Phosphorus removal from eutrophic waters with an aluminium hybrid nanocomposite

An excess of phosphorus (P) is the most common cause of eutrophication of freshwater bodies. Thus, it is imperative to reduce the concentration of P to prevent harmful algal blooms. Moreover, recovery of P has been gaining importance because its natural source will be exhausted in the near future. Therefore, the present work investigated the removal and recovery of phosphate from water using a newly developed hybrid nanocomposite containing aluminium nanoparticles (HPN). The HPN-Pr removes 0.80 ± 0.01 mg P/g in a pH interval between 2.0 and 6.5. The adsorption mechanism was described by a Freundlich adsorption model. The material presented good selectivity for phosphate and can be regenerated using an HCl dilute solution. The factors that contribute most to the attractiveness of HPN-Pr as a phosphate sorbent are its moderate removal capacity, feasible production at industrial scale, reuse after regeneration and recovery of phosphate.The authors acknowledge the Foundation for Science and Technology (FCT) Project SFRH/BD/39085/2007 for the financial support

Phosphorus removal by a fixed-bed hybrid polymer nanocomposite biofilm reactor

Eutrophication is one of the main challenges regarding the ecological quality of surface waters, phosphorus bioavailability being its main driver. In this context, a novel hybrid polymer nanocomposite (HPN-Pr) biofilm reactor aimed at integrated chemical phosphorus adsorption and biological removal was conceived. The assays pointed to removal of 1.2 mg P/g of reactive phosphorus and 1.01 mg P/g of total phosphorus under steady-state conditions. A mathematical adsorption–biological model was applied to predict reactor performance, which indicated that biological activity has a positive effect on reactor performance, increasing the amount of reactive phosphorus removed.The authors acknowledge the Portuguese Foundation for Science and Technology for the financial support under Project SFRH/BD/39085/2007

New eco-efficient polymers for phosphorus recovery

Tese de doutoramento em Ciência e Engenharia de Polímeros e CompósitosIn the last 50 years a considerably decline on quality of superficial natural waters, in special for aquatic environments, where the water residence time is higher (more than one year), has been witnessed. Discharge of wastewaters without appropriate treatment, leaching of fertilisers and slurry from agricultural land resulted in a massive input of nutrients to superficial waters, especially phosphorus and nitrogen. As a consequence of this nutrient enrichment, aquatic plants start to overgrow impairing the waters, a process describe as eutrophication. The eutrophication prevents the use of water for recreational proposes, increases the cost of water purification for human and animal consumption and has severe consequences for biodiversity. Therefore, the main of this thesis was to develop a new polymeric material able to remove phosphorus from eutrophic waters without any environmental contamination. Hybrid nanocomposites containing aluminium nanoparticles were prepared by sol-gel reaction in the melt in an internal mixer. Polypropylene (PP), polypropylene grafted with maleic anhydride (PP-g- MA) and poly(ethylene vinyl acetate) (EVA) were used as organic components to prepared the nanocomposites. Two different aluminium precursors, aluminium isopropoxide (Al(Pr-i-O)3) and aluminium acetylacetonate (Al(acac)3) were used to produce the aluminium nanoparticles. Several analytical techniques were used to characterize the nanocomposites produced. The results shows that aluminium precursor with short organic chain (Al(Pr-i-O)3) allow faster and extensive reactions without a post step treatment. The nanoparticles are smaller and well dispersed. Regarding to phosphorus removal efficiency, the nanocomposite based of PP was the one that exhibited better performance. Therefore, this material was also produced in a twin-screw to evaluate the scale-up production. The results in a pilot scale, where real eutrophic water was treated using this material, confirm that it is able to remove phosphorus from natural waters. Moreover, it can be used several times and the phosphorus can be recovery.Nos últimos 50 anos tem-se assistido a uma diminuição considerável na qualidade das águas superficiais, especialmente em meios aquáticos onde o tempo de residência da água é elevado (superior a 1 ano). Descargas de águas residuais sem tratamento suficiente, lixiviação de fertilizantes e escorrências de terrenos agrícolas, têm contribuído para a introdução massiva de nutrientes, especialmente fósforo e azoto, nas águas superficiais. Como consequência deste enriquecimento, plantas aquáticas começaram a crescer descontroladamente comprometendo a qualidade das águas, um processo denominado por eutrofização. A eutrofização impede o uso dos meios aquáticos para fins lúdicos, aumenta os custos de purificação da água para consumo humano e animal e tem graves consequências para a biodiversidade. Posto isto, o objectivo da presente tese foi desenvolver um novo material polimérico capaz de captar o fósforo de águas eutrofizadas sem provocar contaminações. Para esse efeito, foram preparados por reação de sol-gel no fundido num misturador interno, vários nanocompositos contendo nanoparticulas de alumínio. Polipropileno (PP), polipropileno enxertado com anidrido maleico (PP-g-MA) e poli(etileno vinil acetato) (EVA), foram usados como componentes orgânicos na preparação dos nanocompositos. Dois precursores de alumínio, alumínio isopropoxido (Al(Pr-i- O)3) e alumínio acetilacetonato (Al(acac)3) foram usados para produzir as nanoparticulas de alumínio. Várias técnicas analíticas foram empregues para caracterizar os nanocompositos produzidos. Os resultados obtidos mostram que o precursor de alumínio com menor cadeia orgânica (Al(Pr-i- O)3) permitiu reações mais rápidas e extensas sem necessidade de tratamento posterior. As nanoparticulas geradas são pequenas e encontram-se dispersas homogeneamente. Relativamente à eficiência na remoção de fósforo, o nanocomposito baseado no PP foi o que exibiu a melhor performance. Posteriormente, este material foi produzido numa extrusora duplo fuso de modo a avaliar a sua produção a nível industrial. Resultados obtidos num estudo à escala piloto, onde água real foi tratada usando este material, confirmaram a sua eficiência na remoção de fósforo. Por ultimo, este pode ser usado consecutivamente e o fósforo recuperado

Phosphate reclamation from water using Douglas fir biochar Fe/Mg-LDH Composites

Eutrophication, caused by phosphate, can be detrimental both for the aquatic environment and human health. This research aims to provide deep knowledge about the adsorption properties of low-cost Fe/Mg layered double hydroxide modified biochar (LDHBC) for removal of phosphate from aqueous solution. Firstly, Fe/Mg layered double hydroxide (LDH) was synthesized by mixing FeCl3 and MgCl2. 6H2O salts in water, followed by NaOH treatment (coprecipitation method). For LDHBC, FeCl3, and MgCl2. 6H2O salts were dissolved in water, and Douglas fir biochar was added to the salts mixture to make a slurry, followed by NaOH treatment. The surface chemistry and elemental composition of both adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, and TEM. Adsorption ability of LDH and LDHBC was studied by pH effects, kinetics, and the highest capacity for the analyte

Removal of phosphate from aqueous solutions by adsorption onto Ca(OH)2 treated natural clinoptilolite

Phosphorus (P) recovery from wastewater is of great interest especially when the loaded adsorbent can be used in the agriculture as slow-release fertilizer. The application depends on environmental concerns related to the chemical modification of the adsorbent and the release of toxic compounds from the loaded material to the soil or the water during adsorption. The present work focused on the phosphate (PO4-P) removal from aqueous solutions under low P concentrations (0.5–10mg/L) by using Ca(OH)2-pretreated natural zeolite (CaT-Z). As activation agent, Ca(OH)2 presents benefits in terms of pretreatment costs and environmental impact of the applied adsorbent. The pretreatment of natural zeolite (clinoptilolite) with 0.25mol/L Ca(OH)2 led to an increase of P removal from 1.7 to 97.6% at initial P concentration of 10mg/L, pH 7 and 298K. Low residual concentrations of 81–238μg P/L were achieved at 298K rendering CaT-Z a promising sorbent for tertiary wastewater treatment. At 200mg P/L, the adsorption capacity was 7.57mg P/g CaT-Z. The P removal efficiency was pH-independent suggesting a beneficial use of CaT-Z under acidic and alkaline conditions. Adsorption was found to be an endothermic and slow process reaching equilibrium after 120h, whereas the half of the PO4-P was adsorbed in the first 8h. The applied kinetic models showed that both film and intraparticle diffusion contributed to phosphate removal. Phosphate sorption decreased in the presence of the anionic surfactant SDS, Fe2+, HCO3−, acetate and citrate anion. The predominant mechanisms of ligand exchange and Ca-P surface precipitation were confirmed by the IR-ATR and SEM-EDS analyses, respectively

Plantain peel adsorbent: Simple preparation, and adsorption at phosphate concentrations similar to those of water sources at risk of eutrophication

There are several investigations on the use of food waste to remove contaminants by adsorption. However, a simple route, without chemical activation reagents, is needed for the development of adsorbents. The aim of this study was to develop an adsorbent from plantain peel, using a simple procedure, and to evaluate its capacity to remove phosphate from aqueous solutions at phosphate concentrations similar to those of water sources at risk of eutrophication (0.30 mg/L). The simple pyrolysis method was used in an electric muffle, without chemical activation, using plantain peel as precursor. The variables evaluated were pyrolysis temperature and solution pH. The specific surface area BET, zero loading point of the developed treatments, was determined. Phosphate adsorption was studied in a batch experiment in the presence of calcium ions in solution. Phosphate adsorption was favorable at all three pyrolysis temperature levels (500, 600 and 700 °C) and two solution pH levels (pH 7 and 10). the pseudo-second order kinetic model was the best fit for the experimental data to describe the adsorption mechanism. The best fit to the experimental equilibrium data was obtained with the Langmuir isotherm model. It was found that a 1 g/L dose of the adsorbent was able to reduce 92% of phosphate in water, with a removal capacity 0.14 mg/g at pH 10 and pyrolysis temperature of 700 °C. This study lays the groundwork for future research on the use of this type of adsorbent in water treatment to facilitate access to clean water for rural populations

Isotherm and Kinetic Study of Phosphor Adsorption from Aqueous Solution using Single Wall Carbon Nanotubes

The presence of trace amounts of phosphorus in treated wastewaters from municipalities and industries results in eutrophication.Therefore, its removal is crucial for controlling eutrophication in receiving water. Hence, the aim of this study was to evaluate the phosphor adsorption from aqueous solution using single wall carbon nanotubes (SWCNT) as a sorbent. The batch experiments were performed at laboratory scale. The SWCNT was characterized using scanning electron microscope (SEM). The effects of operational parameters such as adsorbent dosage, pH, and initial phosphor concentration on initial phosphor removal were evaluated. The isotherm and kinetics of phosphor adsorption were determined. The results showed that phosphor removal was directly proportional with increase in adsorbent dosage and it was reversely proportional with increase in initial phosphorous concentration. Therefore, with adsorbent dosage increased from 0.1 to 0.4 mg/l, the percentage of removal increased from 83.0 to 92.5%. Moreover, the pseudo-first order, pseudo-second order kinetic, and intraparticle diffusion models were used to describe the kinetic data. The experimental data fitted well with pseudo-second order kinetic model. Equilibrium isotherms were analyzed by Langmuir, Freundlich, and Tempkin adsorption models. It was found that the adsorption isotherm was correlated reasonably well with Freundlich isotherm. The high adsorption capacity of SWCNT indicates that this adsorbent might be a suitable alternative to remove pollutants from aqueous media. It is concluded that the SWCNTs have a high potential for phosphor adsorption and can be used as an effective adsorption for removal of phosphor form effluents

Lignin Cationization for The Removal of Phosphates and Nitrates from Effluents of Wastewater Treatment Plants

The removal of phosphates and nitrates from wastewater treatment plant (WWTP) effluents is important for preventing pollution of receiving waters. In this study, we chemically modified alkaline lignin (aLN) with quaternary ammonium groups to obtain biodegradable cationic lignin (cLN). We characterized the cLN and tested its efficacy for removing phosphates and nitrates in a lab setting and on field-collected WWTP samples. Adsorption isotherm and kinetic studies were performed in aqueous media, and the effects of several variables (contact time, pH, initial concentration, and adsorbent dose) were investigated. The Langmuir isotherm described phosphate and nitrate adsorption well, with R2 values of 0.97 and 0.84, and maximum adsorption capacities of 0.59 mg g−1 and 2 mg g−1 respectively. For phosphate, the data fit the Freundlich isotherm model with an R2 of 0.95, suggesting that both homogenous and heterogeneous adsorbent surfaces were involved in phosphate adsorption. Adsorption kinetics revealed that both phosphate and nitrate sorption onto cLN was better described by the pseudo-second-order model, with a correlation coefficient of 1. Furthermore, a 2-dimension Doehlert matrix was used to model the effect of initial concentration and adsorbent dose on the phosphate and nitrate removal. The results showed that cLN 1516 mol% was most effective for low phosphate and nitrate concentrations. With an obtained optimum adsorbent dose of 10 mg mL−1, we achieved a successful reduction of nutrient loads of WWTP effluent from 0.42 mg L−1 to 0.18 mg L−1 (adsorption capacity of 0.6 mg g−1) and from 4.1 mg L−1 to 2.3 mg L−1 (adsorption capacity of 4.5 mg g−1), corresponding to the removal of 57.7% and 43.9% for phosphates and nitrates respectively

Hybrid ion exchange resins for phosphorus removal from wastewater.

Phosphorus is not only a non-renewable resource but also a major cause of eutrophication in natural environments. Accordingly, legislation aims to control point source discharges from wastewater treatment with new targets likely to be as low as 0.1 mg Lˉ¹. Current wastewater treatment options for phosphorus removal, based on either biological or chemical processes, are capable of meeting the new consents. However, challenges exist with both such that alternative approaches are required. One of the most promising is the use of hybrid ion exchange resins where ferric oxide nanoparticles have been embedded within the structure of the base resin. The aim of the current thesis is to understand and critically evaluate the technical and economic challenges associated with using the hybrid resin for phosphorus removal. Technical assessment demonstrates the efficacy of the resin in meeting the new standard as either a polishing process or as the main treatment unit for phosphorus removal. Elucidation of the impact of background water constituents revealed the importance of the ferric oxide nanoparticles in conjunction with targeted regeneration to enable effective removal in complex matrices. Batch experiments revealed that a combination of pseudo-second order and intra particle diffusion models can be used to model the system. The media capacity was maximum (8.5 mg gmediaˉ¹) in the first cycle and reduced to a more consistent 2.5 – 3.7 mg gmedia-1 between cycle 3 to 9. Adsorption of nitrate ions from the wastewater effluent was found to cause the most inhibition to the removal of phosphorus, followed by sulphate and then humic acid. Column trials establish the effectiveness of the process even at very low contact times of 0.5 to 1 minute. However, optimum operation was achieved around empty bed contact times of 3-5 minutes as these generate extended serviceable bed life. The media can remove phosphorus down to 0.1 mg P Lˉ¹ for treating both, full phosphorus load (at sites with no other phosphorus removal mechanism) and for phosphorus polishing (at sites where phosphorus concentration has been to reduced to ~1 mg Lˉ¹ through existing treatment). Furthermore, the resin also removed COD at a level between 40-50%, making it suitable for sites needing organic polishing. Economic analysis revealed the process offered a plausible economic alternative to standard solutions to meet low phosphorus consents. For small works (2,000 PE), HAIX fixed bed system was found to be economically competitive below empty bed contact time of 7 minutes. For medium works (20,000 PE), this increased to an empty bed contact time of 10 minutes. A mobile clean-up system for the regenerant (NaOH) has been deemed more economical for small works (2,000 PE), whereas the chemical quantity needed for medium works (20,000 PE) required an on-site clean-up system. The potential to substantially reduce total costs were identified such that confidence can be placed in the economic suitability of the solution. Importantly, the economic plausibility of the process did not require inclusion of the sale of the recovered phosphate product such that the technology is appropriate within both linear and circular economic models.STREAM EngD programm

Plantain peel adsorbent: Simple preparation, and adsorption at phosphate concentrations similar to those of water sources at risk of eutrophication

There are several investigations on the use of food waste to remove contaminants by adsorption. However, a simple route, without chemical activation reagents, is needed for the development of adsorbents. The aim of this study was to develop an adsorbent from plantain peel, using a simple procedure, and to evaluate its capacity to remove phosphate from aqueous solutions at phosphate concentrations similar to those of water sources at risk of eutrophication (0.30 mg/L). The simple pyrolysis method was used in an electric muffle, without chemical activation, using plantain peel as precursor. The variables evaluated were pyrolysis temperature and solution pH. The specific surface area BET, zero loading point of the developed treatments, was determined. Phosphate adsorption was studied in a batch experiment in the presence of calcium ions in solution. Phosphate adsorption was favorable at all three pyrolysis temperature levels (500, 600 and 700 °C) and two solution pH levels (pH 7 and 10). the pseudo-second order kinetic model was the best fit for the experimental data to describe the adsorption mechanism. The best fit to the experimental equilibrium data was obtained with the Langmuir isotherm model. It was found that a 1 g/L dose of the adsorbent was able to reduce 92% of phosphate in water, with a removal capacity 0.14 mg/g at pH 10 and pyrolysis temperature of 700 °C. This study lays the groundwork for future research on the use of this type of adsorbent in water treatment to facilitate access to clean water for rural populations