Extractable Phosphorus Research Articles

Comparing laser-induced breakdown spectroscopy and visible near-infrared spectroscopy for predicting soil properties: A pan-European study

Soil organic carbon (SOC), texture, clay/organic carbon (OC) ratio, and extractable phosphorus are among the key soil descriptors representing the physical, chemical, and biological properties. However, analyzing these soil properties using conventional methods of analysis is time-consuming and often involves the use of hazardous chemicals. Therefore, scaling these methods to analyze more samples covering large geographical distributions within a reasonable turn-around time has become a challenge. In this study, two rapid techniques, namely laser-induced breakdown spectroscopy (LIBS) and visible and near-infrared spectroscopy (vis-NIRS), were compared for the prediction of SOC, texture, extractable phosphorus, and clay/OC ratio. A total of 896 samples collected from 23 European countries from the Land Use/Cover Area frame Survey (LUCAS) database were used to represent a wide distribution in terms of soil texture and geographical coverage. The data was manually split into calibration and validation samples while ensuring a representative geographical distribution in the calibration and validation set for the selected samples. Partial least square regression (PLSR) models were developed for both LIBS and vis-NIRS and compared based on prediction accuracy. LIBS outperformed vis-NIRS in predicting SOC, sand content, and clay/OC ratio, with root mean square error of prediction (RMSEP) values of 1.79 %, 12 %, and 7.69, respectively. Conversely, vis-NIRS yielded slightly higher RMSEP values for SOC, sand content, and clay/OC ratio predictions at 1.88 %, 15 %, and 8.13, respectively. Both LIBS and vis-NIRS performed similarly in predicting clay content, with an RMSEP of 6 %. However, there was a low predictive ability for silt and phosphorus concentration, as shown by the weak correlations (R2 < 0.5) between the predicted and reference soil properties. There was no significant difference between LIBS and vis-NIRS predictions for clay, silt, and SOC content (p > 0.05). However, there was a significant difference between the predicted sand content (p = 0.011) and clay/OC ratio (p < 0.001). The overall better performance of LIBS highlights its potential for application in a wide range of soils, especially for soils covering large geographical distributions and varying soil properties. Further, both techniques present opportunities for rapid determination of soil properties important for evaluating soil health on continental scales.

Selective recovery of high purity aluminium phosphate from incinerated sewage sludge ash with Zr-modified biochar

Phosphorus recovery from incinerated sewage sludge ash (ISSA) is critical for the sustainable development of phosphorus resources due to its non-renewable nature. An innovative strategy based on a Zr-modified rice-husk biochar (Zr-RB) adsorbent has been proposed for the selective recovery of high-purity AlPO4 products from ISSA. 0.1 mol/L H2SO4 was chosen to extract phosphorus from ISSA with a phosphorus extraction of 54.5 ± 1.6 mg/g. Phosphorus was selectively adsorbed by the Zr-RB adsorbent with a maximum adsorption capacity of 53.1 ± 0.6 mg/g according to the Langmuir isotherm model. The adsorption kinetics of phosphorus in the leachate followed the pseudo-second order model, suggesting phosphorus adsorption by chemisorption processes. After 5 phosphorus adsorption-desorption cycles, the Zr-RB adsorbent still showed good adsorption performance for phosphorus, indicating its high stability. Electrostatic attraction and ligand exchange on the Zr-RB adsorbent were mainly responsible for the adsorption of phosphorus from the leachate. The simulation and experimental results demonstrated the production of high-purity AlPO4 products at the pH = 3.0 without the addition of exogenous substances, indicating the application potential of recovering high-value AlPO4 products from ISSA based on the Zr-RB adsorbent.

Low alkaline vegetation concrete with silica fume and nano-fly ash composites to improve the planting properties and soil ecology

Abstract Slope protection and erosion management are severely hampered by the rapid infrastructure development in mountainous valleys, especially during the monsoon season. While conventional approaches like vegetation, porous concrete, and inorganic procedures have been used, stronger and more ecologically friendly alternatives are still needed. A new kind of concrete called vegetation concrete (VC) allows roots to grow through the concrete frame by combining plant integration with porous concrete. This creative method might be used for environmentally friendly building and planting. The alkalinity of VC significantly impacts its planting capabilities and soil nutrient levels, making it crucial to reduce VC alkalinity. In this study, silica fume (SF) and fly ash (FA) were combined to create low-alkaline VC. The effects of SF and FA on VC’s alkalinity, porosity, compressive strength, and planting characteristics were examined. The study also investigated VC’s influence on soil fertility and its impact on soil nutrients. Test results revealed that SF and FA reduced the pH of the VC by reducing calcium hydroxide (CH) crystals. While SF had a lower basicity coefficient (M) than FA, it had a more significant effect on lowering VC alkalinity. The compressive strength decreased with FA but increased with SF, despite SF having a smaller cement component in VC–SF mixes. This suggests that blending VC with SF and FA is feasible, with the SF dosage exceeding the FA dosage for reduced alkalinity and increased strength. Lowering VC alkalinity through SF and FA increased soil nutrients, including hydrolyzable nitrogen (AH-N), extractable phosphorus (P), and potassium (K). It also improved planting properties like root development, stem height, and leaf relative water content. Using VC for soil stabilization did not reduce soil fertility but instead increased the available phosphorus and alkali-hydrolyzable nitrogen in the soil by 32.81 and 52.92%, respectively. The findings of this study open up new avenues for investigation into this technology and have important ramifications for the use of VC technology, particularly in Indian contexts.

Farming systems and soil fertility management practices in smallholdings on the southern slopes of Mount Kilimanjaro, Tanzania

In the northern part of Tanzania, the slopes of Mount (Mt.) Kilimanjaro are the most important areas, both in terms of socio-economic development and ecological succession. The main agricultural systems in the area are banana-based (in the highlands) and maize-based (in the lowlands), with strong interlinkage between them via residual transfer from the lowlands to the mountains. This study assessed the soil fertility status between the two contrasting farming areas of highland and lowland farms in Hai district along the slopes of Mt. Kilimanjaro. To achieve this, smallholder farmers along the slope [from above 1000 meters above sea level (m.a.s.l) banana-based down to maize-based, i.e., less than 1000 m.a.s.l] who practice crop residual transfer from maize-based to banana-based farming systems were selected. Qualitative information regarding the demographics, farming practices, and soil fertility management in the two areas were gathered using a semi-structured questionnaire. Soils from both areas (highland and lowland farms) were collected and analyzed in the laboratory for the key soil properties. The demographic results show that agriculture is mostly done by adults and elders (&amp;gt;40 years old). Manure was most commonly reported to be used in the highlands, while inorganic fertilizers were mainly used in lowland areas. The major challenges for soil fertility management are a shortage of manure and high cost of inorganic fertilizers. The results of soil nutrients revealed that lowland zones (&amp;gt;1000 m.a.s.l) had significantly (p&amp;lt; 0.01) lower levels of nitrogen (0.14%) and organic carbon (OC) (1.22%) compared with highland zones. Extractable phosphorus (P) was significantly lower in both the highland and lowland zones, at 9.3 mg kg-1 and 8.2 mg kg-1, respectively, compared with other nutrients. However, potassium (K+) was significantly (p&amp;lt;0.01) lower [0.34 cmol (+) kg-1] in the highland zone compared to lowland areas. The data show that there is a severe depletion of soil nutrients in the lowland area of Hai district. Notwithstanding the efforts of the small-holder farmers; the study comes to the conclusion that increasing agricultural yield and the sustainability of farming systems require replenishing the nutrients in the soil along the slope of Mount Kilimanjaro.

Extraction of lithium and phosphorus from amblygonite using calcium sulfate roasting and water leaching

This work proposes the roasting of amblygonite with calcium sulfate followed by water leaching to extract lithium and phosphorus. Various roasting parameters including roasting temperature, the mass ratio CaSO4/ore, roasting time as well as leaching parameters, such as the liquid/solid ratio, temperature and time, have been carefully investigated. The lithium extraction efficiency can be as high as 99.8% with a mass ratio of CaSO4/ore of 0.85 after roasting at 775 °C for 1 h and water leaching at a liquid/solid ratio of 3 mL/g at 100 °C for 2 h. The XRD analysis demonstrates that the fluoride in the amblygonite can be converted into Ca5(PO4)3F and CaF2. Lithium in the leach liquor can be recovered as Li2CO3. Meanwhile, the phosphorus in the water leach residue can be recovered as FePO4 with a high recovery of 96.6% after acid dissolution and precipitation, which can be further treated to produce LiFePO4.

Hydrochloric Acid Catalyzed Hydrothermal Treatment to Recover Phosphorus from Municipal Sludge

Resource utilization of sludge is critical because traditional sludge treatment methods cause a large amount of nutrient loss. This study investigated the impact of hydrochloric acid quantity, reaction temperature, and time on phosphorus release and migration from municipal sludge during hydrothermal treatment and designed a sludge disposal method for the recovery and utilization of phosphorus resources. We know that hydrochloric acid destroys the complexation of calcium and phosphorus precipitates, leading to the selective transfer of phosphorus to the liquid phase, and that the addition of 1–5% hydrochloric acid corresponds to a phosphorus extraction rate in the range of 0.3–98%. When hydrochloric acid is added, a change in temperature and reaction time has a negligible effect on phosphorus. Phosphorus can be recovered using the liquid product obtained under the optimal hydrothermal reaction conditions (adding 5% HCl at 205 °C for 30 min). After adjusting the pH value and adding the magnesium source, struvite (MgNH4PO4·6H2O) can be precipitated quickly and with high purity. At a cost of USD 27.8/ton of sludge, this method can recover 94% of the phosphorus in the sludge, and the bioavailable phosphorus ratio of the product is 93%, therefore, providing an important alternative to existing phosphorus recovery technologies.

Low-temperature enhancement in the extraction of phosphorus from metallurgical-grade silicon by simultaneously re-constructing phosphorus-rich phases of Ca3P2 and CaAl2Si2-P

A novel method of combined Si-Al solvent refining with CaCl2-CaF2-CaO molten salt treatment for phosphorus removal from metallurgical-grade silicon was investigated. With the mass ratio of salt (45 wt.%CaCl2–45 wt.%CaF2–10 wt.%CaO) to the alloy (phosphorus-doped Al-Si) being 1:1, phosphorus-rich phases of Ca3P2 and CaAl2Si2-P were successfully reconstructed at 1250 °C for 1 h. After acid leaching, phosphorus content decreased from 3 wt.% to 0.24 wt.%, corresponding to a phosphorus removal rate of 91.95%.

Tarping and mulching effects on crop yields, profitability, and soil nutrients in a continuous no-till organic vegetable production system

Abstract Small-scale organic vegetable farms need strategies to overcome yield, labor, and economic challenges in transitioning to reduced and no-till practices. However, the production tradeoffs associated with different scale-appropriate management practices are not well documented for these operations. We evaluated crop yields, labor, profitability, and soil nutrients over four continuous years of management in Freeville, NY. Cabbage (Y1 and Y3) and winter squash (Y2 and Y4) were managed in permanent beds under four contrasting tillage systems: conventional rototilling to 20 cm depth (CT), shallow rototilling to 10 cm (ST), no-till (NT), and no-till with tarping (NTT), in which an impermeable, black polyethylene tarp was applied to the soil surface between crops. Within each tillage treatment, we compared three mulching systems: rye mulch (RM), compost mulch (CM), and no mulch (NM), where mulches were applied annually to each crop. Crop yields did not vary by tillage, except in RM, where yields were highest in CT and reduced in ST and NT over four years. Mulch treatments were a significant driver of crop yields. When compared to NM, RM reduced crop yields in the first two years and CM increased yields after the first year. Overall, RM systems had the lowest net returns and CM returns were equivalent to NM despite greater yields. No-till consistently required the greatest pre-harvest labor investment, up to two times greater than tilled systems with NM, and the lowest net returns. Labor requirements for NTT were greater than CT but up to 41% lower than NT, and profitability was equivalent to CT. Shallow tillage performed similar to CT across yield, labor, and profitability measures, except when combined with the use of RM. Compost mulching led to dramatic changes in soil properties after four years, including a 49% increase in total soil carbon, a 31% increase in total soil nitrogen, and a 497% increase in extractable phosphorus. Small farms adopting NT practices should: 1) consider the potential tradeoffs associated with annually applied organic mulches, and 2) integrate tarping to increase the profitability of NT over consecutive production years.

Effect of Fertilizer, Furrow Length, and Irrigation Flow Rate on Soil Nutrient and Yield of Apple Orchard

The objective of this study was to evaluate the impact of furrow irrigation with a length of 96, 144, and 192 m and a flow rate of between 0.2 and 0.4 Ls−1 on the leaching of nitrogen, phosphorus, and humus from dry subtropical soils in Azerbaijan. Moreover, the impact of six fertilizer levels, namely, control (without fertilizer), 10 t ha−1 of cow manure, N90P90K90 + 10 t ha−1 of cow manure, N120P90K90 + 10 t ha−1 of cow manure, N120P120K90 + 10 t ha−1 of cow manure, and N120P90K120 + 10 t ha−1 of cow manure, on the performance of apple orchards, has been examined. The findings indicate that the brown soils of the irrigated grassland exhibit normal humus, total nitrogen, and weak phosphorus levels, with a gradual decline observed in the lower layers. Applicable to the agricultural and subsurface layers, the aggregates are 0.25–1.0 mm in diameter, with an agricultural value of 12.9% and 21.8%, respectively. This indicates a poor structural condition of the apple orchard soil. The elevation of the water flow rate from 0.2 to 0.4 Ls−1 resulted in a greater extraction of humus, nitrogen, and phosphorus from the soil. Both water flow rates increased the nutrients and humus leaching from the soil. By extending the furrow length to 192 m, the losses of humus (3.25%), nitrogen (0.36%), and phosphorus (0.30%) from the soil in both water flows significantly increased in comparison to the 96‐m length. By extending the length of furrows to 192 m, the yield (21.97 t ha−1) was significantly reduced in comparison to the 96‐m length (22.31 t ha−1). As a consequence of the application of N120P90K120 + 10 t ha−1 of cow manure, the yield of 27.3 t ha−1 was significantly elevated in comparison to other fertilizer treatments and the control treatment (17.9 t ha−1). Therefore, management of fertilizer systems, furrow length, and water flow can improve soil fertility and plant yield by reducing erosion in the meadow‐brown soil of Azerbaijan.

Glycine-assisted phosphorus release and recovery from waste-activated sludge

This study reports a sustainable and green method for phosphorus (P) extraction and recovery from waste-activated sludge using glycine as a recyclable P-extraction agent.

Cleaner extraction of white phosphorus from phosphate rock through molten salt electrolysis

White phosphorus (P4) is an essential raw material for the production of phosphorus chemicals. The conventional carbothermal reduction process used to extract P4 from phosphate rock is known as energy intensive and environmentally polluting, posing obstacles to meeting the urgent global demands for clean production and carbon neutrality. Moreover, the low product purity restricts its application in high-value industries. This paper presents an original approach that is both simple and coke-free for extracting high-purity P4. The method involves electrolyzing dissolved phosphate rock in molten CaCl2 at a mild temperature. We undertake an in-depth investigation into the dissolution behavior of phosphate rock in molten CaCl2 and the electrolysis behavior of the melt. The experiments demonstrate the rapid dissolution of phosphate in the rock when exposed to molten CaCl2, reaching saturation within a short time (e.g., within 10 min at 850 °C). The dissolution of phosphate shows a preference over silicates present in the phosphate rock. The electrochemical reduction of PO43− in molten CaCl2 is electrochemically reversible, as observed at potential scan rates not exceeding 0.20 V s−1. The obtained P4 product through electrolysis is of higher purity compared to the industrial-grade commercial product produced via carbothermal reduction. The implementation of pre-electrolysis can further improve the purity of the product and the current efficiency of the electrolysis process. The theoretical electricity and carbon consumption in the electrolysis method are estimated to be 9.12 kWh and 0.53 kg, respectively, for every 1 kg of P4 produced. These values are lower than the conventional carbothermal reduction process. This cutting-edge electrolysis method represents a paradigm shift towards a more sustainable development of the phosphorus chemical industry, thereby showcasing its potential for revolutionizing the field.

Evaluation of the quality of some watermelon varieties grown on sandy soils

The objective of this study is to present the biochemical composition of 3 watermelon varieties: Dulce de Dăbuleni, Oltenia, De Dăbuleni, in the pedo-climatic conditions of the Dăbuleni area. The observations were made during 2022-2023 at SCDCPN Dăbuleni. The climatic conditions at SCDCPN Dăbuleni were favorable for the development of the watermelon culture. The experiment was located on a sandy soil, according to the method of randomized blocks in 4 repetitions. The following observations and determinations were made: the soil content in total nitrogen, extractable phosphorus, exchangeable potassium, organic carbon, pH; the biochemical content of the fruits: total dry matter, water, dry soluble substance, simple soluble carbohydrates, titratable acidity and vitamin C. The soil content in total nitrogen and exchangeable potassium was reduced, and in extractable phosphorus it was normal. Organic carbon showed values between 0.37%-0.56%, the state of soil supply being reduced towards the middle. The pH of the soil on which the experiment was placed oscillated between 7.1 and 7.12, indicating a neutral soil reaction. Cultivation technology specific to sandy soils was applied. The varieties Dulce de Dăbuleni and Oltenia stood out for the amount of vitamin C contained, while the De Dăbuleni variety had the lowest content in vitamin C (8.8 mg/100 g fresh substance). The content in soluble carbohydrates varied between 7.74% in the Oltenia variety and 10.49% in the Dulce de Dăbuleni variety.

Sugarcane Trash Biochar Released Least Extractable Phosphorus in an Acidic Incubated Soil

ABSTRACT Recycling of phosphorus (P) from feedstocks to soils can provide sustainability in agriculture. In our incubation study, we investigated the effects of adding cow manure-derived vermicompost (CMV), cow manure (CM), sugarcane trash biochar (STB), and triple super phosphate (TSP) to extractable P in a sandy loam soil. P was added to the soil at rates of 0, 50, 100, 200, and 300 mg kg−1 based on their total P contents. The amended soils were incubated for 1, 4, 8, and 16 weeks (wk) at room temperature and extractable P samples were measured (by water, Olsen, Mehlich-3 and Bray and Kurtz) and soil pH was monitored. After 1 wk of incubation, the extractable P values were 1.4 mg kg−1 with STB at the smallest while the highest was 79 mg kg−1 with TSP. The corresponding P values in the CMV and CM amended soils were 33 mg kg−1 and 31 mg kg−1. The reductions of extractable P from 1 to 16 wks of incubation were 40%, 35%, and 80% in the CMV, CM and TSP amended soils, respectively, while they increased from 1.43 mg kg−1 to 6.05 mg kg−1 ((320%) in the STB amended soil. Among the amendments, a significant positive relationship was observed between extractable P and the pH in soils amended with STB. The findings revealed that varying P extractability in soils depends on amendment types and duration of incubation. Sugarcane trash biochar did not exhibit an ability to substitute inorganic P fertilizer for assessing bioavailable P.

Selective recovery of phosphorus from the leachate of incinerated sewage sludge ash using the Zr-modified acid-leaching residue as adsorbent for two-fold resource utilization

Phosphorus, as an essential nutrient for plant growth, is crucial for the development of agriculture. In this study, a novel strategy using a zirconium-modified acid-leaching residue adsorbent (Zr-AR adsorbent) was proposed for the efficient and selective recovery of phosphorus from incinerated sewage sludge ash (ISSA). 0.2 mol/L HCl were optimized for the phosphorus extraction from ISSA. The acid-leaching residue with large pore structure and high specific surface area was first reused as a support to prepare Zr-AR adsorbent for a twofold resource utilization of ISSA. Without removing impurities from the leachate, the Zr-AR adsorbent could selectively adsorb phosphorus with a maximum phosphorus adsorption capacity of 53.1 ± 0.8 mg/g in the HCl system. During 5 phosphorus adsorption–desorption processes, the adsorption and desorption ratios of phosphorus remained stable at over 90 %, indicating the high stability of the Zr-AR adsorbent for selective phosphorus recovery. Without adjusting the pH, hydroxyapatite was produced from the phosphorus-rich solution with a phosphorus content of 33.4 ± 1.3 % P2O5, which could significantly promote the growth of ryegrass as a phosphorus fertilizer. The cost of the phosphorus recovery from ISSA was also preliminarily evaluated ($3.76 kg-P product), demonstrating the application potential of this strategy.

Utilization of bagasse as a soil amendment in sugarcane production on mineral soils in Florida

A 4-year study tested the feasibility of using bagasse as a soil amendment in sugarcane production on a commercial field with mineral soil in Florida. The experiment was established as a completely randomized design trial with three rates of fresh bagasse applications: approximately 5 cm of bagasse, 10 cm of bagasse, and 10 cm of bagasse + nitrogen (N), which are equivalent to 85 t ha–1, 170 t ha–1, and 170 t ha–1 + 336 kg ha–1 ammonium nitrate, respectively. A control (no bagasse and no N added) was also included. As each treatment and the control had three replicates, there were 12 plots (6.5 ha each in size) totaling over 77 ha. The high pH of the soils is a result of years of mixing underlying limestone (calcium carbonate) bedrock with the topsoil. Overall results indicate that bagasse application positively affected the accumulation of soil organic matter during a short-term period, resulting in higher water-holding capacity and lower bulk density. The high rate of bagasse application had a positive effect on N accumulation, extractable phosphorus (P) and potassium (K) contents during the short term. One single application of bagasse significantly increased the first-year sugarcane biomass and sugar yield by approximately 23%. An overall higher application rate of bagasse (10 cm) was recommended as it showed significantly positive effects on soil health indicators and had a longer effect on increasing sugarcane biomass and sugar yield. There is potential to incorporate bagasse into commercial sugarcane production grown on mineral soils in Florida.

Processing of phosphorites with extraction of phosphorus, obtaining calcium carbide and ferroalloy

The article considers the results of studying the thermodynamic computer modeling of the interaction of phosphorite (Karatau basin, Kazakhstan) with carbon and coke performed using the HSC-10 software package and electric smelting of the phosphorite with coke and steel shavings in an arc furnace. The modeling allowed us to determine the equilibrium extraction degrees of phosphorus into gas (Р&lt;sub&gt;2&lt;/sub&gt;, Р&lt;sub&gt;4&lt;/sub&gt;), silicon into ferroalloy in the form of iron silicides (FeSi&lt;sub&gt;2&lt;/sub&gt;, FeSi, Fe&lt;sub&gt;3&lt;/sub&gt;Si, Fe&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;3&lt;/sub&gt;, Si) and calcium into CaС&lt;sub&gt;2&lt;/sub&gt;. At temperatures above 1500 °C, regardless of the amount of iron, the extraction degree of phosphorus into gas is more 99%. The resulting ferroalloy contains 21.2-23.8% of Si, 1.6-2.8% of Al; the calcium carbide has a capacity of 288-325 dm&lt;sup&gt;3&lt;/sup&gt;/kg. The extraction degree of silicon into the alloy was 89.8%, calcium in CaC&lt;sub&gt;2&lt;/sub&gt; – 72.5%, phosphorus into gas – 99.4%. The ferroalloy, formed at the electric smelting of the Chulaktau phosphorite together with coke and steel shavings and containing 24.9-29.8% of Si, is FS25 grade ferrosilicon, and the formed calcium carbide has a capacity of 278-290 dm&lt;sup&gt;3&lt;/sup&gt;/kg and belongs to the third and second grades. The developed technology makes it possible to increase the degree of phosphorites’ comprehensive use two times (up to 87.5%).

Novel Extraction of Phosphorus using Interaction of Tricaprylylmethylammonium Chloride (TOMAC) with Biodegradable Mixture of Vegetable Oils

This work addresses the development of green formulation for phosphorus compound removal from aqueous solution via solvent extraction process. Several types of extractants, diluents and stripping agents were experimentally investigated and the best formulation was determined. Additionally, other parameters investigated were extractant and stripping agent concentrations. Results showed that TOMAC, a mixture of palm oil (PO) and sunflower oil (SO) as well as sodium chloride (NaCl) turned out to be the best extractant, diluent and stripping agent, respectively. Almost 100 % of 50 ppm of phosphorus were successfully extracted under optimum conditions of 0.3M TOMAC in a mixture of 50% PO + 50% SO. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the intermolecular bonding formation between phosphorus, vegetable oils and TOMAC molecules. Meanwhile, almost 96.5% of phosphorus can be recovered using 1.0M NaCl in two stages of stripping process. Stoichiometric studies showed that about one mole of TOMAC and NaCl were involved during the extraction and stripping reaction of phosphorus, respectively. It can be concluded that the solvent extraction with new green formulation containing TOMAC in interaction with vegetable oils seems to be one of the novel sustainable approaches in removing phosphorus from agricultural wastewater.

Soil quality Change Following Compost and Farmyard Manure Application in Maize and Cassava based Agro-ecosystems of Mvomero and Masasi -Tanzania

Soil quality is a major driver for improved crop production and sustainable food security. While crop response to soil applied organic amendments is widely studied, little has been done to establish the effect of such amendments on soil quality. Field experiments were conducted for two seasons (2019/20 and 2020/21) in Mvomero and Masasi districts to study the effects of compost (CP) and Farmyard manure (FYM) application on selected soil quality attributes. Both CP and FYM were applied on maize, and cassava plots at 0.0 t ha-1 (Control), 2.5 t ha-1, 5 t ha-1 and 7.5 t ha-1. Maize variety TMV-1 and Kiroba cassava variety were used as test crops in a Randomized Complete Block Design (RCBD) with three replications. Representative soil samples were collected before applying soil amendments and at the end of each season and analyzed for soil pH, Organic carbon (OC) and Extractable phosphorus (P). Assays of activities of ß-glucosidase and Phosphatase were performed on the samples as indicators of soil quality change. Results indicated that soil OC and soil extractable P increased with CP and FYM application rates at both sites. Activities of ß-glucosidase and Phosphatase increased in line with OC and extractable P, respectively. Application of CP or FYM at 5 t ha-1 and 7.5 t ha-1 resulted into statistically similar effects on soil OC, extractable P and activities of ß-glucosidase and Phosphatase. It was concluded that application of either CP or FYM at 5 t ha-1 can improve soil OC and P availability in degraded soils of Masasi and Mvomero, while activities of ß-glucosidase and phosphatase can serve to indicate such changes in soil quality.

Adsorption and immobilization of phosphorus from water and sediments using a lanthanum-modified natural zeolite: Performance, mechanism and effect

The challenge of effectively controlling endogenous pollution and achieving phosphate recovery remains a hotspot worldwide. The development of a passivator with high adsorption capacity and superior passivating effect is crucial for effective implementation in controlling endogenous pollution. In this study, a lanthanum-modified natural zeolite (LZ) and a lanthanum-modified magnetic zeolite (LMZ) were synthesized using precipitation and hydrothermal methods. Additionally, characterization and incubation experiments were conducted to assess the adsorption and passivation effects of the material. The results showed that the LZ and LMZ had excellent phosphorus (P) adsorption and passivation capabilities. LZ and LMZ exhibited remarkable adsorption capacities of 122.7 and 109.17 mg/g, respectively, surpassing those of most lanthanum-modified materials. The characterization showed that inner sphere complexation and electrostatic attraction served as the primary mechanisms facilitating phosphate adsorption. Moreover, LZ and LMZ were also used as sediment passivators to immobilize P within sediments. The addition of LZ and LMZ could not only control the release of P in overlying water but also transform unstable iron-bound phosphorus (BD-P) and organoclastic phosphorus (Org-P) into stable aluminum-bound phosphorus (OH-P) and calcium-bound phosphorus (H-P). The application of both LZ and LMZ could effectively reduce various forms of Bio-P in the sediment, including algal-available phosphorus (Al-P), sodium bicarbonate extractable phosphorus (Olsen-P), water-soluble phosphorus (WA-P), and iron oxide extractable phosphorus (Fe-P). The amount of LZ and LMZ needed for fixed Fe-P in sediments could be quantitatively calculated within a certain range. Since LMZ could be recovered from water under the action of an applied magnetic field and had better effects on the potential active phosphorus (Mob-P) and Bio-P in the sediments, LMZ could have high potential for use as a passivator for internal pollution control.

Extraction of Phosphorus from Sewage Sludge Ash—Influence of Process Variables on the Electrodialytic Process

Phosphorus is a critical, irreplaceable raw material, and developing methods to recover P from secondary sources such as sewage sludge ash (SSA) is crucial. Two-compartment electrodialytic extraction (2C-ED) is one method where an electric DC field is applied to extract P and separate heavy metals simultaneously. Several process parameters influence 2C-ED, and they influence each other mutually. This paper explores chemometrics modeling to give insight into the 2C-ED process and, specifically, optimization of the experimental parameters towards 80% P extraction. A projections-to-latent-structures model was constructed based on new 2C-ED experiments conducted with one SSA type. The model was stable (high correlation factor and predictive power). Variable importance in the projection (VIP) plots showed that the influence of the variables was in the order: current &gt; duration &gt; L:S ratio &gt; stirring velocity &gt; dispersion solution (weak acid or distilled water). Contour plots were used for exploring different P extraction strategies. For example, more P mass per unit current was extracted at an L:S ratio of 7 compared to L:S 14. This shows that treating a thicker SSA suspension is preferable to optimize the current efficiency. The chemometric model proved valuable for optimizing the 2C-ED process and future scale-up.