Biodegradable Flocculants Research Articles

An eco-friendly approach to separate emulsified oil from water using all natural materials of chitosan and beach sand

Oil-contaminated water from oil and gas exploration remains the industry’s primary waste stream. The common method of using chemical coagulation/flocculation followed by air flotation has drawbacks such as generating non-biodegradable and toxic sludge and high operational costs. This study presents an eco-friendly alternative utilizing chitosan and beach sand to remove emulsified oil from water. Chitosan acts as a biodegradable flocculant, while beach sand aids in high-density floc formation and accelerates settling velocity. This approach achieved up to 94 % oil removal efficiency and reduced settling time from 90 to 15 min by using 100 mg/L chitosan and 500 mg/L beach sand with a particle size distribution of 50–100 μm. Shorter settling time reduces capital expenditure compared to conventional methods. Additionally, using natural materials like chitosan and beach sand minimizes toxic sludge generation. This eco-friendly approach offers a promising alternative to conventional methods for treating oily wastewater.

Deciphering the Dual Roles of an Alginate-Based Biodegradable Flocculant in Anaerobic Fermentation of Waste Activated Sludge: Dewaterability and Degradability.

Biodegradable flocculants are rarely used in waste activated sludge (WAS) fermentation. This study introduces an alginate-based biodegradable flocculant (ABF) to enhance both the dewatering and degradation of WAS during its fermentation. Alginate was identified in structural extracellular polymeric substances (St-EPS) of WAS, with alginate-producing bacteria comprising ∼4.2% of the total bacterial population in WAS. Owing to its larger floc size, higher contact angle, and lower free energy resulting from the Lewis acid-base interaction, the addition of the prepared ABF with a network structure significantly improved the dewaterability of WAS and reduced capillary suction time (CST) by 72%. The utilization of ABF by an enriched alginate-degrading consortium (ADC) resulted in a 35.5% increase in the WAS methane yield owing to its higher hydrolytic activity on both ABF and St-EPS. Additionally, after a 30 day fermentation, CST decreased by 62% owing to the enhanced degradation of St-EPS (74.4%) and lower viscosity in the WAS + ABF + ADC group. The genus Bacteroides, comprising 12% of ADC, used alginate lyase (EC 4.2.2.3) and pectate lyase (EC 4.2.2.2 and EC 4.2.2.9) to degrade alginate and polygalacturonate in St-EPS, respectively. Therefore, this study introduces a new flocculant and elucidates its dual roles in enhancing both the dewaterability and degradability of WAS. These advancements improve WAS fermentation, resulting in higher methane production and lower CSTs.

Alginates as Green Flocculants for Metal Oxide Nanoparticles

AbstractFlocculation is used for the removal or separation of colloids, e.g. in water treatment and mineral processing. Alginates are linear, anionic biopolymers composed of mannuronic (M) and guluronic (G) acids. The relative amount and distribution of M and G impact the ion-binding and gel-forming properties of the polymer, but still no one has yet addressed the impact of alginate composition on flocculation of nanoparticles or mineral particles. Our results showed that the distribution of G was important for flocculation, especially when Ca2+ was used as activating ion. With Ce3+ as activating ion, the shape and size of flocs were affected by alginate acetylation. This work expands the knowledge about the flocculation behavior of alginates and demonstrates that both bacteria- and algae-derived alginates can be potential biodegradable flocculants of ultrafine particles for mineral processing industry.

Cause analysis for fouling mitigation, techno-economic and toxicity reduction assessments of hairwork dyeing effluent reclamation via membrane-based hybrid systems

Based on the continuous innovation of membrane materials and partnered reagents, it is necessary to timely evaluate the efficiency improvement of a package of relevant wastewater treatment processes and clarify the associated pivotal causes. For this purpose, the root-cause analysis for fouling mitigation derived from influent characteristics, the techno-economic and toxicity reduction assessments of hairwork dyeing effluent (HDE) reclamation via three membrane-based hybrid systems approaching zero discharge were systematically carried out. The experimental results showed that with the aid of a novel efficient and biodegradable flocculant, the lower fluorescence peak intensity, the more negative zeta potential and the quantitatively dominant hydrophobic components in feedwater all helped to mitigate the same-charged hydrophilic TFN-CQDs membrane fouling due to modification of itself. Accordingly, the optimal processing technology required the minimum amount and replacement frequency for membrane elements and less than 1/5 and 1/10 of the energy consumption and chemicals of their counterparts, respectively. Besides, it also decreased the waste (brine) stream volume fraction to 7%, and greatly increased B/C value of supernatant to 0.667, thus strengthening “intermediate control” of pollutants. Although the organic contaminant components in HDE basically transcend the aromatic/hydrophilic differences in producing biotoxicity, all schemes still had good performance in its elimination. Undoubtedly, the outcome of these evaluations will provide valuable technical guidance for scaling-up the prototype results and promoting the cleaner production of local wig enterprises.

Evaluating dissolved air flotation for oil/water separation using a hybridized coagulant of ferric chloride and chitosan

Dissolved air flotation (DAF) is a separation technology widely used in the industry to reduce oil concentrations in wastewater. However, there are some issues with the existing DAF system, including high chemical cost, environmental pollution by chemical residual in the effluent, and generation of non-biodegradable sludge. In this study, an environmentally friendly and cost-effective DAF process was proposed and tested for separating emulsified oil from water. A hybrid coagulant/flocculant system with ferric chloride as a coagulant and chitosan as a bio-degradable flocculant was used to enhance the efficiency of oil/water separation. The findings of this study showed that the hybrid configuration led to (i) 37% reduction in chemical costs (ii) 90% reduction in the use of non-biodegradable ferric chloride and (iii) 50% reduction in flocculator footprint when compared to individual coagulants. This proposed dosing strategy also has a broader operating pH range between 5 and 9 and wider applicability for both fresh and high salinity water. The results from this study contribute to the wider, environment-friendly, and cost-effective application of air flotation for oil/water separation.

The potency of microbial flocculant produced by B. licheniformis using molasses as the carbon source and its application in food industry wastewater treatment

Flocculants play an important role in removing colloids, suspended particles, and dyes from industrial wastewater. Presently, synthetic flocculants have been widely applied in the industrial sector as colloidal aggregates. The use of these flocculants is known to harm human health and the environment for them being neurotoxic, strong carcinogens, and cannot be degraded by microbes. Therefore, bio-flocculants are an alternative to reduce the usage of synthetic flocculants. Moreover, studies on the application of food industry wastewater as food ingredients are increasingly being developed. It is estimated that the need for safe and biodegradable flocculants will also increase. This study was conducted to examine the production of bio-flocculants from Bacillus licheniformis using molasses as a carbon source under different molasses concentrations (15 g/l and 30 g/l) and incubation times (24, 48 and 72 h). The bio-flocculant from B. licheniformis was then applied to treat tofu industry wastewater for turbidity removal, reduction of Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The highest flocculation rate of bio-flocculant was achieved at 46,62% to kaolin suspension by 15 g/l molasses within 24 h culture time. On the purification of tofu industry wastewater, the efficiency of turbidity removal of 15 g/l and 30 g/l molasses concentration variations were 70.03% and 43.04% respectively. Bio-flocculant produced also performed great BOD and COD removal by 75.9% and 80.2% which proceed by variation of 15 g/l molasses within 24 h incubation time. These high rate of turbidity, COD, and BOD removal by bio-flocculant indicates its effectiveness on industrial application in wastewater treatment.

Biowaste-based biodegradable flocculants for clean and sustainable tailings management in industrial mining and mineral processing

Massive fluid tailings discharged from industrial mining and mineral processing operations pose numerous economic and environmental challenges. To remove water and condense tailings into sediment, we developed a novel bioflocculant from specified risk materials, a particular type of waste biomass from the animal rendering industry. By properly controlling key synthesis conditions, the bioflocculant successfully met industrial requirements for fluid tailings treatment, including enhanced short-term tailings settling and improved ultimate water removal extent. Settling tests using real industrial fluid tailings showed that the synthesized bioflocculant enabled an initial settling rate 4 magnitudes higher than the control case and achieved 93.2% the dewatering efficiency of a commercial flocculant (hydrolyzed polyacrylamide; HPAM). In contrast to HPAM, our bioflocculant can achieve tailings settling without gypsum, a common processing aid that can hinder downstream industrial operations. More importantly, growth tests using two common microorganisms (Saccharomyces cerevisiae and Escherichia coli) suggested that the bioflocculant can be easily degraded, indicating reduced negative environmental impacts after its use. Taken together, this study demonstrates the great potential of implementing a biodegradable bioflocculant from proteinaceous wastes for clean and sustainable management of mining and mineral processing fluid tailings.

Synthesis of Polymer Grafted Starches and Their Flocculation Properties in Clay Suspension

Starch-based flocculants have been emerged as a promising alternative to conventional synthetic flocculants in wastewater treatment, especially for the treatment of oil sand tailings, as they are low cost, safe, biodegradable, fairly shear-stable, readily available from reproducible agricultural resources, and do not result in secondary pollution. In this paper, three types of polymer-grafted starches (St-g-Polymer) with different charge properties were synthesized and their molecular structures were controlled by atom transfer radical polymerization (ATRP). The correlations between the charge properties of starch-based flocculants, external environmental parameters, and flocculation performance were systematically investigated by conducting jar tests under various environmental conditions. It was found that the charge properties of the branch chain had a significant impact on flocculation performance. The cationic St-g-Polymer demonstrated the best performance due to the grafting of the cationic monomer to the starch backbone which improved the solubility of the copolymer and aided in the removal of small/water-soluble particles. The results obtained could assist in guiding the selection and design of suitable biodegradable flocculants when treating targeted wastewater.

Synthesis and Dewatering Properties of Cellulose Derivative-Grafting DMC Amphoteric Biodegradable Flocculants

Flocculant played an important role in water treatment and sludge dewatering. It is imperative to design and synthesize an eco-friendly and biodegradable flocculant based on natural polymer. In the present work, a new amphoteric CMC-based flocculant, CMC-g-PDMC was synthesized via grafting DMC onto hydroxyl of CMC initiated by potassium persulfate under traditional heating condition. The optimal graft copolymerization condition was optimized by orthogonal experiment. The structure, morphology and thermostability of the obtained graft copolymer were characterized by measuring FT-IR, XRD, SEM and TGA analyzer, respectively. Moreover, comparing with the commercial flocculant PAM, PAC and CPAM, the dewatering capacity of municipal sludge was evaluated using CMC-g-PDMC by FCMC, SRF, SVI and light transmittance. It suggested that the flocculation to municipal sludge was related to the ion properties of the flocculant.

Physico-Chemical Treatment of a Wastewater Collector Loaded with Metals and Suspension Material by The Solution of Raw Carica papaya Latex

The papaya (Carica papaya), of the family Caricaceae, is a tree-like tropical plant, native to Central and South America. Papaya cultivation extends to all warm and humid countries. The present study consists in using the solution of raw Carica papaya latex (SLCP) cultivated in Benin as a natural biodegradable flocculant in a physico-chemical process to treat liquid discharges loaded with metals including iron, copper, zinc, and manganese; and suspended matter, and also to test its efficiency against other products commonly used in wastewater treatment. The tests were carried out on water samples from the wastewater collector that runs through the Agla district in Cotonou.
 The comparative study with a commonly used flocculant, aluminium sulphate, showed outstanding competitiveness with a high flocculation power for the solution of Carica papaya raw latex. In six water samples from the collector with average concentrations of iron, copper, zinc and manganese of 18.20 mg/L ; 2.50mg/L ; 3.80 mg/L and 3.70 mg/L respectively, the percentages of metal removal exceeded 90% for iron and manganese and around 85% for copper and zinc with the combination FeCl3 + SLCP. The NaOH + SLCP combination showed a very significant effect on the removal of metals (96% reduction) and suspended matter.

Use of ultrasound for aiding lipid extraction and biodiesel production of microalgae harvested by chitosan

ABSTRACT In this work, chitosan, a biodegradable flocculant, was investigated to determine its utility in flocculating microalgae, its effect on cell integrity, and its impact on lipid extraction and the conversion to fatty acid methyl ester (FAME). Results showed that chitosan adequately performed flocculation on Chlorella vulgaris microalgae and achieved a high harvesting efficiency of 96.35 ± 1.96% when implemented under the following conditions: chitosan dose = 120 mg/L−1, pH = 5, mixing speed = 150 rpm for 20 min, followed by 10 min of settling time. Moreover, scanning electron microscope (SEM) combined with transmission electron microscope (TEM) demonstrated that chitosan protected the cells’ structure from morphological damage. Finally, the highest lipid extraction yield and biodiesel production was obtained from the chitosan-harvested biomass when the microalgae were pretreated with ultrasound.

Preparation and flocculation properties of biodegradable konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride)

Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic comonomer to develop biodegradable flocculants. The structure of KGM-g-PTMAAC was characterized by FTIR, 13C solid-state NMR, elemental analysis (EA) and SEM. Thermal properties of KGM-g-PTMAAC were studied by thermal gravimetric (TG) analysis. In addition, flocculation properties of KGM-g-PTMAAC were investigated in a kaolin suspension. The results of the FTIR, NMR, and EA showed that the cationic moiety containing quaternary ammonium has been introduced in the backbone of KGM. SEM images indicated that the surface of KGM-g-PTMAAC was rougher than that of KGM. TG results indicated that the thermal stability of KGM-g-PTMAAC was different to that of KGM. The obtained products had a good biodegradable performance. Moreover, the results of the flocculation test showed that KGM-g-PTMAAC could be potentially used as a good flocculating agent.

Enhanced removal of suspended colloidal particles from turbid water using a modified microbial flocculant

Microbial flocculant (MBF), as an efficient, environmental friendly and biodegradable flocculant, has been widely studied in water treatment. The cationic modification of MBF would improve its charge neutralization and extend its application. In this study, the effect of mAM:mDMDAAC, mMBF:m(AM + DMDAAC), reaction temperature and initiator dosage on the molecular weight of modified MBF were investigated. The optimal synthesis condition was obtained. Modified MBF performed well in the removal of suspended colloidal particles from water. It possessed the potential application in the surface water treatment.

2,3,6-Tricarboxylate Cellulose as a Fully Biodegradable Flocculant: Efficient Synthesis and Flocculation Performance

Cellulose-based flocculants have shown excellent performance for wastewater flocculation, being low-cost and eco-friendly. However, they are still disturbed by the problems of incomplete biodegradability and unstable chemical structure. In the present study, 2,3,6-tricarboxylate cellulose (TCC) was developed as a novel fully biodegradable flocculant to deal with the preceding problems. The key carboxymethylation of cellulose was first carried out to make the subsequent NaIO4 oxidation occur under homogeneous conditions, which greatly enhanced the carboxylate content of the final TCC products. The chemical structure and solution properties of the TCCs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer system (XRD), field emission scanning electron microscopy (FESEM), charge density, particle size, and zeta potential. The flocculation performance of the TCCs was evaluated preliminarily by the turbidity removal of kaolin suspension. The positive results showed that all the TCC products had high carboxylate contents (more than 10 mmol/g) and zeta potentials. They exhibited excellent flocculation performance for the kaolin suspensions, in which the residual turbidities decreased from 610 to 14.9 NTU. Considering the degradation of cellulose caused by excessive NaIO4 oxidation, the TCC IV, together with its synthesis technology, could be used for practical applications in wastewater flocculation.

Production of a biodegradable flocculant from cotton and evaluation of its performance in coagulation-flocculation of kaolin clay suspension: Optimization through response surface methodology (RSM)

Flocculants are widely used along with coagulant to increase the efficiency of coagulation-flocculation process for removal of colloidal particles from wastewaters. The most widely used flocculants are synthetic which have some problems such as non-biodegradability and release of toxic residual monomers. The main aim of this study is to evaluate the performance of cellulose sulfate (CS), which was synthesized through sulfonation of cotton, as a biodegradable and natural-based flocculant. Reaction time as an important factor in the sulfonation reaction was optimized for obtaining CS with high charge density and suitable fiber size. The sulfate content, charge density (CD) and morphology of each CS were determined to investigate and select the best CS for the flocculation process. A suspension containing kaolin clay was used as a colloidal test solution and coagulation was performed using alum (as a coagulant) and CS (as a flocculant). Optimization was performed using response surface methodology (RSM). The optimization results showed that CS had a good performance in turbidity reduction in coagulation-flocculation treatment and maximum turbidity reduction (98.9%) was obtained at alum dosage of 23.1mg/L, CS dosage of 7.2mg/L and pH 6.2. The results showed that the pH variation had insignificant effect on the CS dosage. Zeta potential measurements and microscopic photos of flocs confirm charge neutralization and bridge formation in flocculation using cellulose sulfate, respectively. Also, the total chemical consumption reduced compared with the use of alum alone. As a consequence, CS can be considered as a suitable alternative for conventional flocculants.

Isolation and characterization of a bioflocculant from Bacillus megaterium for turbidity and arsenic removal

A biodegradable flocculant was produced during growth of Bacillus megaterium. The major component of the bioflocculant was found to be a polysaccharide composed of some proteins. Fourier transform infrared (FTIR) spectra analysis revealed the presence of carboxyl and hydroxyl groups in the bioflocculant, and thermal characterization by differential scanning calorimetly (DSC) showed the transition and crystalline melting point at 90-105 degrees C. The effects of bioflocculant dosage and pH on the flocculation of mineral suspensions were evaluated. The bioflocculant exhibited good flocculating capability on mineral suspensions and achieved flocculating efficiencies of 90 percent for k-aolinite and 85 percent for hematite suspensions at a dosage of only 5 mL/L. The maximum arsenite removal was found to be 90 percent at a bioflocculant dosage of 2 g/L, which is better than traditional chemicalflocculants. This study demonstrates that microbial bioflocculants have potential for application in environmental cleanup, such as in the flocculation of mineral fines and in the remediation of solutions that contain toxic heavy metals.

Combined Precipitation/Flocculation Method for Nutrient Recovery from Greenhouse Wastewater

Phosphorus (P) pollution from greenhouse wastewater is currently a major issue. A treatment method that can efficiently remove P concentrations ([P]) that fluctuate between greenhouse systems and throughout the year is required. An ideal method would also recover nutrients in a reuseable form. A combined precipitation/flocculation process incorporating addition of lime and a biodegradable flocculant (guar gum, cationic starch, or chitosan) was investigated for providing optimized P removal and recovery. Effectiveness of this process was evaluated in simulated wastewater of low and high alkalinity, as well as real greenhouse wastewater. Precipitation via lime addition reduced total P to below 1 mg·L−1 in low-alkalinity simulated wastewater, but high alkalinity slightly inhibited separation. This inhibition was overcome by flocculation via guar gum or cationic starch addition, which improved separation efficiency and reduced separation time, although chitosan was ineffective as a flocculant. The precipitation/flocculation method was found to be effective for treating real greenhouse wastewater, although effectiveness varied with variation in wastewater composition. Recovered precipitate contained 57.4 g·kg−1 P as well as high levels of Ca, Mg, K, Fe, and Zn. This study demonstrates a P separation process incorporating lime and biodegradable flocculants could provide a means of reducing P in greenhouse wastewater below a 1 mg·L−1 regulatory limit in a settling time of less than 30 minutes, while simultaneously recovering P and other nutrients in a form that could be reused as fertilizer. An evaluation of viability of full-scale application of this technology is now warranted.

Flocculation and adsorption properties of biodegradable gum-ghatti-grafted poly(acrylamide-co-methacrylic acid) hydrogels

This study reports the microwave-assisted synthesis of gum-ghatti (Gg)-grafted poly(acrylamide-co-methacrylic acid) (AAm-co-MAA) hydrogels for the development of biodegradable flocculants and adsorbents. The synthesized hydrogels were characterized using TGA, FTIR and SEM. TGA studies revealed that the synthesized hydrogels were thermally more stable than pristine Gg and exhibited maximum swelling capacity of 1959% at 60°C in neutral pH. The optimal Gg-cl-P(AAm-co-MAA) hydrogel was successfully employed for the removal of saline water from various petroleum fraction–saline emulsions. The maximum flocculation efficiency was achieved in an acidic clay suspension with a 15mg polymer dose at 40°C. Moreover, the synthesized hydrogel adsorbed 94% and 75% of Pb2+ and Cu2+, respectively, from aqueous solutions. Finally, the Gg-cl-P(AAm-co-MAA) hydrogel could be degraded completely within 50 days. In summary, the Gg-cl-P(AAm-co-MAA) hydrogel was demonstrated to have potential for use as flocculants and heavy metal absorbents for industrial waste water treatment.

Synthesis and flocculation properties of gum ghatti and poly(acrylamide-co-acrylonitrile) based biodegradable hydrogels

This article reports the development of biodegradable flocculants based on graft co-polymers of gum ghatti (Gg) and a mixture of acrylamide and acrylonitrile co-monomers (AAm-co-AN). The hydrogel polymer exhibited an excellent swelling capacity of 921% in neutral medium at 60°C. The polymer was used to remove saline water from various petroleum fraction-saline water emulsions. The flocculation characteristics of the hydrogel polymer were studied in turbid kaolin solution as a function of the amount of polymer and the solution temperature and pH. Biodegradation studies of hydrogel polymer were conducted using the soil composting method, and the degradation process was constantly monitored using scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results demonstrated an 89.47% degradation of the polymer after 60 days. Finally, the hydrogel polymer adsorbed 98% of cationic dyes from the aqueous solutions.

Biodegradable flocculants based on polyacrylamide and poly(N,N-dimethylacrylamide) grafted amylopectin

Synthesis of amylopectin grafted polyacrylamide (AP-g-PAM) and poly(N,N-dimethylacrylamide) (AP-g-PDMA) was carried out by Ce4+ in water medium. The reaction conditions for maximum grafting was optimized by varying the reaction variables, including the concentration of monomers, ceric ammonium nitrate (CAN), amylopectin, reaction time and temperature. The graft copolymers were characterized by FTIR spectroscopy, NMR (both 1H and 13C) spectroscopy, molecular weight determination and molecular weight distribution by using size exclusion chromatography (SEC), thermal analysis (TGA), SEM studies. Biodegradation of the graft copolymers was carried out by enzyme hydrolysis. Flocculation performances of the graft copolymers were evaluated in 1.0wt% coal and 1.0wt% silica suspensions. A comparative study of the flocculation performances of AP-g-PDMA and AP-g-PAM was also made. It shows that the flocculation performance of AP-g-PDMA was better than that of AP-g-PAM. AP-g-PDMA performed best when compared with other commercial flocculants in the same suspensions.