Potassium Adsorption Research Articles

Oxygen-containing groups assist in enhancing Li+/K+ storage: Balancing adsorption and intercalation mechanisms

Porous carbon nanosheets were prepared using a high-temperature solid-phase method and subsequently modified through oxidative acid treatment to introduce oxygen-containing groups. The application and performance of these nanosheets as anodes in lithium-ion and potassium-ion batteries were investigated. The results indicated that the oxidative acid treatment successfully enhanced the porous carbon nanosheets' capacity for storing Li+/K+. Electrochemical analysis revealed that the oxygen-containing groups balanced intercalation and surface storage behaviors, optimizing the nanosheets' storage performance. These modified porous carbon nanosheets (termed SN@PCNs) demonstrated significantly boosted reversible Li+ and K+ storage capacities, achieving 1038.1 mAh⋅g−1 and 371.7 mAh⋅g−1 at 0.1 A g−1, respectively, while maintaining capacities of 443.3 mAh⋅g−1 for Li+ and 153.9 mAh⋅g−1 for K+ at 5.0 A g−1. Furthermore, the study emphasized the significance of a balanced surface capacitance and solid-phase diffusion storage mechanism in attaining high storage capacity and cycle stability. Moderate oxidation and the introduction of oxygen-containing groups were identified as crucial factors in optimizing performance. Additionally, potassium adsorption storage exhibited an advantage over lithium adsorption storage, and the impact of oxygen-containing groups on potassium storage performance was even more pronounced.

Free-standing cubic gauche nitrogen stable at 760 K under ambient pressure.

Cubic gauche nitrogen (cg-N) has received wide attention for its exceptionally high energy density and environmental friendliness. However, traditional synthesis methods for cg-N predominantly rely on high-pressure techniques or the utilization of nanoconfined effects using highly toxic and sensitive sodium azide as precursor, which substantially restrict its practical application. On the basis of the first-principles simulations, we found that adsorption of potassium on the cg-N surface exhibits superior stabilization compared to sodium. Then, we chose safer potassium azide as precursor for synthesizing cg-N. Through plasma-enhanced chemical vapor deposition treatment, the free-standing cg-N was successfully synthesized without the need for high-pressure and nanoconfined effects. It demonstrated excellent thermal stability up to 760 K, and then rapid and intense thermal decomposition occurred, exhibiting typical thermal decomposition behaviors of high-energy-density materials. The explosion parameters were also measured using laser-induced plasma spectroscopy. Our work has substantially promoted the practical application of cg-N as HEDMs.

The analysis of release and percolation rate of nutrients from regular and obsidian-based slow-release fertilizers.

Research on the observation of nutrient release rates from slow-release and regular fertilizers combined with the percolation rate in the soil is scarce. This work aims to observe potassium and phosphate release behavior from slow-release and regular fertilizer, followed by the percolation of that nutrient in the soil. The characteristics of the soil were analyzed using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscope (SEM). The concentration of potassium and phosphate in soil is analyzed using Atomic Absorption Spectroscopy (AAS) and Ultraviolet-Visible Spectroscopy (UV-Vis), respectively. The release rate of nutrients from slow-release fertilizer is 6 to 8 times slower than regular fertilizer. Meanwhile, the rate of nutrients released from slow-release and regular fertilizer followed by soil percolation matches the quadratic equation. Potassium adsorption on the soil surface is significantly higher than that of potassium. The negativity of soil polarity contributed to the high level of potassium adsorption on soil particle surfaces. The low phosphate adsorption capability of magnetite and the negativity of soil polarity contributed to the soil's low phosphate adsorption.

Quantum-Confined Lifshitz Transition on Weyl Semimetal Td-MoTe2.

Adsorption of alkali atoms onto material surfaces is widely utilized for controlling electronic properties and is particularly effective for two-dimensional materials. While tuning the chemical potential and band gap and creating quantum-confined states are well established for alkali adsorption on semiconductors, the effects on semimetallic systems remain largely elusive. Here, utilizing angle-resolved photoemission spectroscopy measurements and density functional theory calculations, we disclose the creation of two-dimensional electron gas and the quantum-confined Lifshitz transition at the surface of a Weyl semimetal Td-MoTe2 by potassium adsorption. Electrons from potassium adatoms are shown to be transferred mainly to the lowest unoccupied band within the gapped part of the Brillouin zone, which, in turn, induces strong surface band bending and quantum confinement in the topmost layer. The quantum-confined topmost layer evolves from a semimetal to a strong metal with a Lifshitz transition departing substantially from the bulk band. The present finding and its underlying mechanism can be exploited for the creation of electronic heterojunctions in van der Waals semimetals.

Artificial neural networks in soil quality prediction: Significance for sustainable tea cultivation

In today's era artificial intelligence is quite popular, one of the most effective algorithms used is Artificial Neural Networks (ANN). In this study, the determination of soil quality using the Soil Management Assessment Framework (SMAF) model in areas where tea cultivation is carried out at the micro-watershed scale and the predictability of soil quality using ANN were evaluated. According to the results, the soil quality indices of tea-growing areas were generally classified as “medium” between 55 and 70 %. Among the evaluated features for determining soil quality, the highest relative importance value was for soil organic carbon content (13 %) and potential mineralizable nitrogen (13 %), whereas the lowest values were for exchangeable potassium (4 %) and sodium adsorption ratio (SAR) (4 %). In addition, when comparing the actual and predicted values for soil quality prediction using ANN, the Lin's concordance correlation coefficient (LCCC), ratio of performance to deviation (RPD), and R2 values were found to be 0.93, 2.95, and 0.89, respectively. Significant properties for the determined values within a 90 % predicted interval were found to be organic matter, microbial biomass carbon, bulk density, and aggregate stability of the soils. Moreover, the uncertainty values (standard deviation) in the model predictions were determined to be within the range of 1.01–4.56 %. Consequently, the Soil Quality Index (SQI) obtained from the SMAF model using 12 soil properties in tea-growing areas could be accurately predicted using ANN. As a result of this study, digital maps showing the spatial distribution of SQI and the predicted uncertainties can help monitor SQI levels in this area.

Ultrastable Organic Anode Enabled by Electrochemically Active MXene Binder toward Advanced Potassium Ion Storage.

Conjugated carbonyl compounds are regarded as promising organic anode materials for potassium ion batteries (PIBs) due to their rich redox sites, excellent reversibility, and structural tunability, but their low electrical conductivity and severe solubility in organic electrolytes have substantially restricted their practical application. Herein, 2D MXene is utilized as an electrochemically active binder to fabricate perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) electrodes for high-performance PIBs. MXene, coupled with Super-P particles, served as a binder and conductive matrix to facilitate rapid ion and electron transport, restrain the solubility of PTCDA, promote potassium adsorption, and alleviate the volume expansion of PTCDA during potassiation. Consequently, the PTCDA electrode bonded by the MXene/Super-P system delivers excellent potassium storage performance in terms of a high capacity of 462 mAh g-1 at 50 mA g-1, superior rate capability of 116.3 mAh g-1 at 2000 mA g-1, and stable cycle performance over 3000 cycles with a low capacity decay rate of ∼0.0033% per cycle. When configured with the PTCDA@450 cathode, an all-PTCDA potassium ion full cell delivers a maximum energy density of 179.5 Wh kg-1, indicating the superiority of MXene as an electrochemically active binder to promote the practical application of organic anodes for PIBs.

Exploring diclofenac potassium adsorption on activated carbon: A comprehensive statistical physics and experimental approach

This study aims to contribute to understanding the removal processes of diclofenac potassium (DP) medicine in wastewater treatment systems, employing activated carbon (AC) as an adsorbent. To achieve this goal, a multidisciplinary approach was adopted, integrating experimental and theoretical analyses of equilibrium data regarding the adsorption of DP on AC. Five statistical physics models were applied to determine the model best for the adsorption process. The selection of the most appropriate model considered both the performance of the models and the analysis of the estimated parameters. Statistically, all models exhibited satisfactory results. However, when analyzing the estimated parameters, the double-layer model with single adsorption energy emerged as the most suitable model to describe the analyzed process. Based on the chosen model’s parameters, we observed that as the temperature increases, the number of active sites occupied during adsorption and their availability on the adsorbent also increases. However, the number of available adsorption sites decreases as the temperature rises. The half-saturation concentration, in turn, increases with increasing temperature, suggesting that the process is favored when temperatures above room temperature are used. Additionally, higher temperatures provide better removal results, indicating that DP molecules’ non-parallel and parallel orientations on the AC surface favor the adsorption process. Finally, our combined results led to the proposal of a mechanism for DP adsorption on AC, which is based on physical adsorption interactions between adsorbate-adsorbent and adsorbate–adsorbate.

Twin graphene as an anode material for potassium‐ion battery: A first principle study

AbstractUsing density functional theory, we have investigated the usage of twin graphene as an anode material for potassium‐ion batteries (KIBs). Twin graphene demonstrates excellent structural and cycling stability, with minimal changes in lattice parameters and negative cohesive energy during K charge/discharge cycles. Notably, the host material (twin graphene) offers multiple stable adsorption sites for potassium ions. We even observed that the pristine twin graphene, which is a semiconductor, consequently becomes metallic upon potassium adsorption. Twin graphene provides a high theoretical capacity of 495.84 mAh/g, along with low diffusion barrier of 0.290 V for K diffusion. Furthermore, the high electrical conductivity and low open‐circuit voltage of the chosen host will definitely enhance its performance as a KIB material. The structural integrity of twin graphene is also retained with the adsorption of potassium ion, as checked through ab initio molecular dynamics simulation. These findings suggest that twin graphene may be considered as a promising anode material for KIBs.

Tunable Interfacial Electric Field‐Mediated Cobalt‐Doped FeSe/Fe3Se4 Heterostructure for High‐Efficiency Potassium Storage

AbstractThe interfacial electric field (IEF) in the heterostructure can accelerate electron transport and ion migration, thereby enhancing the electrochemical performance of potassium‐ion batteries (PIBs). Nevertheless, the quantification and modulation of the IEF for high‐efficiency PIB anodes currently remains a blank slate. Herein, we achieve for the first time the quantification and tuning of IEF via amorphous carbon‐coated undifferentiated cobalt‐doped FeSe/Fe3Se4 heterostructure (denoted UN‐CoFe4Se5/C) for efficient potassium storage. Co doping can increase the IEF in FeSe/Fe3Se4, thereby improving the electron transport, promoting the potassium adsorption capacity, and lowering the diffusion barrier. As expected, the IEF magnitude in UN‐CoFe4Se5/C is experimentally quantified as 62.84 mV, which is 3.65 times larger than that of amorphous carbon‐coated FeSe/Fe3Se4 heterostructure (Fe4Se5/C). Benefiting from the strong IEF, UN‐CoFe4Se5/C as a PIB anode exhibits superior rate capability (145.8 mAh g−1 at 10.0 A g−1) and long cycle lifespan (capacity retention of 95.1 % over 3000 cycles at 1.0 A g−1). Furthermore, this undifferentiated doping strategy can universally regulate the IEF magnitude in CoSe2/Co9Se8 and FeS2/Fe7S8 heterostructures. This work can provide fundamental insights into the design of advanced PIB electrodes.

Tunable Interfacial Electric Field-Mediated Cobalt-Doped FeSe/Fe3Se4 Heterostructure for High-Efficiency Potassium Storage.

The interfacial electric field (IEF) in the heterostructure can accelerate electron transport and ion migration, thereby enhancing the electrochemical performance of potassium-ion batteries (PIBs). Nevertheless, the quantification and modulation of the IEF for high-efficiency PIB anodes currently remains a blank slate. Herein, we achieve for the first time the quantification and tuning of IEF via amorphous carbon-coated undifferentiated cobalt-doped FeSe/Fe3Se4 heterostructure (denoted UN-CoFe4Se5/C) for efficient potassium storage. Co doping can increase the IEF in FeSe/Fe3Se4, thereby improving the electron transport, promoting the potassium adsorption capacity, and lowering the diffusion barrier. As expected, the IEF magnitude in UN-CoFe4Se5/C is experimentally quantified as 62.84 mV, which is 3.65 times larger than that of amorphous carbon-coated FeSe/Fe3Se4 heterostructure (Fe4Se5/C). Benefiting from the strong IEF, UN-CoFe4Se5/C as a PIB anode exhibits superior rate capability (145.8 mAh g-1 at 10.0 A g-1) and long cycle lifespan (capacity retention of 95.1 % over 3000 cycles at 1.0 A g-1). Furthermore, this undifferentiated doping strategy can universally regulate the IEF magnitude in CoSe2/Co9Se8 and FeS2/Fe7S8 heterostructures. This work can provide fundamental insights into the design of advanced PIB electrodes.

Potassium adsorption capacity and desorption kinetics in soils of Qenberenaweti sub-watershed, central highlands of Ethiopia

Determining the supply and uptake of K nutrient and the dynamic equilibrium (adsorption-desorption) reactions among the K forms in the soils are not commonly addressed in the highlands of Ethiopia. A study was therefore initiated to determine the adsorption capacity of the exchangeable K and the release kinetics of the non-exchangeable K in the soils of the Qenberenaweti Sub-watershed. Twelve disturbed surface (0–20 cm) soil sub-samples were collected from every farmland which was representative of each pre-identified soil type (Vertic Cambisols, Pellic Vertisols, Pisoplinthic Luvisols, Relictistagnic Cambisols, Pisoplinthic Cambisols, and Plinthofractic Cambisols). A composite sample was made in duplicate for the determination of K adsorption capacity and desorption kinetics per soil type. The mean maximum (69.47 ± 4.31 %) and minimum (56.16 ± 6.04 %) K adsorption rates were obtained from the Plinthofractic Cambisols and Vertic Cambisols, respectively. Among the tested isotherm models, the goodness of the Freundlich was better fit the data of all experimental soils; hence, a modified equation of this model (qe = aCeb/a) could be used to describe the theoretical doses of K fertilizers required to develop K levels in soil solutions. The highest constant K releases from the Plinthofractic Cambisols (47 mg kg−1), Pisiopllintic Cambisols (46 mg kg−1), and Pisoplinthic Luvisols (44 mg kg−1) were attained at the 9th extraction. In comparison, it was noticed at the 7th and 11th extractions of the Relictistagnic Cambisols (45 mg kg−1) and both Pellic Vertisols (48 mg kg−1) and Vertic Cambisols (42 mg kg−1), respectively. The equation of power function was the best to successfully describe the released K+ from all the experimental soils. Eventually, determining the adsorption capacity and release kinetics of K at a site-specific level helps to know the relative potential of the soils to supply K and also plan for an effective K fertilization strategy.

A Study of potassium adsorption in some soils north of Dhi-Qar province in Iraq

To study the phenomenon of potassium adsorption to some soils in northern Dhi-Qar Governorate / southern Iraq with different characteristics, which included agricultural and non-agricultural sites such as Al-Shatrah, Al-Nasr, Al-Dawaya, Al-Rifai, Qalat Sukar, and Al-Fajr, 1 g of soil was taken and potassium was added to it at levels (0, 20, 40, 60, 80). 100, 120, 140) mg L−1, prepared from potassium chloride KCl, and complete the volume to 50 ml with a solution of 0.01 M CaCl2. The concepts of thermal symmetry of adsorption equations were tested (Langmuir, Freundlich). The results of the study showed that the adsorption equations succeeded in describing the adsorption of potassium by soil samples, but these equations differed in their efficiency depending on the soil properties of agricultural and non-agricultural sites. The Langmuir equation was the most efficient in describing the adsorption of potassium by soil samples of non-agricultural sites because it obtained the highest values of the coefficient of determination R2 compared to the Freundlich equation. The results of the study also showed that the amount of potassium absorbed by the soil increased with the increase in the amount of potassium added to the balance solution, and the amount absorbed differed according to the characteristics of the soil and the sites studied. The values of the diffusion coefficient (Kd) decreased with an increase in the concentration of potassium added to the soil, and its value increased in the soil of non-agricultural sites compared to agricultural sites, where the value of (Kd) for the soil of non-agricultural sites ranged between (2.60 - 11.75) L kg−1 and for agricultural sites between (2.70-11.25) L kg−1.

Boosting Potassium Adsorption and Diffusion Performance of Carbon Anodes for Potassium-Ion Batteries via Topology and Curvature Engineering: From KT-Graphene to KT-CNTs.

We propose a two-dimensional carbon allotrope (named KT-graphene) by incorporating kagome and tetragonal lattices consisting of trigonal, quadrilateral, octagonal, and dodecagonal rings. The introduction of non-hexagonal rings can give rise to the localized electronic states that improve the chemical reactivity toward potassium, making KT-graphene a high-performance anode material for potassium-ion batteries. It shows a high theoretical capacity (892 mAh g-1), a low diffusion barrier (0.33 eV), and a low average open-circuit voltage (0.51 V). The presence of electrolyte solvents is propitious to boost the K-ion adsorption and diffusion capabilities. Moreover, one-dimensional nanotubes (KT-CNTs), rolled up by the KT-graphene sheet, are metallic regardless of the tube diameter. As the curvature increases, KT-CNTs exhibit significantly increased surface activity, which can promote the electron-donating ability of K. Furthermore, the curvature effect greatly enhances the efficiency of K diffusion on the inner surface compared to that on the outer surface.

Encapsulating Bi Nanoparticles in Reduced Graphene Oxide with Strong Interfacial Bonding toward Advanced Potassium Storage.

Bismuth (Bi) is regarded as a promising anode material for potassium ion batteries (PIBs) due to its high theoretical capacity, but the huge volume expansion during potassiation and intrinsic low conductivity cause poor cycle stability and rate capability. Herein, a unique Bi nanoparticles/reduced graphene oxide (rGO) composite is fabricated by anchoring the Bi nanoparticles over the rGO substrate through a ball-milling and thermal reduction process. As depicted by the in-depth XPS analysis, strong interfacial Bi-C bonding can be formed between Bi and rGO, which is beneficial for alleviating the huge volume expansion of Bi during potassiation, restraining the aggregation of Bi nanoparticles and promoting the interfacial charge transfer. Theoretical calculation reveals the positive effect of rGO to enhance the potassium adsorption capability and interfacial electron transfer as well as reduce the diffusion energy barrier in the Bi/rGO composite. Thereby, the Bi/rGO composite exhibits excellent potassium storage performances in terms of high capacity (384.8 mAh g-1 at 50mA g-1), excellent cycling stability (197.7 mAh g-1 after 1000 cycles at 500mA g-1 with no capacity decay) and superior rate capability (55.6 mAh g-1 at 2 A g-1), demonstrating its great potential as an anode material for PIBs.

Geopolymer Foam Reinforced with Iron Ore Flotation Tailing for Potassium Adsorption and Controlled Release in Water

Geopolymer Foam Reinforced with Iron Ore Flotation Tailing for Potassium Adsorption and Controlled Release in Water

Observation of a Folded Dirac Cone in Heavily Doped Graphene.

Superlattice potentials imposed on graphene can alter its Dirac states, enabling the realization of various quantum phases. We report the experimental observation of a replica Dirac cone at the Brillouin zone center induced by a superlattice in heavily doped graphene with Gd intercalation using angle-resolved photoemission spectroscopy (ARPES). The replica Dirac cone arises from the (√3× √3)R30° superlattice formed by the intervalley coupling of two nonequivalent valleys (e.g., the Kekulé-like distortion phase), accompanied by a bandgap opening. According to the findings, the replica Dirac band in Gd-intercalated graphene disappears beyond a critical temperature of 30 K and can be suppressed by potassium adsorption. The modulation of the replica Dirac band is primarily attributable to the residual frozen gas, which can act as a source of intervalley scattering at temperatures below 30 K. Our results highlight the persistence of the hidden Kekulé-like phase within the heavily doped graphene, enriching our current understanding of its replica Dirac Fermions.

Soil potassium adsorption at several shallot center areas, Brebes Regency, Central Java Province

Brebes Regency, Central Java, is one of Indonesia's most important shallot production center implementing intensive agriculture. In the bulb production, K is needed more than other nutrients. This study aimed to assess and describe the adsorption characteristics of K on the soils of the shallot farming system in Brebes District, Central Java. Soil samples were collected at several locations in the shallot center areas of Brebes Regency, Central Java Province. The observed soil properties included pH H<sub>2</sub>O, EC, soil texture, organic C, potential-K, exchangeable Ca, Mg, Na, and K, CEC, exchangeable Al and H, and water-soluble K. K adsorption was simulated by the Freundlich equation. The proportion of K from low to high of retention energy in the soil studied had the order, namely water-soluble K<exchangeable K<potential-K. The K adsorption result showed that the soil had a high capacity to adsorb K. It indicated that added K was accumulated in the soil. The high capacity to adsorb K indicated that K accumulated in Brebes with continuous K fertilization. This research recommended that to increase the efficiency of K fertilizer, it is necessary to introduce the technology to mine K in Brebes soils like bacteria capable of dissolving K or biofertilizers.

Colorado River (Argentina) Water Crisis Scenarios and Influence on Irrigation Water Quality Conditions

The characterization and evaluation of water quality in the Valle Bonaerense del Río Colorado (VBRC), Buenos Aires, Argentina, is necessary, given the immense importance of this region for sustaining the population livelihoods and maintaining the ecological balance, especially in the face of drought and climate change scenarios, and loss of crop production yields. This study evaluated the possible reuse of drainage canals from the perspective of their use for irrigation. Surface water samples were collected at four sampling sites during 2015–2021, one over the Colorado river entering the VBRC, and the remaining three drainage canals flow into the Atlantic Ocean. These physicochemical parameters were performed following the protocols proposed using standard methods: total dissolved solids, pH, electrical conductivity (EC), calcium, magnesium, sodium, potassium, carbonates, bicarbonates, chlorides, sulfates and sodium adsorption ratio were analyzed and classified. The irrigation water quality index (IWQI), principal component analysis, hierarchy of classes analysis and statistical analysis were applied to the dataset. The general hydrochemistry of the VBRC river water indicates a slightly alkaline nature, with a mean pH value of 8.03, and the predominance order of the major ions follows the pattern of Na+ > Ca2+ > Mg2+ > K+, and SO42− > Cl− > HCO3− + CO32− for the anions. For the IWQI, 88.06% of the samples analyzed were classified as safe water for irrigation, and a theoretical yield loss was estimated for crops considering the salinity variable, with vegetables showing the highest losses. The surface water from rivers increases the EC due to the decrease in its discharge because of the water crisis affecting Latin America. Water reuse could be useful for one of the three drainage canals. This study concludes that the reuse of drainage water (S2) has great potential as an adaptation strategy to address the water scarcity and climate change challenges in the Colorado river basin. The research highlights the importance of considering this alternative to achieve sustainable water management in the region. Moreover, the data obtained from the study can be used for making policy and resource management decisions. In view of the possible scenarios of low water flow and increases in the EC values, it is recommended to reorient agricultural production toward crops with higher tolerance to salinity as an alternative, to ensure the sustainability and viability of production in the basin.

Potassium adsorption on substrates formulated with vermiculite and peat

The substrates composition can take place from different raw materials, being an influencer of the water and nutrient retention capacity, an important dynamic in the management of the cultivation in containers due to the possibility of nutrient leaching. It was aimed to quantify the Potassium adsorption to substrates with different proportions of vermiculite and peat, in addition to determining adsorption isotherms which would best fit the observed adsorption data, for contact periods of one and seven days. We carried out batch adsorption essays, using as an adsorbent media substrate prepared with different proportion of vermiculate and peat, and as adsorbate, solutions with concentrations of 0, 25, 50, 75 and 100 mg/L of K. The substrate that showed the highest adsorption capacity, then less leaching potential, was the one constituted with the largest amount of peat. The Freündlich’s isotherm best represents the K adsorption phenomenon in all the studied treatments.

Fertirrigation with nanofiltration retentate from thermomechanical pulp mill effluents

The objective of the present study was to evaluate the potential for using the retentate from nanofiltration (NF) treatment of thermomechanical pulp (TMP) effluent for fertirrigation. Nanofiltration retentates from tertiary effluent treatment from a Brazilian TMP pulp mill were used. Electrical conductivity (EC) and the concentration of both metals (Mn2+, Mg2+, Fe2+, Ca2+, Na+, K+, Cu2+) and chlorides in the NF retentate were evaluated. The sodium (SAR) and potassium (PAR) adsorption ratios were calculated. The risks of increasing the salinity, effects on the infiltration rate, toxicity and excess nutrients were evaluated according to the American and European standards, and application according to crop and soil were analyzed according to the Brazilian standard. The NF retentate is classified as irrigation water Class I for the risks of reduced water infiltration into the soil, availability of nutrients and the concentration of copper and iron, Class II for the risks of toxicity, pH and concentration of manganese and Class III for the risks of salinity and concentrations of TS, TSS and turbidity, according to American and European standards. The salinity content and the physicochemical characteristics classify the effluent NF retentate, according to the Brazilian standard, as fresh water and Class III for irrigation. The NF retentate from thermomechanical pulp mill effluents, according to both the American and the European standards, cannot be used for fertirrigation, as it is classified as Class III. However, the Brazilian standard allows its use for the irrigation of any tree species, cereals and forages and as a source of nutrients to reduce fertilizer use. The retentate can be applied to highly salt-tolerant plant crops such as Eucalyptus globulus, Eucalyptus camaldulensis and sugarcane, and may be used in soil with a basic pH and high permeability.