Initial Phosphate Concentration Research Articles

Role of phosphate concentration in control for phosphate removal and recovery by layered double hydroxides.

Phosphorus removal from wastewater has become urgent because of eutrophication control. Phosphate concentration in control for phosphate removal and recovery by Mg-Fe oxide has been investigated. The results show that the adsorption capacity of phosphate by Mg-Fe oxide calcined at 450°C was 28.3mg/g, and it was kept at wide optimal adsorption pH ranges (4-10). The coexisting ions had influenced phosphate adsorption process and the order is CO32- > SO42- > NO3- > Cl-, with the inhibition rate of CO32- being 43%. Interestingly, phosphate concentration plays an important role in phosphate removal by Mg-Fe oxide. Under higher initial phosphate concentrations (200-800mg/L), Sips model was well fitted. In addition, the adsorption kinetics was well described by the pseudo-second-order kinetic model before 25min and the pseudo-first-order kinetic model after 25min. In contrast, Langmuir model and pseudo-second-order kinetic model were fitted under lower initial phosphate concentrations (20-200mg/L). The results of XRD, XPS, SEM, and TEM characterization show that Mg3(PO4)2 was formed by surface precipitation under 800mg/L phosphate solution, and Mg-Fe layered structure was present via the unique memory effect under 20mg/L phosphate solution. Mg-Fe oxide can be recovered through CO32- ion exchange, and the removal efficiency of phosphate was 56% after seven cycles.

Phosphate Adsorption by Silver Nanoparticles-Loaded Activated Carbon derived from Tea Residue

This study presents the removal of phosphate from aqueous solution using a new silver nanoparticles-loaded tea activated carbon (AgNPs-TAC) material. In order to reduce costs, the tea activated carbon was produced from tea residue. Batch adsorption experiments were conducted to evaluate the effects of impregnation ratio of AgNPs and TAC, pH solution, contact time, initial phosphate concentration and dose of AgNPs-AC on removing phosphate from aqueous solution. Results show that the best conditions for phosphate adsorption occurred at the impregnation ratio AgNPs/TAC of 3% w/w, pH 3, and contact time lasting 150 min. The maximum adsorption capacity of phosphate on AgNPs-TAC determined by the Langmuir model was 13.62 mg/g at an initial phosphate concentration of 30 mg/L. The adsorption isotherm of phosphate on AgNPs-TAC fits well with both the Langmuir and Sips models. The adsorption kinetics data were also described well by the pseudo-first-order and pseudo-second-order models with high correlation coefficients of 0.978 and 0.966, respectively. The adsorption process was controlled by chemisorption through complexes and ligand exchange mechanisms. This study suggests that AgNPs-TAC is a promising, low cost adsorbent for phosphate removal from aqueous solution.

Facile synthesis of Ag/La2O2CO3 hierarchical micro/nanostructures for antibacterial activity and phosphate removal

In this study, hierarchical Ag/La2O2CO3 micro/nanostructures (MNSs) were synthesized by in situ loading Ag nanoparticles (NPs) on the surface of the La2O2CO3 MNSs. The prepared La2O2CO3 MNSs present flower-like shape and can be tuned by the molar ratio of La (NO3)3 and CO(NH2)2. In the molar ratio of 1:2 to 1:55, the La2O2CO3 MNSs mainly consist of polyhedral rods, irregular rods and irregular spindles and their size is about 10, 8 and 7 μm, respectively. After loading Ag NPs, the spindle-like Ag/La2O2CO3 MNSs were used for phosphate removal and antibacterial activity. At the initial phosphate concentration of 20 mg/L, the removal rate is 59.6%. The Ag/La2O2CO3 MNSs have significant antibacterial activity and their MIC values for S. aureus and E. coli are 31.3 and 15.6 μg/mL, respectively. The results indicate that Ag/La2O2CO3 MNSs may have good application prospects in open water to inhibit bacterial growth.

Study of microalgae (Scenedesmus Sp.) utilization as phosphate bioremediator (PO4 3−) in domestic wastewater medium

In this research, the use of Scenedesmus sp. as a phosphate bioremediator agent is expected to be applied for lowering the phosphate levels in the water as well as improving the quality of the environment. Scenedesmus sp. used in this research was isolated from Sungai Cideng. Variation of phosphates were tested to see the effect of various types of phosphate found in the waters in the form of a variation of organic phosphates using the Adenosine 5’-monophosphate (AMP), phytic acid and variation of inorganic phosphates using potassium dihydrogen phosphate (KH2PO4) and sodium tripolyphosphate (STPP). It was found that the use of monopotassium phosphate (KH2PO4) was better in decreasing phosphate levels and increasing the number of Scenedesmus sp. cells with a phosphate decrease percentage of 87.5 %. Phosphate test was performed using UV-Vis spectroscopy instrumentation and the abundance of cell count was performed using a microscope and hemocytometer. The environmental quality test parameters are temperature and pH. Direct application in wastewater from Muara Angke was also found the decrease of phosphate levels and increase the number of Scenedesmus sp. cells. Scenedesmus sp. has the ability to reduce nutrients in wastewater to below wastewater quality standard of 86.0 % from the initial phosphate concentration of 0.2255 ppm to 0.0314 ppm.

Removal of phosphate from wastewater by modified bentonite entrapped in Ca-alginate beads

Methods of removing phosphate from wastewater with a low phosphate concentration are of great environmental significance. In this study, immobilized beads were prepared by entrapping modified bentonite powder in calcium-alginate (Al-NaBT-CA), and the potential of the beads for phosphate removal from wastewater was investigated. The effects of pH (1–10) and initial phosphate concentration (0.5–50 mg/L) were also examined in batch experiments with Al-NaBT-CA beads. The optimum pH value for phosphate removal by Al-NaBT-CA beads was pH 3. In addition, a high initial phosphate concentration promoted phosphate adsorption. Adsorption kinetics showed that the adsorption of phosphate using beads followed a pseudo-second-order kinetic model (R2 = 0.98–0.99). The adsorption isotherm data was well fitted by the Sips adsorption model. The maximum phosphate adsorption capacity of the Al-NaBT-CA beads was 15.77 mg/g, which was slightly less than that of the modified powder. The specific surface area of the Al-NaBT-CA beads was 17.01 m2/g, and their average pore size was 13.41 nm. Scanning electron microscopy suggested that the high inner porosity and rough outer surface of the beads facilitated phosphate transfer.

Phosphate Limitation Increases Content of Protease Inhibitors in the Cyanobacterium Microcystis aeruginosa.

Increased anthropogenic nutrient input has led to eutrophication of lakes and ponds, resulting worldwide in more frequent and severe cyanobacterial blooms. In particular, enhanced availability of phosphorus (P) can promote cyanobacterial mass developments and may affect the content of secondary metabolites in cyanobacteria, such as protease inhibitors (PIs). PIs are common among cyanobacteria and have been shown to negatively affect herbivorous zooplankton. Here, we test the hypothesis that P-limitation reduces the growth of Microcystis, but increases the content of PIs. In batch culture experiments with eight different initial phosphate concentrations (5–75 µM) we determined growth, stoichiometry, and PI content of Microcystis aeruginosa NIVA Cya 43. This strain produces the protease inhibitor BN920 that is converted by chlorination to CP954, which constitutes the major PI in this strain. C:N:P-ratios of the biomass indicated variation of P-limitation with treatment and time. When normalized to biomass, the PI content varied up to nearly nineteen-fold with treatment and time and was highest in the low-P treatments, especially during the mid-exponential growth phase. However, these effects were alleviated under nitrogen co-limitation. The content of CP954 showed an inverse u-shaped response to growth rate and C:N-ratio of the cyanobacterial biomass, whereas it increased with cyanobacterial C:P. The results indicate that P-limitation supports a higher content of defensive PIs and may indirectly foster cyanobacterial blooms by increasing the negative interference of cyanobacteria with their consumers.

Research progress on removal of phosphate from aqueous solution by biochar and its metal modified materials

Phosphorus is the main limiting factor of eutrophication. How to control the phosphate concentration in rivers and lakes is of great significance to control eutrophication. it is considered that adsorption is an economical, efficient and simple phosphorus removal method. However, how to select the appropriate adsorption material is the key to its application. The application of biochar to the removal of phosphate from water can provide a new way for the treatment of agricultural and forestry waste, livestock manure, activated sludge and invasive plants. The phosphate-absorbing biochar can be used to improve soil improvement. Methodology is of highly advantageous but difficult in phosphate removal from practical waste water. The current paper reviewed domestic and international research results pertaining to phosphate removal by biochar. The ability of biochar to remove phosphate was summarized. The mechanism of phosphate removal by biochar or metal modified biochar was explained. The effects of pH, temperature, co-existing ion, initial phosphate concentration and other reaction conditions on the removal of phosphate by biochar were analyzed, and the characteristics of the desorption of phosphate were briefly described. Lastly, to realize the industrial application of biochar in contaminated water, it was pointed out that the mechanism of modification and phosphate removal be further researched, and experiments should be conducted using natural water bodies with complex forms of phosphorus or adsorption columns, and the research and risk assessment about phosphate-absorbing biochar as a soil amendment should be further strengthened, and the cost of biochar manufacturing should be estimated.

Synthesis of Mn/Al double oxygen biochar from dewatered sludge for enhancing phosphate removal

Abstract This study presents a simple one-step hydrothermal method to produce a new Mn/Al double oxygen sludge-derived biochar (MA-SBC) from dewatered sewage sludge, which is used for enhancing phosphate removal. Characterization results showed that a cubic spinel-type MnAl2O4 was successfully embedded in the matrix of MA-SBC. A series of systematically designed batch experiments were performed to evaluate the effect of initial pH, contact time, and initial phosphate concentration on the adsorption behavior of MA-SBC. The results revealed that the adsorption process of phosphate onto MA-SBC conformed to a pseudo-second-order model, and the rate of adsorption was mainly dominated by a mechanism of film diffusion. A Langmuir isotherm model accurately described the adsorption isotherm, with a maximum adsorption amount of 28.20 mg-P/g at 298 K (50 mg/L for the initial phosphate solution), which was more efficient than those of previously reported composites. Moreover, X-ray diffraction, Fourier transform infra-red and X-ray photoelectron spectroscopy analyses proved that the mechanism of phosphate removal from aqueous media were the inner-sphere surface complexation reaction of phosphate with ≡M-OH groups and a subsequent precipitation reaction of aluminum phosphate. Cycle stability and metallic ion leaching tests demonstrated the strong stability of MA-SBC. In general, the results of this research suggest that MA-SBC has potential applicability for removing phosphate from aqueous media as an alternative, eco-friendly, and economic adsorbent for environmental restoration.

Enhanced phosphate removal from aqueous solution using resourceable nano-CaO2/BC composite: Behaviors and mechanisms

The situation of eutrophication and shortage of phosphorus resources have triggered the development of new methods for the removal and recovery of phosphorus. In this study, a novel and highly efficient composite (nano-CaO2/BC) was fabricated by using the porous biochar (BC) to load calcium peroxide (CaO2) nanoparticles. The developed nano-CaO2/BC was applied to remove and recover phosphate from P-contained sewage. The phosphate removal performance of the composite was examined using the bulk solutions with different pH values, coexisting anions, composite dosages, and initial phosphate concentrations. The phosphate adsorption was a typical chemisorption process that agreed well with the pseudo-second-order kinetic model. Isotherm studies showed that the adsorption matched well with Langmuir-Freundlich and the maximum adsorption capacity at equilibrium was 213.22 ± 13.57 mg g−1 (298 K). The characterization results demonstrated that the predominant adsorption mechanism was precipitation. Moreover, the composite had good reusability. The seedling growth test confirmed that the P-laden composite can be mixed with soil to promote the growth of seedlings. Therefore, the method of “cycle back to soil” of used composite provided a way of resource utilization and waste disposal.

Phosphate recovery with granular acid-activated neutralized red mud: Fixed-bed column performance and breakthrough curve modelling

Granular acid-activated neutralized red mud (AaN-RM) has been successfully prepared with good chemical stability and physical strength. However, its potential for industrial application remains unknown. Therefore, the performance of granular AaN-RM for phosphate recovery in a fixed-bed column was investigated. The results demonstrated that the phosphate adsorption performance of granular AaN-RM in a fixed-bed column was affected by various operational parameters, such as the bed depth, flow rate, initial solution pH and initial phosphate concentration. With the optimal empty-bed contact time (EBCT) of 24.27 min, the number of processed bed volumes and the phosphate adsorption capacity reached 496.95 and 84.80 mg/g, respectively. Then, the saturated fixed-bed column could be effectively regenerated with a 0.5 mol/L HCl solution. The desorption efficiency remained as high as 83.45% with a low weight loss of 3.57% in the fifth regeneration cycle. In addition, breakthrough curve modelling showed that a 5-9-1 feed-forward artificial neural network (ANN) could be effectively applied for the optimization of the fixed-bed adsorption system; the coefficient of determination (R2) and the root mean square error (RMSE) evaluated on the validation-testing data were 0.9987 and 0.0183, respectively. Therefore, granular AaN-RM fixed-bed adsorption exhibits promising potential for phosphate removal and recovery from polluted water.

Impact factors on the production of β-methylamino-L-alanine (BMAA) by cyanobacteria.

Cyanobacteria produce a series of secondary metabolites, one of which is beta-N-methylamino-l-alanine (BMAA). BMAA is considered to be the cause of human neurodegeneration. Compared with other cyanotoxins, the role of BMAA in cyanobacteria remains unclear. To investigate this question, six strains of cyanobacteria were cultured and tested in this experiment with an optimized and validated BMAA determination method. The results show that four strains can produce BMAA. The effects of nutrient levels on the production of BMAA by Anabaena sp. FACHB-418 were studied by changing the initial concentrations of nitrate (NaNO3) and phosphate (K2HPO4) in mediums. Bound BMAA was detected in all samples and the concentrations were within 50-100 ng/g. Free BMAA was presence when the concentration of nitrogen was lower than 1.7 mg/L (121.43 μM). Free BMAA was released from the dead and ruptured cells during the cell decline period, so dissolved BMAA cannot be detectable in the adaptation and logarithmic periods, but could be abundant in the decline periods. Statistical analyses show that free BMAA concentrations were negatively correlated with nitrogen strongly (p = 2.334 × 10-10 and r = -0.842), but positively correlated with phosphorus weakly (p = 0.016 and r = 0.405). Moreover, the results of culture experiments indicated that exogenous BMAA could inhibit the growth of cyanobacteria that cannot produce BMAA, and the effect was enhanced as the concentration of exogenous BMAA increased. This phenomenon implies that the production of BMAA may be the stress response by some cyanobacteria to low nitrogen conditions to kill other cyanobacteria, i.e., their competitors.

Statistical optimization of lipid production by the diatom Gyrosigma sp. grown in industrial wastewater

The marine diatom Gyrosigma sp. was cultured in a medium comprised of inorganic nutrients dissolved in palm oil mill effluent (POME) wastewater. The production of lipids in the biomass was optimized using a statistical design of experiments in combination with the response surface method. The experimental factors were incident light level and initial concentrations of nitrate, phosphate, and silicate in the medium in batch culture. At 25 ± 2 °C, the maximum lipid content in the biomass harvested at the end of a 12-day batch culture was 70.7 ± 6.0% by dry weight for the following values of the experimental factors: an incident light level of 131 μmol photons m−2 s−1, a nitrate concentration of 1.8 mg L−1 (29.0 μM), a phosphate concentration of 6.8 mg L−1 (71.6 μM), and a silicate concentration of 10.1 mg L−1 (132.7 μM). Under the optimized conditions, the maximum dry mass concentration of the diatom was 560 mg L−1 on day 8 of a batch culture, declining to ~409 mg L−1 on day 12. For the 12-day batch operation, the final average productivities of the biomass and the lipids were 34.1 ± 5.5 mg L−1 day−1 and 24.1 ± 0.2 mg L−1 day−1, respectively. The fatty acids in the algal lipids were found to be as follows (%, w/w of total lipids): palmitic acid (48.6%), eicosapentaenoic acid (10.6%), myristic acid (8.1%), stearic acid (8.0%), linoleic acid (7.5%), oleic acid (6.4%), and linolenic acid (5.8%). The response surface model predicted the lipid content in the biomass with a high degree of confidence.

Fast adsorption of phosphate (PO4 -) from wastewater using glauconite.

In this study, the removal of phosphate (PO4 -) from wastewater using glauconite was investigated. Glauconite was characterized by N2 adsorption-desorption isotherm, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and Fourier transform infrared (FTIR) spectroscopy. The effects of contact time, pH, initial phosphate concentrations, adsorbent dose, and temperature were investigated by batch experiments. The isotherms, kinetics and thermodynamics for phosphate removal were studied. The results showed that glauconite had a rough surface and abundant pores. The determined Brunauer-Emmett-Teller (BET) surface area was 55 m2/g with a pore radius of 1.99 nm and the pore volume was 0.032 cm3/g. FTIR analysis revealed that the abundance of various functional groups on the surface of glauconite may play an important role for the adsorption process. The optimum pH was 11 with complete removal of phosphate in a short time (nearly 1 min). The experimental data fitted very well with the Langmuir isotherm (R2 = 0.999) with a maximum adsorption capacity of 32.26 mg/g at 50 °C. Adsorption kinetic data were best fitted with the pseudo-second-order kinetic model (R2 = 0.999). Thermodynamic study confirmed the spontaneous, endothermic and irreversible adsorption process. Therefore, glauconite is a promising natural low-cost adsorbent for phosphate removal from wastewater.

Wastewater treatment valorisation by simultaneously removing and recovering phosphate and ammonia from municipal effluents using a mechano-thermo activated magnesite technology

Phosphate and nitrate enrichment largely impair aquatic ecosystem functions and services, thus comprising an emerging problem of environmental concern. The problem pertains to developing countries where their discharge to surface water is on the rise due to a rapid growth in population. Herein, these pollutants (phosphate and ammonia) were removed from real municipal wastewater using a simple, fast, and cost-effective process. Raw cryptocrystalline magnesite, a mineral abundant in South Africa, was simply milled and calcined (mechano-thermo processing) in order to produce the activated magnesite (feed). The feed was then used in batch processing for pollutants adsorption and precipitation from real wastewater. The process was optimised by varying the treatment or contact time, feed dosage, concentration, pH, and temperature. The feed and product mineral (produced sludge) were characterised using X-ray Diffraction (XRD), field emission scanning electron microscopy (FESEM) compatible with energy dispersive spectroscopy (EDS), and Fourier Transform Infrared Spectrometer (FTIR). It was identified that the optimal conditions differed for each pollutant, highlighting the importance of tailoring the process to fit the local wastewater characteristics and as part of a treatment train system. Specifically, maximum P removal was achieved after 5 min of mixing, using 1 g L−1 of feed, 123 mg L−1 initial phosphate concentration, pH 8 – 10, and was not affected by temperature variations; whereas, for ammonia removal, optimal conditions were 180 min, 16 g L−1 feed dosage, 80 mg L−1 initial concentration, pH 10 and temperature > 45 °C. The optimal conditions for the removal of both pollutants from real wastewater were 30 min, 6 g L−1 dosage, and ambient temperature and pH. Furthermore, Mg and Ca concentration was found to influence the process. Reduction in total dissolved solids (TDS) and electrical conductivity (EC) suggest an attenuation of chemical species. Characterisation revealed that the product mineral obtained under the optimal conditions for pollutants removal is rich in quartz, periclase, brucite, calcite, magnesite, and struvite. This was further supported by the FTIR results, which indicated the presence of Mg–O, PO43−, N–H and OH stretches. In addition, the EDS verified the presence of Mg, Ca and P in product mineral. Results are suggestive of the high efficiency of the mechano-thermo activated magnesite treatment process for phosphate and ammonia removal and struvite crystallization. Thus, this technology could valorise municipal wastewater effluents and open new horizons for the effective and sustainable management of wastewater effluents, since struvite can replace the mined phosphate fertilizers, which are rapidly depleting, in the agriculture industry.

Removal of phosphate from aqueous solution using MgO-modified magnetic biochar derived from anaerobic digestion residue

A novel MgO-modified magnetic biochar (MgO@MBC) was made by chemical co-precipitation of Mg2+/Fe3+ on anaerobic digestion residue (ADR) and subsequently pyrolyzing at different temperatures. MgO@MBC was used for phosphate recovery from aqueous solution. The physicochemical properties of MgO@MBC were comprehensively investigated using TEM-EDS, FT-IR, XRD, VSM, N2 adsorption-desorption and TGA. Results showed that MgO/γ-Fe2O3 nanoparticles were successfully deposited onto the surface of BC. The effects of reaction temperature, initial solution pH, MgO@MBC dosage, coexisting anions and phosphate concentration on the removal of phosphate by MgO@MBC were researched. Additionally, the adsorption process of phosphate onto MgO@MBC was well described by the pseudo second-order and pseudo first-order models, which indicated a chemisorption and physisorption process. Besides, the maximum adsorption capacity of MgO@MBC for phosphate by the Langmuir model were 149.25 mg/g at 25 °C. Moreover, the thermodynamic study suggested that the adsorption of phosphate onto MgO@MBC was a spontaneous and endothermic process. The adsorption mechanisms including physical absorption, surface electrostatic attraction, surface complexation and precipitation were revealed. It could be concluded that MgO@MBC exhibited high removal efficiency of phosphate and excellent magnetic property for the recovery. MgO@MBC could be utilized as a magnetically recoverable adsorbent to realize phosphate recovery and MgO@MBC after the adsorpion of phosphate could be applied in agricultural production as a fertilizer.

Phosphorus recovery from wastewater using light calcined magnesite, effects of alkalinity and organic acids

To solve the problem of phosphorus pollution and resource crisis, phosphorus recovery by struvite crystallization has become a focus of research in recent years. In municipal wastewater, insufficient magnesium content and relatively low pH can be a limitation for struvite formation. A commercial magnesium source, light calcined magnesite (LCM), was used in this study for phosphorus recovery from wastewater without an adjustment of pH. Bench-scale jar test experiments were conducted to study the kinetics of phosphate removal by LCM. The effects of LCM dosage, initial phosphate concentration, carbonate alkalinity and organic acid content on the removal of phosphate was evaluated. Hydrolyzation of LCM released hydroxyl ions (OH−) during the reaction, increasing the solution pH from 7.63 to 8.62. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the composition and morphology of formed precipitates. At an LCM dosage of 200 mg/L, 84.5% of phosphate was removed mainly through the formation of struvite. Increased alkalinity and organic acid concentration in the solution inhibited struvite formation, and higher alkalinity promoted the formation of coarse crystal surfaces. Abundant global reserves of the magnesite ore resource reveal LCM may be a viable and cost-effective source of magnesium and hydroxyl reagent for phosphorus recovery from wastewater.

Electrochemical removal of phosphate from synthetic effluent: A comparative study between iron and aluminum by using experimental design methodology

In this work, the removal of orthophosphate from synthetic wastewaters is studied by the electrocoagulation (EC) process using respectively aluminum and iron electrodes connected in monopolar configuration. The effects of current intensity, initial phosphate concentration, initial solution pH, treatment time and electrode type were investigated by experimental design methodology (EDM). The factorial design (FD) used in the first time shows that the current intensity and the electrolysis time have a positive effect on the orthophosphate removal rate while the pH and the initial concentration have a negative effect on it. Using Aluminum electrode, phosphate removal rate were higher than those recorded with iron electrode. A central composite design (CCD) was then used to optimize the removal rate while minimizing the mass of sludge produced. The optimal conditions obtained are the following: for aluminum electrodes (intensity 1.09A, concentration 48.55mg / L, pH 4 and time 59.19min) and for iron electrodes (Intensity 0.85A, concentration 26.8mg/L, pH 3 and time 47.48min). Under these conditions, 99.33% (48.21mg/L) of phosphate was removed by using aluminum electrode with metallic residues of 2.1g. By comparison, 80.74% (21.63mg/L) of phosphate was removed using iron electrode with metallic sludge residues generated of 1.01g.

Kinetics, thermodynamics and mechanisms of phosphate sorption onto bottle gourd biomass modified by (3-chloro-2-hydroxypropyl) trimethylammonium chloride

The sorption kinetics and thermodynamic parameters of phosphate removal from aqueous solution using quaternary ammonium–modified bottle gourd biomass as a sorbent were studied in a batch reactor. The cationic sorbent, containing trimethylammonium and hydroxypropyl groups, was obtained through the chemical reactions of the lignocellulosic Lagenaria vulgaris shell with (3-chloro-2-hydroxypropyl)trimethylammonium chloride. Experimental data of phosphate sorption from aqueous solutions of different initial concentrations (5–140 mg P L−1) have been analysed by reaction kinetics and diffusion models. The characteristic rate constants calculated by linear and non-linear regression analyses of the experimental results are presented. The phosphate sorption reaches equilibrium in 20–30 min, depending on the initial phosphate concentration. The maximum sorption capacity of quaternary ammonium–modified bottle gourd (QABG) sorbent was 18 mg P g−1at 20 oC. The sorption system is best described by a non-linear equation of the pseudo first-order model ( R2 > 0.996). The Weber–Morris model indicated that the sorption process took place in three steps, whereby the intra-particle diffusion is not the only rate-controlling step. In addition, the effect of temperature (20 oC–50 oC) on sorption kinetics was also investigated. The various thermodynamic parameters suggest that phosphate sorption is favoured and is an exothermic process. The activation energy and the sticking probability confirmed that anion exchange is the dominant mechanism. These results provide valuable information for the potential use of agricultural residues in the treatment of wastewaters.

Optimization of photo fermentation in corn stalk through phosphate additive

Phosphorus is an essential nutrient for microbial growth which effectively influences the bio‑hydrogen production process. In the present study, the effect of phosphate concentration on simultaneous saccharification fermentation (SSF) hydrogen production by phototrophic microbial consortium has been investigated at various initial pH conditions (6, 7 and 8). The experimental results show that the hydrogen yield has been improved through the addition of phosphate, depending on initial pH and phosphate concentration. The maximum hydrogen yield of 63.09 ± 0.38 mL/g TS and highest energy conversion efficiency of 4.14 ± 0.02% from raw corn stalk were achieved at the phosphate concentration of 4 mmol/L with initial pH value of 6. We have shown that hydrogen yield for raw corn stalk can be enhanced by selecting appropriate amount of the additive. These results may help in optimization of the hydrogen production yield at industrial scale.

Removal of phosphate by Donnan dialysis coupled with adsorption onto calcium alginate beads.

In this study the removal of phosphates from solution by Donnan dialysis and by adsorption onto calcium alginate beads were studied separately and then together. This hybrid process was conducted in order to benefit from each process, and it is an original and new combination. First, the Donnan dialysis process was performed with different parameters: the type of counter-ion, the concentration of the counter-ion, the initial phosphate concentration, the pH of the solution and the choice of anion-exchange membranes. Donnan dialysis achieved 68% and 12.5% phosphorus removal with AMX and AFN membranes respectively. Then a preliminary study into the adsorption of phosphate onto calcium alginate beads was carried out. A full factor design was applied in order to determine the effect of the main parameters and their mutual interactions for the adsorption process. The removal of phosphate onto calcium alginate beads reached 82.5%. Finally, coupling Donnan dialysis with adsorption onto calcium alginate beads for the removal of phosphate reached 89.5% with the AMX membrane. This hybrid process can be considered to be a solution for improving the contact time and for enhancing the removal of phosphate by 10% compared to adsorption onto calcium alginate.