, and other techniques. Results show that the degradation rate of the chemically bonded functional nanocomposites with a semi-IPN structure SI-PSRF/SAP system is higher than that of SAP+PSRF (the simple physically mixed system of PSRF and SAP). Due to the differences among the activities and quantities of functional groups in WS and HEC, the water absorption properties of SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC are different, and there are different degradation rates for these two functional nanocomposites.

Removal of Organic Micropollutants by Grainy Bentonite-Activated Carbon Adsorbent in a Fixed Bed Column

Organic micropollutants enter effluent streams and then flow into receiving waters. The volume adversely affects aquatic biota substantially. Therefore, many efforts have been made to develop methods for their elimination. The aim of this study was the removal of organic micropollutants with different properties from WWTP (wastewater treatment plant) effluent in fixed bed columns packed with several combinations of sand, granular activated carbon (GAC), and granular clay-carbonaceous composite. Two types of bentonite-powder activated carbon-based granules (Ben-AC) were prepared within this work, with different calcination temperature. It was found that higher calcination temperature enhanced the surface porosity and adsorption potential versus studied micropollutants due to dihydroxylation resulting in higher chemical activity. Introduction of these granules in the place of GAC in a fixed bed column enhances the removal degree of micropollutants and typical water quality parameters. For example, the reduction degree of color, phosphate, and nitrate concentrations increased from 83%, 69%, and 4% to 95%, 83%, and 24% for column I and II, respectively. The concentration of carbamazepine, octylphenol, nononylphenol, and anthracene was reduced by 75%, 83%, 72%, 99% in column I, while using column II or III their removal was: 86%, 97%, 99%, 99%, respectively. Independent of the column filling, the removal of carbamazepine was the lowest (75–86%), while the highest retention was obtained for anthracene (99%). The study of column performance in the treatment of effluent in time showed that column filled with Ben-AC-400 guaranteed high removal degree in the operating time. The batch adsorption data were better described by both the Langmuir model.

A biodegradable Fe-fertilizer with high mechanical property and sustainable release for potential agriculture and horticulture applications

A low-cost and biodegradable Fe-fertilizer bead with sustained release behaviors and excellent mechanical strength for potential agriculture applications.

Comparative analysis on adsorption properties and mechanisms of nitrate and phosphate by modified corn stalks

We compare and analyze the different properties and mechanisms of MCS on nitrate and phosphate.