Chitosan Flocculation Research Articles

Preparation of the modified chitosan flocculant introduced acryloyloxyethyl trimethyl ammonium chloride and 2-acrylamido-2-methyl propane sulfonic acid for the treatment of papermaking wastewater

To solve the shortcomings of poor solubility, low cationic strength, and small molecular weight of chitosan (CTS), acryloyloxyethyl trimethyl ammonium chloride (DAC) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were introduced into the amino group of chitosan by graft copolymerization, and the modified chitosan flocculant CTS-DAC-AMPS was successfully prepared. The performance of CTS-DAC-AMPS in the treatment of papermaking wastewater was investigated, and the mechanism of the flocculation process was analyzed. The results showed that the crystal habit of CTS-DAC-AMPS was reduced, and the solubility range was broadened compared with CTS due to the introduction of DAC and AMPS. In addition, CTS-DAC-AMPS with quaternary ammonium and sulfonic groups prompted its cationic strength stronger than CTS. In addition to high thermal stability, CTS-DAC-AMPS, composed of two CTS molecules, one DAC molecule, and one AMPS molecule, had a long molecular chain. The results of flocculation experiments showed that the performance of CTS-DAC-AMPS in treating papermaking wastewater was better than that of unmodified CTS and commercially available flocculants. Based on the experimental results, the mechanism of CTS-DAC-AMPS treatment of papermaking wastewater was mainly charge neutralization.

Microalgae Biomass Harvesting Using Chitosan Flocculant: Optimization of Operating Parameters by Response Surface Methodology

Bioflocculants can be used for cost-effective harvesting of microalgae biomass on an industrial scale. This study investigates the flocculation-based harvesting approach to recovering Chlorella vulgaris microalgae biomass using chitosan biopolymer. Response surface methodology (RSM) was used to design the experiments and optimize the critical operating parameters. Box-Behnken Design (BBD) was employed at three levels, and 17 experimental runs were conducted to determine the optimal conditions and the relationship between operating parameters. The highest biomass recovery of 99.10% was achieved at the following optimized conditions: pH of 5, flocculation time of 45 min, and chitosan concentration of 10 mg/L. Both experimental results and model outputs indicated that pH significantly impacts microalgae harvesting and that process performance is less dependent on chitosan concentration and flocculation time. The quadratic model has shown the best fit with the experimental results. The results could be applied to large-scale microalgae harvesting applications to promote microalgae biomass recovery and reduce operating costs.

Dielectric barrier discharge plasma-modified chitosan flocculant and its flocculation performance

The flocculation performance of chitosan can be enhanced by grafting modification to overcome its disadvantages of poor water solubility. In this study, chitosan was modified by dielectric barrier discharge plasma and polymerized with acrylamide and aluminum chloride to synthesize a new chitosan-based flocculant, namely, chitosan–acrylamide–aluminum chloride (CA-PAC). After optimizing the synthesis conditions of CA-PAC, the best conditions were as follows: discharge time of 3 min, discharge power of 50 W, polymerization temperature of 60 °C, polymerization time of 3 h, total monomer concentration of 100 g/L, and m(AlCl3):m(CA) ratio of 2:1. Characterization was performed through SEM, XPS, FTIR, XRD, TG and 1H NMR. Results showed that the preparation of CA-PAC was successful. The influences of flocculant dosage, pH, and stirring intensity on flocculation efficiency were investigated. The removal efficiency of turbidity was 94.1 %. The investigation of the flocculation mechanism revealed that CA-PAC mainly relied on charge neutralization or the synergic action of electric neutralization, bridging, and roll–sweep under acidic and neutral conditions, but it depended on the joint action of adsorption bridging and net sweeping under alkaline conditions. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

Preparation and flocculation effect of copper ion imprinted chitosan flocculant

AbstractA copper ion imprinted chitosan flocculant (Cu2+@CTS) was synthesized by the molecular imprinting technique to improve the flocculation selectivity of chitosan to heavy metal ions. The effects of the amount of crosslinking agent, crosslinking time, temperature on the properties of the material were systematically investigated. Under the optimum preparation conditions, the flocculation rate and removal rate of Cu2+@CTS were 98.26% and 88.4%, respectively, 2.85 and 3.86 times higher than that of the unprinted chitosan flocculant. On this basis, the flocculation selectivity of Cu2+@CTS to Cu2+ in the presence of Zn2+, Ni2+ and other competitive ions was further explored. The experimental results indicated the removal rate of Cu2+ by Cu2+@CTS was as high as 70%–85%, which was 2.2–2.7 times that of other ions, while the removal rate of three metal ions by non‐imprinted chitosan flocculants was less than 35%. This study provided a reference for improving the selectivity of chitosan‐based flocculant to Cu2+.

Protein-folding-inspired approach for UF fouling mitigation using elevated membrane cleaning temperature and residual hydrophobic-modified flocculant after flocculation-sedimentation pre-treatment

Hydrophobic-modified flocculants have demonstrated considerable promise in the removal of emerging contaminants by flocculation. However, there is a lack of information about the impacts of dosing such flocculants on the performance of subsequent treatment unit(s) in the overall water treatment process. In this work, inspired by the ubiquitous protein folding phenomenon, an innovative approach using an elevated membrane cleaning temperature as the means to induce residual hydrophobic-modified chitosan flocculant (TRC), after flocculation-sedimentation, to reduce membrane fouling in a subsequent ultrafiltration was proposed; this was evaluated in a continuous flocculation-sedimentation-ultrafiltration (FSUF) process treating samples of the Yangtze River. The hydrophobic chains of TRC had similar temperature-dependent hydrophobicity to those of natural proteins. In the 40-day operation of the FSUF system with combined dosing of alum and TRC, a moderately elevated cleaning water temperature (45 °C) of both backwash with air-bubbling and soaking with sponge-scrubbing cleaning, significantly reduced reversible and irreversible fouling resistance by 49.8%∼61.3% and 73.9%∼83.3%, respectively, compared to the system using cleaning water at 25 °C. Material flow analysis, statistical analysis, instrumental characterizations, and computational simulations, showed that the enhanced fouling mitigation originated from three factors: the reduced contaminant accumulation onto membranes, the strengthened membrane-surface-modification role of TRC, and the weakened structure of the fouling material containing TRC, at the elevated cleaning temperature. Other measures of the performance, these being water purification, membrane stability and economic aspects, also confirmed the potential and feasibility of the proposed approach. This work has provided new insights into the role of hydrophobic-modified flocculants in membrane fouling control, in addition to emerging contaminant removal, in a FSUF surface water treatment process.

The Use of Chitosan for Flocculation Recovery of Bacillus Biomass Grown on Dairy and Wine Industry Effluents

The downstream processing of efficient biomass-based microbial biopesticides is heavily reliant on obtaining the largest concentration of viable cells in the most cost-effective manner. The goal of this research was to assess the ability of chitosan flocculation to recover bacterial Bacillus sp. BioSol021 biomass from the broth after biological treatment of wastewaters from the dairy and wine industries. Second-order factorial design models were used to estimate the effect of chitosan concentration and mixing speed on flocculation efficiency, settling velocity, and antimicrobial activity against Aspergillus flavus, i.e., inhibition zone diameter. Response surface methodology was followed by multi-objective optimization by applying the desirability function (DF) and genetic algorithm (GA). The optimum values for flocculation efficiency, settling velocity, and inhibition zone diameter for cheese whey effluent were 88%, 0.10 mm/s, and 51.00 mm, respectively. In the case of winery flotation effluent, the optimum values were flocculation efficiency 95% and settling velocity 0.05 mm/s, while the inhibition zone diameter was 48.00 mm. These results indicate that utilizing chitosan as a flocculation agent not only fits the criteria for effective downstream processing, but also has a synergistic effect on Bacillus sp. antibacterial activity.

A novel cationic-modified chitosan flocculant efficiently treats alkali‒surfactant‒polymer flooding-produced water

A novel cationic-modified chitosan flocculant efficiently treats alkali‒surfactant‒polymer flooding-produced water

Mussel-Inspired Catechol-Grafted Quaternized Chitosan Flocculant for Efficiently Treating Suspended Particles and Refractory Soluble Organic Pollutants

It remains challenging yet of great importance to develop a qualified biopolymer-derived flocculant in treating complex high-salinity wastewaters polluted by suspended solids and refractory soluble organic substances such as organic dyes. The key to this success is to endow the developed flocculants with versatile intermolecular and interfacial interactions in high salinity to trigger effective flocculation. Herein, inspired by mussel’s powerful wet adhesion in a salted marine environment to diverse interfaces, we develop a mussel-inspired chitosan-based flocculant (CQ-CS) by simultaneously grafting catechol and cationic trimethylammonium groups to chitosan backbones. Compared with its cationic compartment, the optimal dosage of CQ-CS is decreased greatly after introducing catechol groups. Moreover, CQ-CS works in a wide pH range from 2 to 7 and can achieve more than 95% removal efficiency of soluble organic dyes and suspended particles such as anionic dyes and kaolin clay at the optimal dosages. More importantly, the flocculation performance of CQ-CS exhibits excellent tolerance to the salinity. As NaCl concentration increases from 0 to 2000 mg/L, CQ-CS maintained similar removal efficiencies for organic dyes, while the removal efficiency of quaternized chitosan (Q-CS) for organic dyes decreased by approximately 8% at this salinity. Finally, CQ-CS exhibits excellent flocculation performance to industrial dyeing wastewaters.

A novel approach for microalgal cell disruption and bioproducts extraction using non-thermal atmospheric plasma (NTAP) technology and chitosan flocculation

Microalgal cell disruption and bio-product extraction still remain as major challenging steps for biomass downstream processing. In this study, a sustainable approach of using non-thermal atmospheric plasma (NTAP) and chitosan flocculation was developed for microalgal cell disruption and bio-product recovery from wet C. Sorokiniana. For this purpose, the performance of NTAP treatment for cell disruption and extraction of protein, carbohydrate and lipid was investigated by using different applied voltages (8–16 kV). Then, the application of chitosan on recovery of bioproducts from the culture medium was evaluated. Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) images were used to analyze the flocculation mechanism and for flocs characterization. Additionally, the energy consumption and efficiency of the NTAP process were analyzed. According to the NTAP results, the highest cell disruption of 75% was achieved under the applied voltage of 16 kV. However, in the case of bioproducts extraction, the optimal applied voltage was 12 kV which was able to yield 41, 24 and 36 (%CDW) of protein, carbohydrate and lipid, respectively. Adding 100 mg/L chitosan efficiently recovered the released protein (65%) and carbohydrate (85%) from culture medium, while the highest lipid recovery (60%) was achieved at 150 mg/L chitosan addition. This study proved that the utilization of NTAP and chitosan treatment can be considered as a promising approach for valuable products extraction from microalgae.

A rapid, efficient and eco-friendly approach for simultaneous biomass harvesting and bioproducts extraction from microalgae: Dual flocculation between cationic surfactants and bio-polymer

Microalgal biomass harvesting and cell disruption are the main bottlenecks for downstream processing of microalgae such as high-value bioproducts extraction and biofuels production. In this study, we evaluated the performance of dual flocculation between cationic surfactants and bio-polymer of chitosan for simultaneous biomass harvesting and bioproducts extraction from Chlorella sorokiniana microalgae. First, the effects of individual natural flocculants of chitosan and two cationic surfactants: cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on biomass harvesting were studied. Next, the synergistic effect of dual flocculation between the cationic surfactants and chitosan on harvesting efficiency, time and flocculant dosage was investigated. Finally, we evaluated the potential of high value bioproducts extraction from microalgae after the individual and dual flocculation processes. Zeta potential analysis and microscopic images were employed to achieve mechanistic understanding. Maximum biomass harvesting efficiencies of 85 %, 88 % and 78 % were achieved using individual flocculants of chitosan, CTAB and DTAB, under their optimum dosages of 100, 400 and 4000 mg/L, respectively. A significant synergistic effect of dual flocculation between chitosan (C) and cationic surfactants on biomass harvesting efficiency (CTAB-C: 99 % and DTAB-C: 97 %), settling time (CTAB-C: 2 min and DTAB-C: 5 min) and optimum dosage of surfactants (CTAB-C: 100 mg/L and DTAB-C: 1000 mg/L) was observed. The synergistic effect was associated with multiple flocculation mechanisms of charge neutralization and bridging induced by cationic surfactants and chitosan, respectively. Furthermore, bioproducts recovery efficiencies of 12 %, 25 % and 15 % of cell dry weight were achieved for protein, carbohydrate and lipid, respectively by using dual flocculation of CTAB surfactant and chitosan at much lower dosage of 100 mg/L.

Amine-Modified Chitosan Flocculant Synthesized via Single-Mode Microwave Method for Laundry Wastewater Treatment.

In this study, an effective and environmentally friendly polyaminated cross-linked chitosan (M-PACTS) flocculant was successfully synthesized via circular focus single-mode microwave synthesizer irradiation. Epichlorohydrin and tetraethylenepentamine were used as the cross-linking agent and active cationic reagent, respectively. The same formation was used to prepare cationic lightly cross-linked chitosan (C-PACTS) via the conventional heating method. The flocculant was characterized using Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The flocculation capability of C-PACTS and M-PACTS was compared using laundry wastewater as a model pollutant. The pH, PACTS dosage, temperature, stirring rate, stirring time, and setting time were systematically investigated. The experimental results showed that circular focus single-mode microwave synthesizer irradiation was a more efficient method to modify chitosan. M-PACTS exhibited a higher capacity for turbidity and chemical oxygen demand (CODCr) removal. Under optimal conditions, the removal rate values of M-PACTS were up to 96% (turbidity) and 78% (CODCr). The proposed PACTS is suitable for treatment of polluted wastewater in an eco-friendly manner without causing secondary pollution.

The study of flocculation efficiency of microalgae Chlorella vulgaris (Chlorophyta) using chitosan

Recently, many studies on Chlorella vulgaris have been carried out because C vulgaris contains many nutrients that are very useful for humans and the culture of marine organisms as natural foods. Until now, the biggest production cost is the harvesting process cost., This research aims to study the flocculation efficiency of the microalgae C vulgaris using chitosan flocculants. In this study, the treatments were chitosan concentration (10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 ppm) and settling time (10, 20, 30 and 40 minutes). Each treatment was replicated three times. Based on the result of the study, the use of chitosan concentration of 20 ppm showed that the flocculation efficiency value was greater than 90% at the deposition (settling) times of 20, 30, and 40 minutes. Even though the higher the chitosan concentration value given, the greater the flocculation efficiency value, the statistical test showed no significant differences between flocculation efficiency in different concentrations of chitosan and time settling (P> 0.05).

Preparation and performance of CTS-AM-ETA as a modified chitosan flocculant

Preparation and performance of CTS-AM-ETA as a modified chitosan flocculant

Superior environmental stability of gelatin/CMC complex coacervated microcapsules via chitosan electrostatic modification

As an electrostatic deposited coating for gelatin/sodium carboxymethyl cellulose (CMC) coacervates, chitosan was applied to improve their stability and resistance against harsh environment (extreme pH, high ionic strength and high temperature). With eugenol as the core material, gelatin/CMC microcapsules (SM) and gelatin/CMC microcapsules coated by chitosan (DM) were prepared, and their structures were further characterized. To minimize the bridging flocculation of chitosan by the electrostatic interaction, SM were prepared at pH 4.4 and coated by chitosan at pH 5.0. According to the thermal gravimetric analysis results, the degradation temperature of DM was 292 °C compared to 265 °C of SM. The eugenol retention of SM decreased from 65% to 20% as pH increased from 2 to 10, while DM always kept it over 70% between pH 2–10. Moreover, the eugenol retention of DM remained at 70%–80% with an ionic strength of 0–200 mmol/L (pH 4 and 10). CLSM and SEM confirmed that the SM were coated with chitosan, and the Fourier transform infrared (FTIR) spectra showed that electrostatic force played a main role in the binding of gelatin, CMC and chitosan. Circular dichroism (CD) revealed that the secondary structure of gelatin molecules was changed from a flexible pattern to an ordered pattern due to the addition of CMC and chitosan. Consequently, the chitosan coating could improve the stability of complex coacervated microcapsules in harsh environments, which might have a broad prospect to protect essential oils and flavor substances against severe harsh environmental stresses during in the processing of food and pharmaceuticals.

Chitosan flocculation associated with biofilms of C. saccharolyticus and C. owensensis enhances biomass retention in a CSTR

Cell immobilization and co-culture techniques have gained attention due to its potential to obtain high volumetric hydrogen productivities (QH2). Chitosan retained biomass in the fermentation of co-cultures of Caldicellulosiruptor saccharolyticus and C. owensensis efficiently, up to a maximum dilution rate (D) of 0.9 h−1. Without chitosan, wash out of the co-culture occurred earlier, accompanied with approximately 50% drop in QH2 (D > 0.4 h−1). However, butyl rubber did not show as much potential as carrier material; it did neither improve QH2 nor biomass retention in continuous culture. The population dynamics revealed that C. owensensis was the dominant species (95%) in the presence of chitosan, whereas C. saccharolyticus was the predominant (99%) during cultivation without chitosan. In contrast, the co-culture with rubber as carrier maintained the relative population ratios around 1:1. This study highlighted chitosan as an effective potential carrier for immobilization, thereby paving the way for cost – effective hydrogen production.

Enhanced chitosan flocculation for microalgae harvesting using electrolysis

Harvesting microalgae from water and wastewater streams is important for both environmental remediation and re-cycling of both algal material and associated nutrients. Chitosan is widely used as an environmentally friendly flocculant in this process. Charge neutralization is a key operating mechanism for chitosan flocculation in microalgae harvesting. Alkaline conditions have been conventionally used to modify chitosan to create an increase in charge neutralization. However, it is often difficult to operate the chemical processes needed for this method, which also pose environmental risks. In this study, a simple and environmentally safe method to increase chitosan charge neutralization using electrolysis was proposed and tested in the harvest of microalgae. The results demonstrate that the electrolysis produced a charging effect on the chitosan and exhibited a significant positive relationship with current intensity (r2 = 0.91, P < 0.05). When the electrolysis was operated at 0.2, 0.4, and 0.6 A, the charge neutralization of chitosan increased by 2.05, 4.99, and 10.86 mV/mg, respectively. As the charge neutralization increased, chitosan flocculation yielded a higher microalgae harvesting efficiency at a lower chitosan dosage. One of the possible mechanisms for the increased charge neutralization ability is the deacetylation of the acetyl groups caused by electrolysis. This idea needs further study that includes identifying a chitosan structure change. This study proposed a novel strategy for modifying chitosan and its derivatives for enhancing flocculation in microalgae-based engineering.

Heavy metal removal from aqueous solutions by chitosan-based magnetic composite flocculants

In this study, three magnetic flocculants with different chelating groups, namely, carboxymethyl chitosan-modified Fe3O4 flocculant (MC), acrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCM), and 2-acrylamide-2-methylpropanesulfonic acid copolyacrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCAA) were prepared, synthesized, and characterized by photopolymerization technology. They were applied to the flocculation removal of Cr(III), Co(II), and Pb(II). The effect of flocculation condition on the removal performance of Cr(III), Co(II), and Pb(II) was studied. Characterization results show that the three magnetic carboxymethyl chitosan-based flocculants have been successfully prepared with good magnetic induction properties. Flocculation results show that the removal rates of MC, MCM, and MCAA on Cr(III) are 51.79%, 82.33%, and 91.42%, respectively, under the conditions of 80 mg/L flocculant, pH value of 6, reaction time of 1.5 hr, G value of 200 s−1, and precipitation magnetic field strength of 120 mT. The removal rates of Co(II) by MC, MCM, and MCAA are 54.33%, 84.99%, and 90.49%, respectively. The removal rates of Pb(II) by MC, MCM, and MCAA are 61.54%, 91.32%, and 95.74%, respectively. MCAA shows good flocculation performance in composite heavy metal-simulated wastewater. The magnetic carboxymethyl chitosan-based flocculant shows excellent flocculation performance in removing soluble heavy metals. This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove heavy metals in wastewater.

Flocculation properties of eight microalgae induced by aluminum chloride, chitosan, amphoteric polyacrylamide, and alkaline: Life-cycle assessment for screening species and harvesting methods

The flocculation performances of AlCl3, chitosan, amphoteric polyacrylamide (acrylamide-methacrylic acid ester-acrylic acid copolymer [ACPAM]), and NaOH for eight microalga species were investigated. AlCl3 had wide application for both freshwater and marine microalgae while NaOH could only flocculate marine microalgae. By contrast, chitosan was very effective to freshwater species with low dosage demand; ACPAM was only valid for three freshwater species. The settling times, concentration factors (CF), and capillary suction times (CST) were measured. The settling times with ACPAM (0.5–0.6 min) were the shortest while flocculation by NaOH had the longest settling times (13–40 min). The CF determined the volume of microalgae slurry, which in turn affected dewatering. The CST was used to evaluate polyacrylamide (PAM) demand in dewatering (filter press) using a model developed in this study. Life-cycle assessment identified the optimal harvesting methods for the eight species using data from this study and the literature. The analyses revealed that chitosan flocculation + filter press was the best approach for five species and AlCl3 flocculation + filter press or two-step centrifugation was optimal for the remaining three species. Coccomyxa sp. K.J., Chlorella vulgaris, and Tetradesmus obliquus were screened for biodiesel production in consideration of the environmental impact and their lipid contents.

Flocculation of emulsified oily wastewater by using functional grafting modified chitosan: The effect of cationic and hydrophobic structure

In this work, modified chitosan flocculants (MCS) was synthesized by using chitosan (CS), acrylamide, cationic monomers and hydrophobic monomers via low-pressure UV-initiated copolymerization. The flocculation performance of MCS was evaluated in emulsified oily wastewater treatment. The effect of cationic and hydrophobic structure on oil removal was studied, and the interactions between these functional groups and the components in oil were also analyzed. Results suggested that MCS flocculants exhibited excellent oil removal efficiency in a wide pH range (2.0‒10). The flocculation efficiency of 91 % was achieved at the dosages of 0.6 mL/L (6 mg/L). During pH of 2.0-10, the optimal cationic and hydrophobic monomer was DMC and VT, respectively. Silane groups were favorable for oil removal than the other hydrophobic structures. The cationic groups expanded the optimal pH range of MCS in flocculation, whereas hydrophobic groups considerably reduced the dosage of MCS. The experimental results showed that alkane, cyclic aromatic hydrocarbon compounds in oil can be easily removed by using MC4, whereas cycloalkanes compounds was effectively removed by MC6 and MC7 because of preferable demulsification capacity, and the hydrophobic interaction, interfacial adsorption and electrostatic attraction played the dominant in flocculation. Thus, the synthesized MCS is favorable for emulsified oily wastewater treatment.

Evaluating the potential of carbohydrate-rich microalga Rhodosorus sp. SCSIO-45730 as a feedstock for biofuel and β-glucans using strategies of phosphate optimization and low-cost harvest

With the increase of global energy consumption, bioenergy from microalgae has been recognized as a potential alternative choice. A novel carbohydrate-rich microalgal strain, isolated from Xisha Islands (China), was identified as Rhodosorus sp. SCSIO-45730. To accumulate biomass for bioenergy production, strategies of phosphate optimization and chitosan flocculation were used to evaluate its potential for the production of biomass, total carbohydrates, and β-glucans. The biomass of this alga reached 12.3 ± 0.1 g L−1 in vertical bubble column photobioreactors at the phosphate concentration of 120 mg L−1, and the productivities of total carbohydrates and β-glucans maximized up to 242.6 ± 2.3 mg L−1 day−1 and 108.1 ± 4.0 mg L−1 day−1, respectively. Simultaneously, flocculation results demonstrated that the recovery rate of the biomass, total carbohydrates, and β-glucans were over 90% at a low chitosan concentration of 3 mg L−1. The flocs were easily collected and washed through a 300-mesh bolting cloth, presenting an ultralow harvest cost of 2.93 US$ per tonne of biomass. In summary, addition of suitable phosphate and flocculation with low chitosan concentration could be effective strategies to enhance the commercial potential of Rhodosorus sp. SCSIO–45730 as a feedstock for biofuel and β-glucans.