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A pH-responsive amphoteric starch derivative (PRAS) bearing dual functional groups (amino and carboxyl groups) was prepared through etherification of starch with 2-chloro-4,6-diglycino-[1,3,5]-triazine. PRAS exhibits a reversible pH-response property in aqueous solution. The attractive property of PRAS is that it could be used as an effective flocc...
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... Regenerating the flocculant by de-coagulating the metal ions and maintaining it in its initial state is important as it helps reduce processing costs and enables the removal of heavy metals from the regenerated effluents for recycling. However, there are challenges associated with reclaiming the flocculant, including: (1) Increased likelihood of flocculants and heavy metals binding together, which necessitates the elimination of charges, formation of polymer links, and electrostatic interactions; (2) Difficulty in separating the flocculant from the regenerated solution, as commercially available flocculants tend to be more soluble in water and lack sufficient hydrophilic and lipophilic stability on the polymer chain; and (3) Enhanced binding potential between flocculants [189]. Appropriate flocculants can aid in removing heavy metals from suspended solid substrates or colloidal elements. ...
Pollution is a significant problem in both industrialized and developing countries, as well as in some developed countries. Heavy metal pollution poses a crucial concern for communities due to its detrimental impact on human health and the long-term well-being of the planet. Heavy metals, such as cadmium, chromium, arsenic, lead, and mercury, do not degrade and can enter the food chain, leading to significant health risks. Therefore, it is essential to monitor and take necessary steps to eliminate heavy metal residues that may be present in food, beverages, and the environment. Although the exact role of nanomaterials in pollution cleanup is still unclear, nanotechnology holds promise as a future solution. In the first part of this comprehensive review, a brief overview of nanoremediation is provided. The subsequent sections delve into various nanomaterials and their potential applications in different pollution cleanup scenarios. Following that, critical analysis is conducted on different nano-remediation methods, including oxidation, adsorption, chemical precipitation, filtration, ion exchange , coagulation-flocculation, and photo-catalysis. Lastly, further suggestions are put forward regarding the future utilization of nanotechnology for more effective and enduring pollution cleanup, particularly in eliminating heavy metals.
... Recently, a renewable and chemically-modified starch-based flocculant has also been reported for recycling dyes from textile effluents, suggesting that this concept could also be applied to bioflocculants. 26 Furthermore, studies have shown that some synthetic flocculants are both reusable and effective in reducing the costs associated with the overall flocculation process, 27,28 thus indicating that this concept could also be incorporated into bioflocculants. We conducted three cycles of decolorization/regeneration processes. ...
In this study, the decolorization of anionic dyes was investigated using a novel pH‐responsive bioflocculant (named BF‐TWB10) derived by Bacillus thuringiensis. The BF‐TWB10 showed a dye removal capacity of 99.06% for C.I. Direct Red 224 (DR 224) and 99.22% for C.I. Acid Black 172 (AB 172) at pH 2.0. Its dye removal capacity decreased with increasing pH and the zeta potential analysis revealed that the dye particles exhibited stronger dispersion forces at higher pH levels. Owing to this pH‐responsive property, BF‐TWB10 could be utilized to recover anionic dyes. The recovery rate was 83.46% for DR 224 and 76.46% for AB 172. We then attempted to concentrate the regenerated dye solutions by regenerating the dye‐loaded floc in one‐tenth of its original volume. The concentration multiple of the regenerated dye solutions reached 8.220 and 7.758 times for DR 224 and AB 172, respectively. In addition, the recovery rate of both dyes increased after three cycles of decolorization/regeneration. The results suggested that BF‐TWB10 has potential not only to remediate dyes from textile effluent but also to recover dyestuffs.
... Therefore, the flocculation induced by Cu 2+ was enhanced with increasing Cu 2+ concentration. Many researchers have used this principle of adding anionic flocculants to liquid phases containing heavy metals, such as Cu 2+ (Wu et al., 2018;Chaouf et al., 2019), to remove heavy metals. ...
With societal development, the growing scale of engineering construction, and the increase in environmental protection requirements, the necessity of engineering waste mud disposal is becoming increasingly prominent. In this study, microbially induced struvite precipitation (MISP) was introduced to treat engineering waste mud. The study mainly focused on: i) the optimal mineralization scheme for microbially induced struvite precipitation, ii) the feasibility of the process and the effect of reaction parameters on treating engineering waste mud with microbially induced struvite precipitation, and iii) the mechanism of microbially induced struvite precipitation in treating engineering waste mud. The results showed that the waste mud could be well treated with 8.36 × 10 6 c e l l ⋅ m L − 1 bacteria, 10 mM urea, 20 mM phosphate buffer, and 25 mM M g C l 2 at pH 7. The kaolin suspension could be effectively flocculated. The flocculation rate reached approximately 87.2% under the optimum mineralization conditions. The flocculation effect was mainly affected by the concentrations of reactants and heavy metals and the suspension pH. The X-ray diffraction (XRD) patterns showed a strong struvite (MAP) diffraction peak. Scanning electron microscopy (SEM) images indicated that under the optimal mineralization conditions, the crystals were large and showed prismatic shapes tilted at both ends with adhered kaolin particles. In summary, this manuscript provides an effective way to treat engineering waste mud, and the findings should have a positive effect on enhancing soil fertility and preventing secondary pollution.
... In addition, the pH value of sewage has a great influence on removing heavy metal ions by biopolymer-based flocculants. The lower the pH is, the less favorable it is for biopolymerbased flocculants to remove heavy metal ions Yang et al. 2018;Wu et al. 2018). In the low pH condition, some functional groups on biopolymer-based flocculants were protonated, and positive charges were accumulated on the molecular chain. ...
Biopolymer-based flocculants have become a potential substitute for inorganic coagulants and synthetic organic flocculants due to their wide natural reserves, environmental friendliness, easy natural degradation, and high material safety. In recent years, with more and more attention to clean technologies, a lot of researches on the modification and application of biopolymer-based flocculants have been carried out. The present paper reviews the latest important information about the base materials of biopolymer-based flocculants, including chitosan, starch, cellulose, and lignin etc. This review also highlights the various modification methods of these base materials according to reaction types in detail. Via the recent researches, the flocculation mechanisms of biopolymer-based flocculants, such as adsorption, bridging, charge neutralization, net trapping, and sweeping, as well as, some other special mechanisms are comprehensively summarized. This paper also focuses on the water treatment conditions, the removal efficiency, and advantages of biopolymer-based flocculants in applications. Further, this review sheds light on the future perspectives of biopolymer-based flocculants, which may make progress in the sources of base materials, modification processes, multi-function, and deepening application researches. We believe that this review can guide the further researches and developments of biopolymer-based flocculants in the future, to develop them with a higher efficiency, a lower cost, more safety, and multi-function for more diversified applications.
Graphical abstract
... Proton signals, at 3.80 ppm of the methylene group of -CH 2and COO − are observed. Wu et al. (2018) Starch Grafted With Toluene Poly(propylene oxide) Diisocyanate ...
The exploration of effective natural coagulant materials has never been ceased despite the superiority of synthetic and metallic coagulants. Numerous research outputs have been reported by many extensive studies using a wide variety of natural precursors for water clarification. The current paper outlines the scattered findings on factors affecting the performance of various natural coagulants on coagulation and flocculation activities as well as the mechanisms governing the process. The recent discoveries on the antimicrobial components and bactericidal ability of several natural coagulants are also included. Since starch has received outstanding attention as a promising coagulant and flocculant, the present paper also discusses the latest progress in starch modification techniques applied to enhance the properties of the material for the application as a water treatment agent. The article also recommends an unconventional method for starch modification to produce a greener and sustainable starch coagulant. In assisting the evaluation of a successful modification procedure, the review also presents the research outcomes on modified starch morphological characterization and physicochemical compositions. The research gaps in the existing literatures and several recommendations are addressed in this work to provide a platform for improvement and establish a new promising direction that can be further explored in the development of starch coagulants as an alternative to chemical coagulants.
... Among the heavy metals, zinc is one of the most used ones which is applied in various industries including electroplating, battery manufacturing, dying, fertilizer and pesticide, herbicides, algicides and etc. [1]. Although zinc is essential element for human, it become toxic as exceeds its tolerance level [2][3][4]. Hence, discharging zinc into the environment have detrimental effect on human health as well as the ecosystem. So, it is of great importance to remove it from the industrial effluents even at low concentration. ...
The comparative sorption studies were carried out to investigate the performance of keratin nanoparticles (KNPs) and magnetic KNPs (MKNPs) for Zn(II) uptake. MKNPs showed remarkably higher Zn(II) removal due to the lower keratin weight percent in its structure (8.4%). MKNPs revealed relatively uniform Zn(II) removal within pH range between 4.0 to 6.0 at the temperature of 25°C rather than KNPs. Both KNP and MKNP exhibited two-stage kinetic behavior and reached to their equilibrium adsorption capacity within 30 min. The adsorption of Zn(II) on KNPs and MKNPs followed pseudo second order kinetic model. It was found that the experimental data were best fitted to Sips or Redlich-Peterson isotherm when KNP was used as biosorbent. Unlike KNP, MKNP conformed better to Langmuir model. The maximum adsorption capacity of MKNP at two doses of 3.0 and 5.0 g/L was calculated to be 30 and 18 mg/g, respectively. As the dosage of MKNP raised from 3.0 to 5.0 g/L, the value of KL increased from 0.045 L/mg to 0.154 L/mg, confirming more biosorbent tendency to adsorb metal ions.
... Among the heavy metals, zinc is one of the most used ones which is applied in various industries including electroplating, battery manufacturing, dying, fertilizer and pesticide, herbicides, algicides and etc. [1]. Although zinc is essential element for human, it become toxic as exceeds its tolerance level [2][3][4]. Hence, discharging zinc into the environment have detrimental effect on human health as well as the ecosystem. So, it is of great importance to remove it from the industrial effluents even at low concentration. ...
... Many studies have been carried out to treat synthetic wastewater with a high concentration of heavy metals using integrated natural flocculants with polymer content. Wu et al. [6] reported that a pH-responsive amphoteric starch derivative (PRAS) with the presence of methyl ethyl in its polymer structure was used to treat 74 mg/L of synthetic water containing Zn ions in alkaline phase (pH 9). The Zn removal reported was high (91%), but 20 mg/L of PRAS was able to catch one type of heavy metal only. ...
... Furthermore, the hydroxyl and carboxyl functional groups in TBPF could ionize into sodium salt at high pH (alkaline region), thus increasing solubility [16]. Upon increasing pH value, the carboxylic groups on TBPF were progressively deprotonated and reached full dissociation, while the flocculant was dissolved in water because of the high ionizability of the anionic groups, and it formed a more extended conformation [6]. Polymer bridging and charge neutralization took place between the negatively charged TBPF and cationic metal ions, increasing the flocculation efficiency. ...
... However, the removal of all metal ions was more than 95% at pH 10 compared with the use of hydroxide ions alone, which was less than 18%. At a high pH of the metal ion solution, the high concentration of TBPF increased the degree of interchain interaction between the polymer mixture chain and metal hydroxide; thus sufficient polymer aggregate formation occurred [6]. In addition, the content of polymer mixture leached (amylose and amylopectin) in TBPF increase as the concentration increase. ...
High removal of heavy metals using plant-based bioflocculant under low concentration is required due to its low cost, abundant source, and nontoxicity for improved wastewater management and utilization in the water industry. This paper presents a treatment of synthetic wastewater using plant-based Tacca leontopetaloides biopolymer flocculant (TBPF) without modification on its structural polymer chains. It produced a high removal of heavy metals (Zn, Pb, Ni, and Cd) at a low concentration of TBPF dosage. In our previous report, TBPF was characterized and successfully reduced the turbidity, total suspended solids, and color for leachate treatment; however, its effectiveness for heavy metal removal has not been reported. The removal of these heavy metals was performed using a standard jar test procedure at different pH values of synthetic wastewater and TBPF dosages. The effects of hydroxide ion, pH, initial TBPF concentration, initial metal ion concentration, and TBPF dosage were examined using one factorial at the time (OFAT). The results show that the highest removal for Zn, Pb, Ni, and Cd metal ions were 98.4–98.5%, 79–80%, 97–98%, and 92–93%, respectively, using 120 mg/L dosage from the initial concentration of 10% TBPF at pH 10. The final concentrations for Zn, Pb, Ni, and Cd metal ions were 0.043–0.044, 0.41–0.43, 0.037–0.054, and 0.11–0.13 mg/L, respectively, which are below the Standard B discharge limit set by the Department of Environment (DOE), Malaysia. The results show that TBPF has a high potential for the removal of heavy metals, particularly Zn, Pb, Ni, and Cd, in real wastewater treatment.
... The most important actuates of stimuli responsive polymers are Ph [5][6][7], temperature [8][9][10][11][12][13] and ionic strength [14][15][16][17]. pH responsive polymers show abrupt phase transitions even with mild changes in pH. ...
This work focuses on facile synthesis of pH responsive diblock copolymers based on acrylamide (AM) and 2-Acrylamido-2-methyl-1-propane sulfonic acid (AMPS) grafted on β-Cyclodextrin and have application in solid/liquid separation. β-CD based chain transfer agent (CTA) has been synthesized by one pot synthesis method. Three different grades of β-Cyclodextrin based Macro CTA were synthesized through RAFT polymerization technique. Macro CTA have been used further in synthesis of five different grades of β-CD grafted pH-responsive diblock copolymers i.e. (β-CD-PRP’s) by varying the amount of AMPS. The polymeric materials were characterized by Fluorescence Spectroscopy, FT-IR, GPC, 1H-NMR, SEM, TEM, TGA, and XRD. β-CD-PRP’s shows their micellization properties at acidic pH < 6.57 with polymer conc. > 0.336 mg/mL and has also been studied for removal of model contaminant (kaolin). Among all grades of diblock copolymers, grade 3 shows best performance in the removal of kaolin from aqueous solution at 7 and 5 pH values.
Graphical abstract
... A variety of flocculants are currently useful in wastewater treatment. Every flocculant acts by gaining weight and causing solid particles to separate out from aqueous suspension, leaving it cleaner [5][6][7]. It is well known that turbidity is a measure of the quantity of suspended colloidal particles in water. ...
Alum and other inorganic coagulants have been in use for water treatment since time immemorial. However, exposure to the consecutive metal ions results in chronic effects, the well known of which is Alzheimer’s disease. Alternatives to these coagulants are biopolymer based graft copolymer as flocculant. They are required in minute dosage, non-toxic and are eco-friendly. In this study, alginic acid based graft copolymers have been synthesized via conventional and microwave based technique. Molecular characterization of synthesized graft copolymers have been carried out via standard physicochemical techniques. A comparative investigation of flocculation performance of alginic acid derivatives [synthesized by both the methods i.e., Alg-g-PAM(C) and Alg-g-PAM(M)] and coagulation efficacy of alum has been accomplished in various model suspensions via standard jar test procedure. As anticipated, the flocculation efficacy of Alg-g-PAM(M) has been found much higher than that of Alg-g-PAM(C). Further, the synthesized derivatives exhibited excellent capability in reduction of pollutant load including toxic metal ions removal from wastewater.
