Optimization of phosphate recovery from urine by layered double hydroxides

Efficient phosphate removal by Mg-La binary layered double hydroxides: synthesis optimization, adsorption performance, and inner mechanism

Layered double hydroxides (LDH) hold great promise as phosphate adsorbents; however, the conventional binary LDH exhibits low adsorption rate and adsorption capacity. In this study, Mg and La were chosen as binary metals in the synthesis of Mg-La LDH to enhance phosphate efficient adsorption. Different molar ratios of Mg to La (2:1, 3:1, and 4:1) were investigated to further enhance P adsorption. The best performing Mg-La LDH, with Mg to La ratio is 4:1 (LDH-4), presented a larger adsorption capacity and faster adsorption rate than other Mg-La LDH. The maximum adsorption capacity (87.23 mg/g) and the rapid adsorption rate in the initial 25 min of LDH-4 (70 mg/(g·h)) were at least 1.6 times and 1.8 times higher than the others. The kinetics, isotherms, the effect of initial pH and co-existing anions, and the adsorption-desorption cycle experiment were studied. The batch experiment results proved that the chemisorption progress occurred on the single-layered LDH surface and the optimized LDH exhibited strong anti-interference capability. Furthermore, the structural characteristics and adsorption mechanism were further investigated by SEM, BET, FTIR, XRD, and XPS. The characterization results showed that the different metal ratios could lead to changes in the metal hydroxide layer and the main ions inside. At lower Mg/La ratios, distortion occurred in the hydroxide layer, resulting in lower crystallinity and lower performance. The characterization results also proved that the main mechanisms of phosphate adsorption are electrostatic adsorption, ion exchange, and inner-sphere complexation. The results emphasized that the Mg-La LDH was efficient in phosphate removal and could be successfully used for this purpose.

Phosphate Recovery from Urine-Equivalent Solutions for Fertilizer Production for Plant Growth

This study presents a proof of concept for the recovery of phosphate from aqueous solutions with high phosphorus (PO4-P) initial contents to simulate the concentration of streams from decentralized wastewater systems. Solutions with ∼500 ppm phosphorus enable phosphate adsorption and recovery, in contrast to the highly diluted inlet streams (<10 ppm) from centralized wastewater treatment plants. In this work, Mg-Fe layered double hydroxide is used as a phosphate adsorbent, demonstrating its separation from aqueous streams, recovery, and use as a fertilizer following the principles of circular economy. We demonstrate that the mechanism of phosphate adsorption in this material is by a combination of surface complexation and electrostatic attraction. After the loss of crystallinity in the presence of water in the first cycle and its associated decrease in adsorption capacity, the Mg-Fe layered double hydroxide (LDH) is stable after consecutive adsorption/desorption cycles, where desorption solutions were reused to substantially increase the final phosphate concentration demonstrating the recyclability of the material in a semicontinuous process. Phosphate recovered in this way was used to complement phosphate-deficient plant growth medium, demonstrating its efficacy as a fertilizer and thereby promoting a circular and sustainable economy.

Ca-La layered double hydroxide (LDH) for selective and efficient removal of phosphate from wastewater

Adsorption showed advantages in removing phosphorus (P) at low concentrations. Desirable adsorbents should have sufficiently high adsorption capacity and selectivity. In this study, a Ca-La layered double hydroxide (LDH) was synthesized for the first time by using a simple hydrothermal coprecipitation method for phosphate removal from wastewater. A maximum adsorption capacity of 194.04 mgP/g was achieved, ranking on the top of known LDHs. Adsorption kinetic experiments showed that 0.02 g/L Ca-La LDH could effectively reduce PO₄^3-P from 1.0 to <0.02 mg/L within 30 min. With the copresence of bicarbonate and sulfate at concentrations 17.1 and 35.7 times of that of PO₄^3-P, the Ca-La LDH showed promising selectivity towards phosphate (with a reduction in the adsorption capacity of <13.6%). In addition, four other (Mg-La, Co-La, Ni-La, and Cu-La) LDHs containing different divalent metal ions were synthesized by using the same coprecipitation method. Results showed much higher P adsorption performance of the Ca-La LDH than those LDHs. Field Emission Electron Microscopy (FE-SEM)-Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and mesoporous analysis were performed to characterize and compare the adsorption mechanisms of different LDHs. The high adsorption capacity and selectivity of the Ca-La LDH were mainly explained by selective chemical adsorption, ion exchange, and inner sphere complexation.

Starch modified NiFe layered double hydroxide composites for better adsorption and photocatalytic removal of reactive dye and piroxicam-20 drug

One of the most omnipresent problems to the environment is the efficient removal of textile dyes and non-steroidal drugs from wastewater. For this purpose, renewable, sustainable, and biodegradable biopolymers are used. In this study, starch (S) modified NiFe-layered double hydroxide (LDH) composites were successfully synthesized by the co-precipitation method and have been examined as a catalyst for the effective adsorption of reactive blue 19 dye, reactive orange 16 dye, and piroxicam-20 NSAID from wastewater and photocatalytic degradation of reactive red 120 dye. The physicochemical properties of the prepared catalyst were assessed by XRD, FTIR, HRTEM, FE-SEM, DLS, ZETA, and BET. The coarser and more porous micrographs are shown in FESEM, indicating the homogeneous dispersion of layered double hydroxide on starch polymer chains. The S/NiFe-LDH composites have a slightly greater S_BET (6.736 m²/g) than NiFe LDH (4.78 m²/g). The S/NiFe-LDH composite shows remarkable ability in the removal of reactive dyes. The band gap value of NiFe LDH, S/NiFe LDH (0.5:1), and S/NiFe LDH (1:1) composites was calculated as 2.28 eV, 1.80 eV, and 1.74 eV, respectively. The q_max assessed from Langmuir isotherm for removal of piroxicam-20 drug, reactive blue 19 dye, and reactive orange 16 was 2840 mg/g, 149.47 mg/g, and 182.4 mg/g, respectively. The activated chemical adsorption without product desorption is predicted by the Elovich kinetic model. With reactive red 120 dye, S/NiFe-LDH shows photocatalytic degradation within 3 h of irradiation of visible light with 90% removal efficiency and follows a pseudo-first-order kinetic model. The scavenging experiment confirms the involvement of electrons and holes in photocatalytic degradation. With a little decline in adsorption capacity up to five cycles, starch/NiFe LDH was easily regenerated. So, the suitable adsorbent required for wastewater treatment is nanocomposites of LDHs and starch as they enhance the chemical and physical attributes of the composite structure with greater absorption capabilities.

Mechanistic insights into the selective adsorption of phosphorus from wastewater by MgO(100)-functionalized cellulose sponge

Metal oxides have remained state-of-the-art adsorbents for recovering phosphorus from aqueous solutions, but their practical application is still limited by their unsatisfactory adsorption capacities and selectivities in wastewater. Here, using MgO as a model metal oxide, the strategy of employing porous cellulose sponge to support metal oxides featuring exposed specific crystal facets was proposed to develop promising phosphate adsorbents. The phosphate adsorption isotherms and kinetics were measured and the phosphate adsorption mechanism was explored. The results show that cellulose sponge-supported MgO(100) (C-MgO(100)) has a saturation capacity of 28.3 mg P/g, over ten times higher than MgO(100) particles. Importantly, the phosphate adsorption properties of C-MgO(100) are almost not affected in wastewater, demonstrating its exceptional selectivity for phosphate adsorption. In contrast, the saturation capacity of MgO(111)-functionalized cellulose sponge is obviously declined in wastewater. Experimental together with theoretical analyses indicate that phosphate is chemically adsorbed on C-MgO(100) with obvious electrons transfer from the p-orbital of phosphate, and the adsorption energy of C-MgO(100) towards phosphate is maintained in the presence of coexisting anions. Ultimately, regeneration experiments reveal that a regenerant formulation composed of KOH (wt.1 %) and tap water is suitable for the regeneration of C-MgO(100) with >82.6 % phosphate desorption efficiencies after 5 cycles, further confirming its potential in practical application for the treatment of real water.

Simultaneous removal of phosphate and antibiotic from hydrolyzed urine by novel spherical particles

Phosphate recovery from wastewater is regarded as promising strategy to achieve sustainable supply of non-renewable natural resources. In this study, a novel technique for spherical materials preparation was developed to achieve both phosphate recovery and antibiotic removal from urine. Phosphate removal and sulfamethoxazole (SMX) degradation performance of the synthesized spherical materials was studied in synthesized urine and real urine. MgB, made from magnesium oxide (10%) and biochar (10%), was the most effective in phosphate removal and SMX degradation. Struvite formation and radical production were the mechanisms of phosphate removal and SMX degradation, respectively. The phosphate removal capacity of MgB was 0.181 g/g and the removal cost was around 0.245 RMB/g phosphate. Meanwhile, the combination of MgB and persulfate could achieve a 98% degradation efficiency of SMX, which could eliminate the hazardous impurity in final product. Furthermore, this technique has also been validated useful in treating real hydrolyzed urine.

Selective adsorption of anions on hydrotalcite-like compounds derived from drinking water treatment residuals

Most drinking water treatment residuals (DWTRs) with rich metal resources are landfilled directly without treatment, which results in wasted Al/Fe resources. This work proposes a new method of preparing Mg-Al-Fe Hydrotalcite-like compounds (MAF-HTCLs) by recycling DWTRs as the raw material to selectively adsorb anions in the waste water. In this study, MAF-HTCLs were prepared by the coprecipitation method with recycled DWTRs. The characterizations and adsorption of MAF-HTCLs were studied for the selective adsorption of P, Cr, F, and Br. The adsorption capacity was increasing as the value of pH decreased. For kinetic adsorption, the pseudo-second-order model fit better, and two isotherm models (the Langmuir and Freundlich models) described the isotherm results well. According to the Langmuir model, the maximum adsorption capacities of P, Cr, F, and Br were 55.2, 34.9, 16.84, and 13.9 mg/g, respectively. Based on the results of characterizations before and after adsorption, adsorption mechanisms of Cr, F, and Br were proposed, including physicochemical adsorption, surface complexation, and ion exchange, in which ion exchange was dominant. Finally, we determined that the selective adsorption mechanisms of P on MAF-HTCLs included strong ion exchange and surface chemical precipitation by analyzing the results of X-ray photoelectron spectroscopy.

Superior residual fertiliser value in soil with phosphorus recycled from urine in layered double hydroxides

Layered double hydroxides (LDHs) of magnesium (Mg) and aluminium (Al) are ion exchangers that can be used as slow release phosphorus (P) fertilisers. These LDHs can be used successfully to concentrate P from waste streams such as urine. This study was set up to test the fertiliser potential of P derived from urine and concentrated on LDHs. Ryegrass was grown in a pot trial using a P- and N-deficient soil where different urine derived fertilisers, i.e. LDH-P, stored urine and urine mixed with sludge as a source of P were compared to different mineral N and P doses in a full factorial design. Plants were grown for 75 days with four cuttings and did not exhibit salinity stress in stored urine treatments. Plant growth and P uptake responded to N, P doses in mineral fertilizer treatments with significant N-P interaction. The fertiliser use efficiency of urine fertilisers was lower than that of mineral fertilisers at equivalent total nutrient input for stored urine, due to lower N availability, and for urine mixed with sludge due to lower P availability. In contrast, the yield and P uptake of ryegrass grown on LDH loaded with P from urine (LDH-P) showed equal fertiliser P use as mineral fertiliser. Interestingly, the residual soil P after harvest, scored by the sum of isotopically exchangeable P in soil and the P uptake, was higher for LDH-P than for mineral P, confirming slow release properties of LDH that limit loss of P by fixation in soil.

Rare earth elements (REE) for the removal and recovery of phosphorus: A review

There is little doubt that 'rock phosphate' reserves are decreasing, with phosphorus (P) peak to be reached in the coming decades. Hence, removal and recovery of phosphorus (P) from alternative nutrient-rich waste streams is critical and of great importance owing to its essential role in agricultural productivity. Adsorption technique is efficient, cost-effective, and sustainable for P recovery from waste streams which otherwise can cause eutrophication in receiving waters. As selective P sorption using rare earth elements (REE) are gaining considerable attention, this review extensively focuses on P recovery by utilising a range of REE-incorporated adsorbents. The review briefly provides existing knowledge of P in various waste streams, and examines the chemistry and behaviour of REE in soil and water in detail. The impact of interfering ions on P removal using REE, adsorbent regeneration for reuse, and life cycle assessment of REE are further explored. While it is clear that REE-sorbents have excellent potential to recover P from wastewaters and to be used as fertilisers, there are gaps to be addressed. Future studies should target recovery and reuse of REE as P fertilisers using real wastewaters. More field trials of synthesized REE-sorbents are highly recommended before practical application.

State of the art of urine treatment technologies: A critical review

Over the last 15 years, urine treatment technologies have developed from lab studies of a few pioneers to an interesting innovation, attracting attention from a growing number of process engineers. In this broad review, we present literature from more than a decade on biological, physical-chemical and electrochemical urine treatment processes. Like in the first review on urine treatment from 2006, we categorize the technologies according to the following objectives: stabilization, volume reduction, targeted N-recovery, targeted P-recovery, nutrient removal, sanitization, and handling of organic micropollutants. We add energy recovery as a new objective, because extensive work has been done on electrochemical energy harvesting, especially with bio-electrochemical systems. Our review reveals that biological processes are a good choice for urine stabilization. They have the advantage of little demand for chemicals and energy. Due to instabilities, however, they are not suited for bathroom applications and they cannot provide the desired volume reduction on their own. A number of physical-chemical treatment technologies are applicable at bathroom scale and can provide the necessary volume reduction, but only with a steady supply of chemicals and often with high demand for energy and maintenance. Electrochemical processes is a recent, but rapidly growing field, which could give rise to exciting technologies at bathroom scale, although energy production might only be interesting for niche applications. The review includes a qualitative assessment of all unit processes. A quantitative comparison of treatment performance was not the goal of the study and could anyway only be done for complete treatment trains. An important next step in urine technology research and development will be the combination of unit processes to set up and test robust treatment trains. We hope that the present review will help guide these efforts to accelerate the development towards a mature technology with pilot scale and eventually full-scale implementations.

Advanced treatment of phosphorus-containing tail water by Fe-Mg-Zr layered double hydroxide beads: Performance and mechanism

The adsorption process for low concentration phosphorus wastewater treatment has advantages of simple convenience, stable performance and less sludge, while most of current adsorbents fail to be separated for reuse. Meanwhile, few people pay attention to the removal of low concentration phosphorus from tail water by adsorbents. In this study, a newly efficient Fe-Mg-Zr layered double hydroxide beads were prepared by simple in-situ crosslinking method and applied for low concentration phosphorus adsorption from real tail water. The maximum adsorption capacity of Fe-Mg-Zr beads was 21.61 mg/g, showing more practical application value for phosphorus removal. Fixed bed experiments showed that 5.0 g adsorbent could removed 2.12 mg phosphorus from tail wastewater containing 1.03 mg/L phosphorus. The beads adsorbent can be reused with excellent adsorption performance even after five cycles of adsorption-desorption operation. After detailed analyses, it was found that ligand exchange and ion exchange were the dominant mechanisms for phosphorus adsorption by this beads. Overall, the material has the advantages of simple preparation, good adsorption performance, easy separation and recycle, indicating a great potential for low concentration phosphorus wastewater treatment.

Novel sorbent shows promising financial results on P recovery from sludge water

For several decades, researchers have been struggling to obtain minimum phosphorus (P) capture costs to meet the parameters for discharging wastewater into the watercourse. Findings from ongoing practices suggest that the Modified University of Cape Town process is currently the cheapest P capture method in the USA, whereas struvite precipitation seems to be the most cost effective method in the rest of the developed world. P sorption via biochars is becoming widespread in developing countries because this technique allows for the turning of voluminous biowaste into fertilizer with soil improving properties. Nevertheless, the reliability of this technology fluctuates throughout the year according to biowaste characteristics. For the first time, it has been proposed to use broken cellulose casings, which are readily available in increasing quantities worldwide. The sorbent obtained was subsequently activated by calcium chloride (CaCl₂), whose cost is irrelevant as it would be used for agronomical purposes anyway. Pilot scale experiments show that this novel sorbent is capable of capturing 31.8 kg P t^-1 from sludge water that contains 52.5 mg of extractable P L^-1. More importantly, it was reported that the novel sorbent captures P, mostly in calcium phosphates (CaP) forms (191.5 g CaP t^-1), which are the most valuable for plant nutrition. Enough evidence was obtained to claim that the ongoing technological race to meet the P discharge standards at the lowest cost possible should also reflect the agronomic value of P to plant nutrition to increase its competitiveness.

Adsorption of phosphate on iron-coated sand granules as a robust end-of-pipe purification strategy in the horticulture sector

Nutrient enrichment in water bodies, and its detrimental consequences, are a well known and worldwide environmental problem. Agricultural activities are identified as an important source of diffuse losses of phosphate and nitrate because of the leaching out fertilizers from agricultural fields. This study encompasses the implementation of an end-of-pipe treatment by capturing phosphate from greenhouse effluent, using granular iron-coated sand (ICS) in an adsorption process. ICS is evaluated as a low-cost by-product because of its adsorption capacity and kinetics. The Langmuir isotherm was suitable for describing the adsorption thermodynamics. The adsorption capacity at an equilibrium concentration C_e of 25 mg PO₄-P/L ranged between 1.85 and 3.07 mg PO₄-P/g sorbent. Furthermore, both the pseudo-second-order model (R² = 0.9823) and the Elovich model (R² = 0.9803) showed a good fit with the kinetic data over the time range investigated, indicating that chemisorption is the rate-limiting step controlling the adsorption process. Higher adsorption capacities were observed at lower initial pH. Continuous bench-scale column experiments were performed to verify the adsorption potential of a filter bed under flow-through conditions, and the experimental data were fit to the Bohart-Adams model. Additionally, a discontinuous feeding regime of the column, resulting in intermediate resting periods, was introduced and showed an enhanced adsorption efficiency over a longer period. Finally, a pilot-scale experiment showed the potential of the ICS for the removal of phosphate from greenhouse effluent. The adsorption process, moreover, enables the recovery of phosphate via efficient desorption.

Granulation and calcination of alum sludge for the development of a phosphorus adsorbent: From lab scale to pilot scale

Alum sludge, an Al-oxyhydroxide rich waste product from water treatment practices, has the potential to be valorized as a P adsorbent material. However, several challenges currently prevent its application as an adsorbent in industrial setting, i.e. a limited P adsorption capacity due to saturation by organic matter and a fine nature resulting in percolation problems in adsorption bed setups. In this study, granulation and subsequent calcination of alum sludge were proposed to overcome these issues and to improve the P adsorption properties of alum-based adsorbent (ABA) materials. The effect of calcination temperature on the physicochemical properties of granular material was examined using X-ray diffraction, mass-spectroscopy coupled thermogravimetric analysis, Fourier-transform infrared spectrometry and specific surface area analysis, combined with density and crushing strength measurements. The ABA material obtained at 550 °C showed superior P adsorption properties and, therefore, this material was selected for further P adsorption testing and characterization (scanning electron microscopy and sieving). Batch P adsorption tests showed that this material had a maximum P adsorption capacity of 7.27 mg-P g^-1. Kinetic adsorption tests determined the effect of the solid-to-liquid ratio and the granule particle size on the P removal. Finally, the performance of the ABA-550 material was tested in a pilot-scale adsorption setup, using a surface water stream (0.47 mg-P L^-1) at a flow rate of 200 L h^-1. During the test, the P removal efficiency always exceeded 86%, while the material maintained its structural stability. The results of this study illustrate the potential of granulated/calcined ABA materials for P adsorption, paving the way for the industrial application of this novel, sustainable P removal technology.

Starch-Mg/Al layered double hydroxide composites as an efficient solid phase extraction sorbent for non-steroidal anti-inflammatory drugs as environmental pollutants

Using a co-precipitation method, starch-Mg/Al layered double hydroxide (S-Mg/Al LDH) composites were synthesized. Their physicochemical properties were assessed by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermo-gravimetric analysis. The quantification of six non-steroidal anti-inflammatory drugs (NSAIDs) was conducted using real samples (e.g., hospital waste water, river water, sewage treatment plant water, and tablet formulations) by gas chromatography-mass spectrometry. For the development of this method, the system was optimized in terms of several key variables (e.g., pH, flow rate, and eluent type/volume). The developed method for NSAIDs exhibited good resolution, sensitivity, reproducibility, and specificity even in complex matrices with limits of detection between 4 and 20 pg/mL. Hence, S-Mg/Al LDH composites were proven to be efficient and fast solid phase extraction (SPE) sorbents for NSAIDs. In addition, each LDH-SPE cartridge showed good reusability without a noticeable change in performance (e.g., up to 30 cycles) and target recoveries between 99.5 - 82.9 %. This work should open up new opportunities for a sesnsitive and sustainable quantitative method for the determination of NSAIDs in complex samples.

Lanthanum molybdate/magnetite for selective phosphate removal from wastewater: characterization, performance, and sorption mechanisms

Lanthanum molybdate/magnetite (M-La₂(MoO₄)₃) with various LaCl₃/Fe₃O₄ mass ratios was synthesized and optimized for selective phosphate removal from wastewater. M-La₂(MoO₄)₃ (2:1) was selected on the basis of phosphate sorption capacity for further experiments and characterized by a variety of methods. The phosphate sorption kinetics, isotherms, and matrix effect were studied. The maximum sorption capacity at initial pH 7 indicates the possible applicability M-La₂(MoO₄)₃ (2:1) in removing phosphate from the aquatic environment. Phosphate removal by M-La₂(MoO₄)₃ (2:1) with high selectivity was achieved in the presence of other co-existing anions, while calcium and magnesium ions were found to inhibit the sorption process. The sorption isotherm study showed that Freundlich and Sips models fit better the Langmuir model, indicating that heterogeneous multilayer sorption was dominant during the phosphate sorption process. Sorption kinetic results showed that the pseudo-first-order kinetic model can describe well the phosphate sorption process by M-La₂(MoO₄)₃ (2:1). Consecutive sorption-desorption runs showed that M-La₂(MoO₄)₃ (2:1) could be reused for a few cycles. Simultaneous removal of phosphate and organic matter was achieved in real wastewater by using M-La₂(MoO₄)₃ (2:1). The sorption mechanism was inner-sphere complexation.

Stability of magnetic LDH composites used for phosphate recovery

Layered double hydroxides (LDH) and their magnetic composites have been intensively investigated as recyclable high-capacity phosphate sorbents but with little attention to their stability as function of pH and phosphate concentration. The stability of a Fe₃O₄@SiO₂-Mg₃Fe LDH P sorbent as function of pH (5-11) and orthophosphate (P_i) concentration (1-300 mg P/L) was investigated. The composite has high adsorption capacity (approx. 80 mg P/g) at pH 5 but with fast dissolution of the LDH component resulting in formation of ferrihydrite as evidenced by Mössbauer spectroscopy. At pH 7 more than 60% of the LDH dissolves within 60 min, while at alkaline pH, the LDH is more stable but with less than 40% adsorption capacity as compared to pH 5. The high P_i sorption at acid to neutral pH is attributed to P_i bonding to the residual ferrihydrite. Under alkaline conditions P_i is sorbed to LDH at low P_i concentration while magnesium phosphates form at higher P_i concentration evidenced by solid-state ³¹P MAS NMR, powder X-ray diffraction and chemical analyses. Sorption as function of pH and P_i concentration has been fitted by a Rational 2D function allowing for estimation of P_i sorption and precipitation. In conclusion, the instability of the LDH component limits its application in wastewater treatment from acid to alkaline pH. Future use of magnetic LDH composites requires substantial stabilisation of the LDH component.

Phosphorus hyperaccumulation in nano-MgO using a circular recovery process based on multiple phase transitions from periclase to brucite

Phosphorus recovery from water is not only necessary for the protection of aquatic environments but also to meet the needs of sustainable development. We find that the adsorption capacity of nano-MgO is far from being fully utilized because of its simultaneous hydration into brucite. Annealing is a useful method of recovering its adsorption capacity without the need for desorption. Phosphate can be accumulated to a much higher level, even surpassing its theoretical equilibrium adsorption limit, so that high-quality fertilizer can be obtained (115.9 mg-P/g-MgO). Phosphate ions exist as HPO₄^2- and PO₄^3- in the sorbent during its phase transition from periclase to brucite, which is the main reason for its extremely high and reactivatable phosphorus recovery properties. This finding not only provides a new efficient phosphorous recovery strategy but will also lead to new understandings of traditional reactive nano-sorbents.

Environment-Friendly Approach toward the Treatment of Raw Agricultural Wastewater and River Water via Flocculation Using Chitosan and Bean Straw Flour as Bioflocculants

Currently, there is a growing concern regarding water remediation from agricultural and domestic wastewaters. Among water treatment methods, flocculation is a widely used approach. In this study, the bioflocculation of wastewaters from Sinaloa (Mexico) was examined using two bioflocculants: chitosan and bean straw flour (BSF). The jar-test results showed that chitosan exhibited high effectiveness in pollutant removal from different sampling zones (agricultural wastewater and river water). Additionally, this bioflocculant reduced remarkably the concentration of Mn and Fe. On the other hand, BSF showed high effectiveness in pollutant removal for a specific type of wastewater, being highly competitive as compared to chitosan. Besides, BSF led to 40% of Mn removal from highly contaminated river water samples. For both biomaterials, bioflocculation was driven by charge neutralization and sweep flocculation mechanisms. For a given agricultural wastewater sample, both bioflocculants performed better than the commercial poly(aluminum chloride) for pH regulation and Fe removal.

Function integrated chitosan-based beads with throughout sorption sites and inherent diffusion network for efficient phosphate removal

A novel, cost-effective and biomass-derived adsorbent was fabricated by coating polydopamine on lanthanum-chitosan hydrogel (La-CS@PDA), which were endowed with a plentiful of amine groups. The diffusion structure of channel-network of La-CS@PDA made it well used in phosphate removal in wastewater treatment. The Langmuir isotherm delivered the maximal adsorption capacity about 195.3 mg/g, which was superior to most reported phosphate removal materials. More significantly, in the presence of competitive anions Cl^-, SO₄^2-, HCO₃^-, NO₃^-, F^- and HCrO₄^-, the resultant La-CS@PDA still conducted distinct selectivity for phosphate, which could be attributed to the selective binding sites of La species in the composite. Under continuous adsorption, the dynamic experimental data fitted well with Thomas model which imitates industrial practical application. By virtue of more fortes of high efficiency, ease of separation and expectable mechanical strength, as-prepared La-CS@PDA might be a promising candidate of dephosphorizing sorbent.