High Phosphate Concentrations Research Articles

Monitoring localized changes of Cr(VI) bioavailability related to root-induced changes around rice roots

Transformation between Cr(III) and Cr(VI) occurs in Cr-contaminated soils. Although redox conditions and biotic/microbial activity are known to be important factors in determining Cr transformation and accumulation in soil-rice systems, how spatial trends and specific soil processes regulate Cr behaviour around lowland/flooded rice roots are poorly understood. In this study, the Cr(VI) bioavailability was evaluated using the diffusive gradients in thin film (DGT) technology. Root activity reduced Cr(VI) bioavailability. The Cr(VI) flux near rice roots was 1.27–3.92 times lower than that in bulk soil (0.94 ng cm−2 h−1). The radial extension of the strong influence zone (R1) in the rhizosphere of C-LYZ was smaller than that in Hui-LY985. Although Fe(II) and S2− were involved in Cr(VI) reduction, they were not the primary influence, especially for the rhizosphere region. The high phosphate concentration in the C-LYZ rhizosphere hindered Cr(VI) uptake. The DGT technique overcomes the limitations of traditional research methods, revealing the spatial variability in Cr(VI) and its interactions with other elements in the rhizosphere, thereby providing theoretical basis for bioavailability evaluation and remediation of Cr-contaminated soils.

Strategies for optimizing biovivianite production using dissimilatory Fe(III)-reducing bacteria.

Vivianite (Fe3(PO4)2·8H2O), a sink for phosphorus, is a key mineralization product formed during the microbial reduction of phosphate-containing Fe(III) minerals in natural systems, and also in wastewater treatment where Fe(III)-minerals are used to remove phosphate. As biovivianite is a potentially useful Fe and P fertiliser, there is much interest in harnessing microbial biovivianite synthesis for circular economy applications. In this study, we investigated the factors that influence the formation of microbially-synthesized vivianite (biovivianite) under laboratory batch systems including the presence and absence of phosphate and electron shuttle, the buffer system, pH, and the type of Fe(III)-reducing bacteria (comparing Geobacter sulfurreducens and Shewanella putrefaciens). The rate of Fe(II) production, and its interactions with the residual Fe(III) and other oxyanions (e.g., phosphate and carbonate) were the main factors that controlled the rate and extent of biovivianite formation. Higher concentrations of phosphate (e.g., P/Fe = 1) in the presence of an electron shuttle, at an initial pH between 6 and 7, were needed for optimal biovivianite formation. Green rust, a key intermediate in biovivianite production, could be detected as an endpoint alongside vivianite and metavivianite (Fe2+Fe3+2(PO4)2.(OH)2.6H2O), in treatments with G. sulfurreducens and S. putrefaciens. However, XRD indicated that vivianite abundance was higher in experiments containing G. sulfurreducens, where it dominated. This study, therefore, shows that vivianite formation can be controlled to optimize yield during microbial processing of phosphate-loaded Fe(III) materials generated from water treatment processes.

Assessing the Impacts of Lead Corrosion Control on the Microbial Ecology and Abundance of Drinking-Water-Associated Pathogens in a Full-Scale Drinking Water Distribution System.

Increases in phosphate availability in drinking water distribution systems (DWDSs) from the use of phosphate-based corrosion control strategies may result in nutrient and microbial community composition shifts in the DWDS. This study assessed the year-long impacts of full-scale DWDS orthophosphate addition on both the microbial ecology and density of drinking-water-associated pathogens that infect the immunocompromised (DWPIs). Using 16S rRNA gene amplicon sequencing and droplet digital PCR, drinking water microbial community composition and DWPI density were examined. Microbial community composition analysis suggested significant compositional changes after the orthophosphate addition. Significant increases in total bacterial density were observed after orthophosphate addition, likely driven by a 2 log 10 increase in nontuberculous mycobacteria (NTM). Linear effect models confirmed the importance of phosphate addition with phosphorus concentration explaining 17% and 12% of the variance in NTM and L. pneumophila density, respectively. To elucidate the impact of phosphate on NTM aggregation, a comparison of planktonic and aggregate fractions of NTM cultures grown at varying phosphate concentrations was conducted. Aggregation assay results suggested that higher phosphate concentrations cause more disaggregation, and the interaction between phosphate and NTM is species specific. This work reveals new insight into the consequences of orthophosphate application on the DWDS microbiome and highlights the importance of proactively monitoring the DWDS for DWPIs.

New model of long-term changes in spatiotemporal patterns of water quality across Shatt-Al-Arab River by applying GIS technique, from 1976 to 2020

PurposeUsing a combination of the geographical information system (GIS) and the Canadian water quality index (WQI), the current study sought to provide a long-term general assessment of the water quality of the Shatt Al-Arab River (SAAR), focusing on its suitability for living organisms. Likewise, SPSS statistics was used to develop a nonlinear WQI regression model for the study area.Design/methodology/approachThe study required four decades of data collection on some environmental characteristics of river water. After that, calculate the WQI and conduct the spatial analysis. Eight variables in total, including water temperature, dissolved oxygen, potential hydrogen ions, electrical conductivity (EC), biological oxygen demand, turbidity, nitrate and phosphate, were chosen to calculate the WQI.FindingsThroughout the study periods, the WQI values varied from 55.2 to 79.83, falling into the categories of four (marginal) and three (fair), with the sixth period (2007–2008) showing the most decline. The present research demonstrated that the high concentration of phosphates, the high EC values, and minor changes in the other environmental factors are the major causes of the decline in water quality. The variations in ecological variables' overlap are a senior contributor to changes in water quality in general. Notably, using GIS in conjunction with the WQI has shown to be very effective in reducing the time and effort spent on investigating water quality while obtaining precise findings and information at the lowest possible expense. Calibration and validation of the developed model showed that this model had a perfect estimate of the WQI value. Due to its flexibility and impartiality, this study recommends using the proposed model to estimate and predict the WQI in the study area.Originality/valueEven though the water quality of the SAAR has been the subject of numerous studies, this is the only long-term investigation that has been done to evaluate and predict its water quality.

Impact of Biochar Applications on Tropical Soils under Different Land-use Regimes

The application of biochar to agricultural soils can either be beneficial or detrimental, as well as no clear effect to soils and crops. Therefore, the aim of our study was to investigate the effects of biochar addition on soil chemical and biological properties and nutrient leaching in three tropical soils with different types of land-use (forest, non-intensive and intensive farming). The soils were amended with and without 2% coconut shell (CS) and rice husk (RH) biochars by weight and incubated for up to 360 days. To assess the impact of biochar on soil leaching, 27 unplanted soil columns from the same types of land-use were also amended with and without 2% CS and RH biochars by weight. Five leaching experiments were conducted by passing through 100 ml of deionised water via each of the glass columns containing soil. The biochar addition significantly increased (P<0.05) the soil pH and total carbon, but had a marginal effect on CEC and had a limited effect on microbial activity. Biochar treatments reduced ammonium leaching in the forest soil, but had no clear effect on the other two soils. Our data showed that biochar application at a lower rate can ameliorate soil acidic conditions, enhance carbon sequestration and adsorb ammonium ion. However, the success depends on soil and biochar properties and land-use. The biochar samples studied have a limited capacity to reduce nitrate and phosphate leaching due to high biochar phosphate content.

Integrated Phytobial Remediation of Dissolved Pollutants from Domestic Wastewater through Constructed Wetlands: An Interactive Macrophyte-Microbe-Based Green and Low-Cost Decontamination Technology with Prospective Resource Recovery

Macrophytes have the potential to withstand pollutant-induced stress and can be used to clean contaminated water using phyto-extraction, phyto-degradation, phyto-filtration, phyto-stimulation, and phyto-volatilization technique(s). Phytoremediation through constructed wetlands (CWs) for eliminating inorganic and organic pollutants from household sewage and wastewater has attracted scientific attention. CWs are artificially engineered treatment systems that utilize natural cycles or processes involving soils, wetland vegetation, and plant and soil-associated microbial assemblages to remediate contaminated water and improve its quality. Herein, we present a detailed assessment of contaminant removal effectiveness in different CW systems, i.e., free-water surface or surface-flow constructed wetlands (FWSCWs/SFCWs), subsurface-flow constructed wetlands (SSFCWs), and hybrid constructed wetlands (HCWs). Several wetland floral species have been reported as potential phytoremediators, effectively reducing aquatic contamination through biodegrading, biotransforming, and bioaccumulating contaminants. Water hyacinth (Pontederia crassipes) is one of the most resistant macrophytes, capable of tolerating high nitrate (NO3−) and phosphate (PO42−) concentrations. Other aquatic weeds also effectively alleviate biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), and pathogen levels and ameliorate the impact of different ionic forms of nitrogen (N), phosphorus (P), and trace elements (TEs). The review primarily focuses on using hydrophyte(s)-microbe(s) associations in different CWs as an essential phytoremediation tool for sustainable management of freshwater ecosystems, ecorestoration, and prospective resource recovery, favoring a circular bioeconomy (CBE).

Genomic and Proteomic Analysis of Pseudomonas aeruginosa Isolated from Industrial Wastewater to Assess Its Resistance to Antibiotics

Industrial wastewater usually contains a large amount of organic and inorganic pollutants, and many microorganisms. However, the types of microorganism present in industrial wastewater are still unclear. The aim of this study was to analyze the physicochemical properties and drug resistance of Pseudomonas aeruginosa isolated from industrial wastewater containing high concentrations of sulfate compounds. Pseudomonas aeruginosa was isolated from industrial wastewater from industrial produce with high concentrations of sulfate and phosphate, and mass spectrometry identification, gene identification, biochemical analysis and genomic and proteomic property identification were carried out. According to the results of matrix-assisted flight mass spectrometry and 16S rDNA sequencing, the isolated bacterium was identified as Pseudomonas aeruginosa, and was positive for reactions of ONPG, ACE, GLU, MNE, etc. Through growth experiments, it can be seen that Pseudomonas aeruginosa had a significant growth rate in the LB medium. Antibiotic sensitivity tests showed that Pseudomonas aeruginosa was susceptible to most antibiotics and moderately resistant to Polymyxin B and Polymyxin E. The drug resistance gene experiment showed that Pseudomonas aeruginosa had the gyrB gene related to antibiotic resistance. Proteomic analysis revealed that six proteins were involved in antibiotic resistance. This experiment isolated Pseudomonas aeruginosa from industrial produce wastewater containing high concentrations of sulfate and phosphate ions, providing a new perspective for further research on the characteristics and drug resistance of microorganisms in industrial wastewater and their potential functions when using them to deal with environmental pollution.

Phosphate burden induces vascular calcification through a NLRP3-caspase-1-mediated pyroptotic pathway

AimsThe aim of this study is to clarify the role of NLRP3 inflammasome in phosphate burden-induced vascular smooth muscle cell (VSMC) calcification. Main methodsVSMC calcification was induced using a high concentration of inorganic phosphate. After pharmacological inhibition or genetic silencing of the NLRP3 inflammasome, pyroptosis, or potassium efflux, the cells were examined by RT-qPCR, immunofluorescence, and western blotting to identify the NLRP3-mediated pathway for VSMC calcification. Key findingsCalcified VSMCs with α-smooth muscle actin (α-SMA) disarray presented features of pyroptosis, including caspase-1 maturation, cleaved gasdermin D (GSDMD), and a high supernatant level of lactate dehydrogenase A. Pharmacological inhibitions of caspase-1 and pyroptosis attenuated VSMC calcification, whereas interleukin-1β receptor antagonism did not. Unlike canonical NLRP3 activation, osteogenic VSMCs did not upregulate NLRP3 expression. However, NLRP3 genetic silencing or inhibitions, which targets different domains of the NLRP3 protein, could ameliorate VSMC calcification by aborting caspase-1 and GSDMD activation. Furthermore, potassium efflux through the inward-rectifier potassium channel, and not through the P2X7 receptor, triggered NLRP3 inflammasome activation and VSMC calcification. SignificanceIn the present study, we identified a potassium efflux-triggered NLRP3-caspase-1-mediated pyroptotic pathway for VSMC calcification that is unique and different from the canonical NLRP3 inflammasome activation. Therefore, targeting this pathway may serve as a novel therapeutic strategy for vascular calcification.

Comparison of DNA preservation and ATR-FTIR spectroscopy indices of cortical and trabecular bone of metacarpals and metatarsals

Shape, size, composition, and function of the bones in the human body vary on the macro, micro and nanoscale. This can influence changes caused by taphonomy and post-mortem preservation, including DNA. Highly mineralised compact bone is less susceptible to taphonomic factors than porous trabecular bone. Some studies imply that DNA can be better preserved in trabecular bone, due to remnants of the soft tissue or bacteria better digesting organic matter while not digesting DNA. The aim of this study was to understand the differences between compact (diaphyses) and trabecular (epiphyses) bone on a molecular level and thus the reasons for the better preservation of the DNA in the trabecular bone. The powder obtained from epiphyses and diaphyses of metacarpals and metatarsals was analysed using ATR-FTIR spectroscopy and compared. Samples with poorest DNA preservation originated from diaphyses, predominantly of metatarsals. They were characterised by higher concentrations of phosphates and crystallinity, while lower collagen quality in comparison to samples with the best DNA preservation. Epiphyses presented higher concentrations of better-preserved collagen while diaphyses had higher concentrations of carbonates and phosphates and higher crystallinity. Due to better-preserved collagen in the epiphyses, the soft tissue remnants hypothesis seems more likely than the bacteria hypothesis.

Insight into Impact of Phosphate on the Cotransport and Corelease of Eu(III) with Bentonite Colloids in Saturated Quartz Columns

Understanding the fate and transport of radionuclides in porous media reduces the risk of contaminating soils and groundwater systems. While the cotransport of bentonite colloids (BC) with radionuclides in saturated media is well documented, the role of phosphate (P) in the colloid-driven transport of radionuclides in saturated porous media is still unaddressed; in particular, phosphate increases the mobilities of radionuclides in porous media, which should be subjected to an environmental risk assessment and model construction. In this work, the effects of phosphate on the transport and release of Eu(III) in different colloid systems (P-Eu(III), P-BC, P-BC-Eu(III)) was investigated with a fundamental colloid chemistry approach and a range of characterization techniques. The results showed that intrinsic europium colloids with size of 685 nm were formed by precipitation with phosphate, which affected the mobility of Eu(III) due to colloid stability and physical straining. Phosphate enhanced BC and BC-Eu(III) transport, and a high phosphate concentration promoted BC transport by eliminating physical straining and enhancing the electrostatic repulsions. The crystal structure of EuPO4 was not destroyed by the subsequent introduction of BC, which carried EuPO4 for further migration. However, when phosphate, bentonite and Eu(III) coexisted in a colloid suspension, the phosphate promoted Eu(III) transport by preferentially interacting with the BC to form ternary BC-P-Eu(III) pseudo-colloids rather than forming the intrinsic EuPO4 colloids. The synergetic role of P and BC on Eu(III) transport involved a relatively complex process and was not a simply additive effect. The findings in this work highlight the significance of phosphate in controlling the fate and transport of Ln(III)/Am(III) radionuclides in the presence of intrinsic colloids and pseudo-colloids in P-rich colloid-bearing environments.

Phosphate in Aqueous Solution Adsorbs on Limestone Surfaces and Promotes Dissolution

The use of large quantities of phosphorus-containing fertilizers has resulted in an increase in phosphorus content in the groundwater system, and phosphorus can be adsorbed on the surface of carbonate rocks, affecting their dissolution process and thus carbon sequestration and sink enhancement in carbonate rocks. Therefore, in this study, limestone was exposed to 2 mg/L and 100 mg/L phosphate solutions for 12 d through static batch adsorption experiments. The hydrochemical results showed that in 100 mg/L phosphate solution, a substitution reaction occurred to produce CaHPO4 precipitate, while the concentration of each ion in 2 mg/L phosphate solution was relatively stable and in dynamic equilibrium; combined with XRD and XPS analyses, the main mechanism of phosphate adsorption may be chemical precipitation, which is preferentially adsorbed to Ca sites on carbonate rocks, and the surface deposits are mainly CaHPO4 and a small amount of Mg2PO4(OH). The FTIR spectra were obtained in the range of 1040 cm−1–1103 cm−1 for observed phosphate vibrations, and the υ3 (asymmetric stretching) mode was more significant in the experimental group with a higher phosphate concentration. Raman spectra located near 149 cm−1 and 275 cm−1 involved Ca2+ or Mg2+ relative translations and vibrations, corroborating the FTIR spectroscopic results; a combination of XRD, XPS, FTIR, and Raman spectra confirmed that phosphate adsorption on limestone may be due to the interaction of electrostatic, chemical precipitation, and ligand exchange mechanisms. In addition, the SEM-EDS results showed that, with the combined effect of the water–rock chemical reaction and physical adsorption, metal–phosphorus phase precipitation was formed on the limestone surface, which promoted the dissolution of limestone and may have an unfavorable effect on the carbon sequestration and sinking of carbonate rocks.

One Advantage of Being Polyploid: Prokaryotes of Various Phylogenetic Groups Can Grow in the Absence of an Environmental Phosphate Source at the Expense of Their High Genome Copy Numbers.

Genomic DNA has high phosphate content; therefore, monoploid prokaryotes need an external phosphate source or an internal phosphate storage polymer for replication and cell division. For two polyploid prokaryotic species, the halophilic archaeon Haloferax volcanii and the cyanobacterium Synechocystis PCC 6803, it has been reported that they can grow in the absence of an external phosphate source by reducing the genome copy number per cell. To unravel whether this feature might be widespread in and typical for polyploid prokaryotes, three additional polyploid prokaryotic species were analyzed in the present study, i.e., the alphaproteobacterium Zymomonas mobilis, the gammaproteobacterium Azotobacter vinelandii, and the haloarchaeon Halobacterium salinarum. Polyploid cultures were incubated in the presence and in the absence of external phosphate, growth was recorded, and genome copy numbers per cell were quantified. Limited growth in the absence of phosphate was observed for all three species. Phosphate was added to phosphate-starved cultures to verify that the cells were still viable and growth-competent. Remarkably, stationary-phase cells grown in the absence or presence of phosphate did not become monoploid but stayed oligoploid with about five genome copies per cell. As a negative control, it was shown that monoploid Escherichia coli cultures did not exhibit any growth in the absence of phosphate. Taken together, all five polyploid prokaryotic species that have been characterized until now can grow in the absence of environmental phosphate by reducing their genome copy numbers, indicating that cell proliferation outperforms other evolutionary advantages of polyploidy.

Saturating growth rate against phosphorus concentration explained by macromolecular allocation.

The saturating relationship between phytoplankton growth rate and environmental nutrient concentration has been widely observed, yet the mechanisms behind the relationship remain elusive. Here, we use a mechanistic model of phytoplankton and show that the saturating relationship between growth rate and phosphorous concentration can be interpreted by intracellular macromolecular allocation. At low nutrient levels, the diffusive nutrient transport linearly increases with the phosphorous concentration, while the internal phosphorous requirement increases with the growth rate, leading to a non-linear increase in the growth rate with phosphorous. This increased phosphorous requirement is due to the increased allocation to biosynthetic and photosynthetic molecules. The allocation to these molecules reaches a maximum at high-phosphorous concentration, and the growth rate no longer increases despite the rise in phosphorous concentration. The produced growth rate and phosphorous relationships are consistent with the data of phytoplankton across taxa. Our study suggests that the key control of phytoplankton growth is internal, and nutrient uptake is only a single step in the overall process. IMPORTANCE The Monod equation has been used to represent the relationship between growth rate and the environmental nutrient concentration under the limitation of this respective nutrient. This model often serves as a means to connect microorganisms to their environment, specifically in ecosystem and global models. Here, we use a simple model of a marine microorganism cell to illustrate the model's ability to capture the same relationship as Monod, while highlighting the additional physiological details our model provides. In this study, we focus on the relationship between growth rate and phosphorus concentration and find that RNA allocation largely contributes to the commonly observed trend. This work emphasizes the potential role our model could play in connecting microorganisms to the surrounding environment while using realistic physiological representations.

Simultaneous removal of fluoride and phosphate from semiconductor wastewater via chemical precipitation of calcium fluoride and hydroxyapatite using byproduct of recycled aggregate

Semiconductor wastewater with high concentrations of fluoride and phosphate is an environmental issue that cannot be ignored. Moreover, the byproduct of recycled aggregates, concrete fines, cannot be reused in concrete manufacturing, which is a key issue to address for the sustainable development of the concrete industry. The objective of this study was to tackle the crucial environmental issues of these two industries by developing concrete fines as an alternative material to treat semiconductor wastewater. The chemical precipitation of calcium fluoride and hydroxyapatite in the presence of concrete fines was determined as the mechanism underpinning the removal of fluoride and phosphate in wastewater. Owing to the wide range of contaminant concentration and solution pH and the possibility of multi-stage treatment, the effects of the initial contaminant concentration (F: 100–1000 mg/L; P: 20–200 mg/L) and solution pH (pH: 2–7) on the removal reactions were determined. The highest F and P removal percentages were more than 99%, and the final F and P concentrations met the effluent standard (F: 15 mg/L, P: 1.3 mg/L). The removal reactions of F and P are generally in competition, and the removal of F has priority over the removal of P. The pseudo-second-order model can describe the kinetics of the removal reactions well. The formation of fluorapatite can reduce the F concentration below the concentration achievable by CaF2 precipitation alone. Furthermore, using the byproduct of recycled aggregates instead of conventional chemicals to treat semiconductor wastewater is promising in terms of reducing CO2 emissions, and prospective applications are discussed. This study can lead to the development of a sustainable and clean process for semiconductor wastewater treatment using byproducts from the concrete industry.

Research on square wave pulsed electrochemical phosphate recovery technology by Pt graphene foam metal electrode

Currently, using electrochemical precipitation techniques for phosphate removal and recovery in hydroxyapatite (HAP) or calcium phosphate (CaP) form is widely used, while the high energy consumption of electrochemical precipitation is a major obstacle to its application. In this study, a square wave pulsed electrochemical phosphate precipitation method was developed, which achieved phosphate pollution control and phosphate resource recovery and reuse at the same time. The square wave pulsed electrochemical phosphate recovery system was constructed and a Pt-rGO/CuF electrode was synthesized and evaluated. This result indicated that the Pt-rGO/CuF electrode had the highest electrocatalytic activity, the better electrical conductivity, and the smallest electron transport barrier. Under optimal operation conditions, the phosphate removal efficiency and specific energy consumption of Pt-rGO/CuF were 64.2% and 21.49 kWh kg−1, respectively. The Pt-rGO/CuF electrode demonstrated the best electrochemical precipitation reaction performance. The Pt-rGO/CuF electrode was applied to multiple types of actual wastewater, and the results showed that it has better application prospects in both low (7.75 mg L−1) and high (66 mg L−1) phosphate concentration wastewater, the phosphate removal efficiency was 75.5% and 59.1%, respectively. Compared with traditional chemical precipitation, the electrochemical precipitation method saved $2.88 per kg P and $57.57 per kg P, respectively.

Development of Nonwoven Fibrous Materials Based on Poly-3-Hydroxybutyrate with a High Content of α-Tricalcium Phosphate.

α-tricalcium (α-TCP) phosphate is widely used as an osteoinductive biocompatible material, serving as an alternative to synthetic porous bone materials. The objective of this study is to obtain a highly filled fibrous nonwoven material composed of poly-3-hydroxybutyrate (PHB) and α-TCP and to investigate the morphology, structure, and properties of the composite obtained by the electrospinning method (ES). The addition of α-TCP had a significant effect on the supramolecular structure of the material, allowing it to control the crystallinity of the material, which was accompanied by changes in mechanical properties, FTIR spectra, and XRD curves. The obtained results open the way to the creation of new osteoconductive materials with a controlled release of the source of calcium into the living organism.

A comparative study of several types of indices for river quality assessment

Abstract Water is vital for humans, plants, and animals; unfortunately, some anthropogenic activities adversely alter water quality (WQ). Many indicators can be used for WQ assessment; fortunately, extensive data can be simplified by using WQ indices (WQIs). The main difference among WQIs lies in the way of assessing pollution and the number and types of WQ indicators used; therefore, the selection of a reliable WQI should be the first step. This research aimed to compare several types of indices and evaluate their effectiveness. Eighteen sampling sites were monitored, and the selected indices showed different results. Biological indices exhibited a significant statistical correlation and yet different quality results. In addition, biological WQIs showed different outcomes from the physicochemical index. The high concentrations of phosphates, fecal coliforms, and biological oxygen demand, found in most rivers, were responsible for adversely influencing the quality results of the physicochemical index; however, their high concentrations found in some sampling sites had no adverse effect on the macroinvertebrate's existence; therefore, biological WQ assessment showed better quality results than the physicochemical index. The Rapid Bioassessment Protocol index, based on visual habitat observations, proved to be an easy way to classify WQ and an adequate replacement for biological indices.

Adsorption of phosphate in aqueous solution by ash from the fruit peel of Caryocar coriaceum Wittm: adsorption characteristics and behavior.

High phosphate concentrations in natural waters are associated with eutrophication problems that negatively affect the fauna and flora of ecosystems. As an alternative solution to this problem, we evaluated the adsorptive capacity of the fruit peel ash (PPA) of Caryocar coriaceum Wittm and its efficiency in removing phosphate (PO43-) from aqueous solutions. PPA was produced under an oxidative atmosphere and calcinated at 500°C. The XRF and EDS analyses of PPA after contact with an aqueous PO43- solution showed an increase in its PO43- content, thus confirming the adsorption of PO43-. The Elovich and Langmuir models are the ones fitting the kinetics and the equilibrium state of the process, respectively. The highest PO43- adsorption capacity was approximately 79.50mgg-1 at 10°C. PO43- adsorption by PPA is a spontaneous, favorable, and endothermic process involving structural changes. The highest removal efficiency was 97.08% using a 100mg.L-1 PO43- solution. In sight of this, PPA has shown potential as an excellent natural bioadsorbent.

Effects of phosphorus availability on macroalgae: A review

Phosphorous is considered as an essential nutrient for life. Its availability in the water dictates the primary productivity, including macroalgae. In this paper, peer-reviewed articles reporting the effects of phosphorous on macroalgae for the past decades and up to the present were reviewed and recapitulated. The literature revealed that while phosphorous is one of the limiting nutrients in an open ocean, eutrophication in some coastal areas, which is fueled by anthropogenic activities, contributes to the excess phosphorous resulting in the occurrence of green tides. The general influences of phosphorous availability to many macroalgae were enhanced growth and biomass, especially with the interaction effect with nitrogen. However, some studies reported that the high concentration of phosphorous has deleterious effects on macroalgae. Hence, future studies are needed to fully understand the role of phosphorous availability in macroalgae.

Optimization of an electrochemical direct air capture process with decreased CO2 desorption pressure and addition of background electrolyte

An electrochemical process based on pH-swing has been proposed recently to regenerate spent alkaline absorbent from direct air capture (DAC). In this work, we experimentally investigated and theoretically simulated two optimization strategies to further reduce the energy consumption of such novel electrochemical process. First, partial vacuum was applied to the gas phase during CO2 desorption to increase the gas production rate. The energy consumption of the electrochemical cell decreased by 12 to 15% when the CO2 partial pressure in the gas phase was reduced from 0.9 to 0.3 atm. Second, phosphate and sulphate were tested as background electrolyte to the alkaline absorbent, reducing the energy consumption by minimizing the ohmic losses in the electrochemical cell. The optimal concentration for phosphate was 0.1 M, while the CO2 production rate was limited by either the total carbon feeding rate or the high acidifying solution pH at higher concentrations of phosphate. Moreover, due to the low pKa and high molar conductivity of sulphate compared to phosphate, sulphate addition showed an even lower energy consumption than phosphate addition. Finally, the lowest experimental energy consumption was 247 kJ mol−1 CO2 achieved with CO2 partial pressure of 0.3 atm and 0.1 M of sulphate addition at current density of 150 A m−2 while our mathematical model predicted a theoretical minimum energy consumption of 138 kJ mol−1 under the same condition. Overall, the investigated optimization strategies advanced the development of an energy-efficient electricity-driven process for direct air capture.