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Understanding the adsorption of polymers onto particles is crucial for many technological and biomedical applications. Even though polymer adsorption on particles is a dynamic process, most experimental techniques can only study the adsorption indirectly, in equilibrium and on the ensemble level. New analysis methods are required to overcome these limitations. We investigated the use of single-particle electrophoresis to study the adsorption kinetics of cationic polymers onto anionic particles and compared the resulting data to a theoretical model. In this approach, the electrophoretic mobility of single polystyrene (PS) particles, exposed to different concentrations of poly(2-guanidinoethyl methacrylate), was measured as a function of time. The polymer adsorption leads to an electrophoretic mobility change of the PS particle over time, from the initial negative value to a positive value at equilibrium. By fitting the kinetics data to the Langmuir model, the adsorption rate, desorption rate and equilibrium constant were determined. Finally, the adsorption kinetics of several other polymers was investigated. This showed that the presented technique enables direct analysis and comparison of the kinetics of polymer adsorption on the single-particle level. This article is protected by copyright. All rights reserved.

This study proposes a new method using the combination of flocculation and prefabricated horizontal drain (PHD) assisted with vacuum pressure for rapid dewatering of high-water-content dredged slurry. First, to demonstrate the superiority of using PHD over the more commonly used prefabricated vertical drain (PVD), experiments were conducted to compare the dewatering performance between the PHD and the PVD. Then six model tests with the proposed dewatering method were performed with various contents of flocculant (anionic polyacrylamide (APAM)) to investigate the effect of APAM content on the dewatering process and soil properties (i.e. undrained shear strength, permeability and compressibility). Furthermore, particle size distributions of the slurry before and after model tests were measured to analyze the dewatering behavior and changes in material properties. Finally, particle loss during vacuum consolidation for various APAM contents were compared to study the flocculation effect on clogging problem. Results indicate that the proposed method can prevent significant bending deformation of the drain board and mitigate clogging of the drain filter and, thus, can significantly accelerate the dewatering process of high-water-content dredged slurry.

Manganese ion (Mn2+) generated from metallurgical, steel making and chemical industries enters sewage treatment plants and affects the sludge activity and flocculation. The effect of Mn2+ on the removal of chemical oxygen demand (COD) and total phosphorus (TP) and sludge activity were investigated in anoxic zone of an anaerobic/anoxic/oxic (A2O) process. The compositions and structures of extracellular polymeric substances (EPS) were characterized using three-dimensional excitation emission matrix fluorescence spectroscopy (3D-EEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to reveal the relationship among Mn2+, EPS and sludge flocculation. The results showed that low concentration of Mn2+ ( 10 mg/L) hindered microbial flocculation and reduced removal efficiencies of the pollutants. When Mn2+was 5 mg/L, removal efficiencies of COD and TP reached 65% and 90%, respectively. Sludge flocculation was the best and SVI was 70.56 mL/g. The changes of Mn2+ concentration caused deviation of groups’ compositions in LB-EPS and TB-EPS, where the main components were always protein (PN) and polysaccharide (PS). The addition of Mn2+ resulted in the degradation of humic acids. However, it did not give rise to significant morphology changes of EPS.

A B S T R A C T This laboratory study examines the potential use of an anionic polyacrylamide (PAM)-based material as an environmentally sustainable additive for the stabilization of an expansive soil from South Australia. The experimental program consisted of consistency limits, sediment volume, compaction and oedometer cyclic swell–shrink tests, performed using distilled water and four different PAM-to-water solutions of PD = 0.1 g/L, 0.2 g/L, 0.4 g/L and 0.6 g/L as the mixing liquids. Overall, the relative swelling and shrinkage strains were found to decrease with increasing number of applied swell–shrink cycles, with an ‘elastic equilibrium’ condition achieved on the conclusion of four cycles. The propensity for swelling/shrinkage potential reduction (for any given cycle) was found to be in favor of increasing the PAM dosage up to PD = 0.2 g/L, beyond which the excess PAM molecules self-associate as aggregates, thereby functioning as a lubricant instead of a flocculant; this critical dosage was termed ‘maximum flocculation dosage’ (MFD). The MFD assertion was discussed and validated using the consistency limits and sediment volume properties, both exhibiting only marginal variations beyond the identified MFD of PD = 0.2 g/L. The accumulated axial strain progressively transitioned from ‘expansive’ for the unamended soil to an ideal ‘neutral’ state at the MFD, while higher dosages demonstrated undesirable ‘contractive’ states.

The present study reports the effectiveness of natural plant materials - fenugreek as a coagulant, with okra and Aloe vera as flocculants, to treat palm oil mill effluent (POME). The treatment process was modelled using Central Composite Design (CCD) of the Design Expert software. Standard jar tests were used to determine the important treatment parameters such as pH, coagulant dosage and flocculant dosage on the removal efficiencies and they were optimized with Response Surface Methodology (RSM). The optimum condition obtained from RSM was established for pH, coagulant dosage and flocculant dosage as pH 4, 22.24 g/L and 16.77 mL/L respectively for fenugreek-okra, and pH 4, 24.13 g/L and 20 mL/L respectively for fenugreek-Aloe vera. Removal efficiencies of TSS, TUR and COD were 88.19%, 78.35% and 30.56% respectively for fenugreek-okra and 83.40%, 82.78% and 32.95% respectively for fenugreek-Aloe vera. Results obtained from characterisation shows that the coagulation – flocculation process was ruled by inter-particle bridging as the dominant mechanism.

Concerns about the concentration of organic dyes in wastewater have been raised by environmentalists for quite some time. Many industries, including fabric, food, makeup, and paper industry, are significant sources of organic dye disposal in wastewater. This is creating a significant problem for many organisms which are living in water. Various methods reported till date for organic dyes removal from water are divided into chemical, physical, and biological methods. As different dyes are used in different industries, distinct methods are used for their effective removal. Different physical methods for removing dyes include adsorption, coagulation/flocculation, and filtering. Electro-Fenton, Photocatalysis, and Ozonation are examples of chemical techniques. The biological methods include the use of enzymes and microbes, as well as biosorption and biodegradation.

The selective removal characterization of colloids in petrochemical secondary effluent treated by coagulation-flocculation (CF) coupled with persulfate (PS) process was investigated. Results showed that the optimal dosages for CF-PS were as follows: poly aluminium chloride (PAC) of 25.0 mg/L, Fe2+ of 6.0 mmol/L, Na2S2O8:12COD ratio of 1.0, and the removal ratio of dissolved organic carbon (DOC) reached 55.0%. The order of importance of factors affecting efficiency was as follows: Fe2+, S2O82−, pH, and the DOC removal followed the pseudo-first-order kinetic model. Ultrafiltration technology was used to analyze the distribution of different molecular weights (MWs) in colloids, and to investigate the selective removal of colloids. CF-PS can effectively remove high-MWs (> 50 K) colloids, with its DOC removal of 41.3%. Single PS can effectively remove medium-WMs (3 K~50 K) and low-MWs (< 3 K) colloids, with the DOC removals of 62.7% and 40.3%, respectively. Excitation emission matrix fluorescence spectroscopy combined with fluorescence regional integration analysis indicated that the medium-MWs and low-MWs fractions were removed more in the fulvic acid-like, soluble microbial metabolites, and humic acid-like substances by the PS process. Moreover, with the addition of CF pretreatment, CF-PS enhanced the removal of high-MWs and medium-MWs in the tyrosine-like and tryptophan-like substances. The relationship between the fluorescence and the DOC further reveals that humic acid-like/soluble microbial metabolites substances are dominant contributors to colloidal organic carbon in the CF-PS. This study provided a new approach to evaluate the selectivity of colloids during PS-related processes and AOPs.

The rapid growth of population with increased facilities for comfort nowadays leads to a drastic depletion of natural resources. The present work emphasizes the re-refining process of waste lubricating oil by the solvent-extraction flocculation process. Re-refining is considered by many as a preferred option in conserving resources, minimizing waste, and reducing environmental hazards to a great extent. The effect of various parameters like refining time, refining temperature, solvent to waste oil ratio, flocculant dosage, adsorbent to distilled oil ratio has been elaborately studied, and the optimum yield percent was obtained at 33 °C of refining temperature, 20 min of refining time with a solvent to waste oil ratio of 5:1 (w/w). Various solvents like iso-butanol and n-butanol were used, and iso-butanol was found to produce a higher yield of 72%, which is 2% higher than the solvent n-butanol. Calcium hydroxide was used as a flocculant, and a concentration of 2 kg of flocculant per kg of solvent was optimum. The flashpoint, ash content, and viscosity index of re-refined oil were 210 °C, 0.25 g, and 175, respectively, comparable to virgin lube oil. The purity and the existence of oxidation products were elaborately analyzed by FTIR and GC–MS analysis. Thus, the refined oil obtained can effectively mitigate the ever-growing oil crisis and help create a healthy and pollution-free environment.

In this paper, an effective and sustainable treatment method for recycling chromium from sludge produced by magnetic flocculation was established. Chromium was extracted from sludge with hydrogen peroxide and sodium hypochlorite, and then, superparamagnetic ferroferric oxide nanoparticles (MPs) were recovered by magnetic separation. The recovery percentage of chromium with sodium hypochlorite was higher than that with hydrogen peroxide, and the maximum was 99.12%. With increasing MPs use times, the adsorption percentage of chromium decreased, but there was no significant change in the recovery percentage of chromium in sludge. The purity of the recovered sodium chromate crystals was 96.28%. The back-propagation algorithm was used to model chromium recovery. The correlation coefficient between the model prediction data and experimental data was 0.9990, and the average absolute error was 0.51. The maximum recovery percentage of chromium obtained from model prediction was 99.27%, and the corresponding optimal conditions were consistent with those of experiments.

Waste biomass of Pichia pastoris (P.pastoris) cells from the fermentation industry is an environmentally friendly biosorption material. The present study aimed to explore the biosorption behaviour of waste P.pastoris cells for Cu(II), Ni(II) and Cr(VI) in aqueous solution conditions. The results showed that the adsorption kinetics of three kinds of metals were well-fitted with lineared Elovich, pseudo-second-order kinetics models, non-linear kinetics and adsorption isotherms. The effective biosorption rates for Cu(II), Ni(II) and Cr(VI) removal were 71.3%, 59.7% and 16.25% respectively. The maximum Cu(II) adsorption capacity of waste P.pastoris was 40 mg/g at pH = 4 and 225 mg/L of solute concentration for 0.4 g biomass, better than that of the living yeasts. The pattern of Fourier transform infrared (FTIR) indicated that functional groups such as –NH, –OH, Si–O, P–O–C were involved in Cu(II) adsorption process. The analysis of SEM-EDS, XRD and TEM-EDS can be concluded that Cu(II) occupied Ca(II) binding sites by ion exchange mechanism to remove flocculation, and Cu(II) adsorbed onto the diatomite containing in the industrial waste P.pastoris. Thus the adsorption mechanism of the industrial waste P.pastoris was proposed taking Cu(II) as the example. And consecutive biosorption/desorption cycles were used for the evaluation of the regeneration efficiency, suggesting the good regeneration and reusability of waste P.pastoris.

This study investigated the efficacy of using micro-flocculation as a pretreatment approach in alleviating ultrafiltration (UF) membrane fouling caused by organic matter in treated wastewater. Three typical model dissolved organic matters (DOM), humic acid, fulvic acid, and sodium alginate, were employed to simulate membrane fouling. The results showed that micro-flocculation using poly aluminum chloride (PAC) or polymerized ferric sulfate (PFS) as flocculant could effectively enhance the treatment performance of the UF process on DOM. With 6 mg/L PAC, the removal efficiency of humic acid, fulvic acid, and sodium alginate by micro-flocculation combined UF process reached 79.95%, 63.25%, and 51.14%, respectively. Specifically, after micro-flocculation, micromolecular hydrophilic organic matter (e.g., fulvic acid) tended to form a compact cake layer. The macromolecular hydrophobic organic matter (e.g., humic acid) and macromolecular hydrophilic organic matter (e.g., sodium alginate) generally led to a loose cake layer. At PAC dosage of 6 mg/L, the membrane specific flux (J/J0) at the end was improved by 11.71%, 10.27%, and 2.2% for humic acid, sodium alginate and fulvic acid solutions, respectively, compared with the UF process alone. It could be inferred that micro-flocculation pretreatment can effectively mitigate the membrane fouling when treating wastewater containing humic acid, sodium alginate, or fulvic acid. HIGHLIGHTS Micro-flocculation could enhance the capability of the UF process in removing DOM.; Micro-flocculation pretreatment effectively alleviated UF membrane fouling.; Cake layer played an important role in mitigating UF membrane fouling.; The compactness of cake layer was related to the molecular weight, hydrophilicity or hydrophobicity of organic matters.

The use of agricultural waste materials to remove heavy metals from wastewater is attractive due to its simplicity and economic efficiency. In this study, the applicability of calcined eggshell waste materials (CES) for heavy metals removal from real wastewater were examined via transport column experiment preceded by coagulation/flocculation process.A column packed with granular activated carbon (GAC) is operated in parallel to CES column to evaluate the adsorptive attributes of CES. The findings are assessed from another set of column experiments consisting of sand followed by CES column to evaluate the effect of particulate matter (PM) on CES performance toward heavy metals removal. In coagulation experiment, alum addition at an optimum dose (3.0 g/L) reduced the total suspended solids (TSS) by 80%, whereas the Fe, Pb, Zn, Cu, Ni, and Cr were reduced by 80%, 77%, 76%, 73%, 56%, and 49%, respectively. Under the current applied hydrodynamic conditions, using sand column before CES column improved the removal efficiencies of Fe, Pb, Cu, Zn, Ni, and Cr from 50% to 92%, 55% to 93%, 60% to 87%, 53% to 76%, 45% to 65%, and 41% to 60%, respectively. The whole results illustrate that CES can be competitive to GAC for heavy metals removal from landfill leachate, mainly if applied after PM removal by sand filtration. HIGHLIGHTS Total suspended solids and heavy metals are effectively decreased by adding 3.0 g/L alum.; Heavy metals are effectively eliminated from landfill leachate using calcined eggshells.; Particles facilitated heavy metal movement via the filter media.; Sand pretreatment improved the performance of calcined eggshell to remove heavy metals.; The research findings may lead to more cost-effective landfill leachate treatment technology.

The chemical agglomeration technology can effectively remove fine particles during coking coal loading and unloading. Aiming at the traditional agglomerator has the high price and secondary pollution problems, the new method of viscosifying fine particles was established. The fine particles were contacted with the soap solution through the cyclone circumfluence to increase viscosifying and agglomerate. The regulation and control of uniform humidification of whole particles were studied, and the relations among humidification, agglomeration, dust suppression and agglomeration conditions of fine particles were discussed. By establishing the agglomeration model and mechanical model, the influence of agglomeration on the force and velocity distribution of particles was analyzed based on CFD. The results showed that the soap solution has a strong effect on agglomeration of particle size less than 0.5 mm. The adsorption and flocculation of the polymer chain in the soap can promote the agglomeration of the fine particles. In the area of vortex formed by swirling air, with the mass addition ratio of soap powder increases from 5% to 15%, the coating efficiency of fine particles increases from 82% to 96%. The agglomeration results show that the average concentration of the fine particles decreases by nearly 20% finally.

Multiple biogeochemical processes in estuaries modulate the flux of nutrients from land to sea, thus contributing to the coastal filter. The role of particle dynamics in regulating the fate of terrestrial nutrients in estuaries is poorly constrained. To address this issue, we resolved the particle size distribution of suspended material, and quantified size-fractionated particulate nitrogen (PN) and phosphorus (PP), in a stratified mesotrophic estuary (Pojoviken, Finland). We also carried out a mixing experiment where the effects of salt-induced flocculation on particle size distribution and concentrations of PN and PP were examined. The experimental results showed that salt-induced flocculation at already very low salinities increases the total particle concentration and mean particle size, indicating transfer of dissolved material into particulates. Correspondingly, a significant increase in PP and particulate iron (Fe) was observed in the experiment results, suggesting coupled flocculation of P-containing organic matter (OM) and ferrihydrite. Particle dynamics in the field data were dominated by processes occurring downstream of the flocculation zone. Primary production created a downward flux of autochthonous OM particles, promoting passive aggregation by random collisions with terrestrial material in the water column. Maximum particle concentrations were observed at and below the halocline. The highest PN and PP concentrations were observed in the subhalocline layer, 3.5 and 0.14 mu mol L-1, respectively. Molar ratios of N:P in this material were >40, consistent with typical marine snow in the early stages of microbial processing. Our study provides a mechanistic overview of the biogeochemical drivers of particulate nutrient dynamics in stratified estuarine environments.

The focus of the present study was to explore how and to what extent ultrahigh salinity affects the adsorption of cadmium and hydrocarbon pollutants onto aluminum hydroxide adsorbents formed in an electrocoagulation process. The changes in the nature and structure of the electro-generated aluminum particles and the possible removal mechanisms due to high salt content were investigated by using FE-SEM/EDS, FTIR, BET, and XRD analyses. The pseudo-second order and Freundlich models proved to fit the data for cadmium adsorption onto the aluminum hydroxides best. It was demonstrated that the adsorption capacities were significantly affected by the high salinity. With the rise of the salinity from 2 to 170 g/L, the cadmium and COD removal yields dropped from 81 to 60% and from 90 to 72%. The increase of the oil content led to the enhanced cadmium adsorption capacity due to surface complexation and ion exchange mechanisms. It was proved that Lagergren pseudo-first-order kinetic model could justify COD abatement trends. FTIR spectra depicted that the negative impact of high salinities on the adsorption was due to causing the formation of less stable adsorbents. According to BET analysis, the occurrence of much wider pore size distribution and smaller specific surface area in high salinity case was the main reason for the decreased adsorption capacity. Based on XRD analysis, the higher crystallinity of the produced aluminum hydroxide particles and their consequential smaller surface areas resulted in the lower adsorption capacity in the hypersaline environment. It was concluded that adsorption via inner-sphere and outer-sphere complexation and sweep flocculation were the possible removal mechanisms. Total treatment cost of 8.75 and 3.49 €/m3 were estimated for low and ultrahigh salinity conditions.

Selective precipitation of RNA is often used in molecular biology as one of the methods for separation of nucleic acids to obtain samples enriched with DNA or RNA molecules alone or for purification of RNA samples. In the present study a simple and fast approach for selective precipitation of RNA with linear polyacrylamide is proposed for the first time. The method is based on the different predispositions of the DNA and RNA molecules to bind with the polyacrylamide. In this process, the linear polyacrylamide is used as the flocculant, collecting RNA particles to form aggregate, which then precipitated at low alcohol concentration. During and after precipitation the temperature is adjusted to maintain high solubility of DNA and other contaminates at given pH, salt and alcohol concentrations on the one hand, and globular state of polyacrylamide, preventing solubility of the RNA-LPA aggregate, on the other hand. The precipitated RNA can be used directly for RT-qPCR assay. The principal advantage of the present approach is the fast and quantitative precipitation of most RNA species from very dilute solutions. This makes it possible to obtain both almost DNA-free RNA and RNA-free DNA samples in one process.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.2007397 .

Most dyes are complex organic molecules that are highly resistant to degradation and may cause severe damage to live organisms and photosynthetic activities. In this respect, the aim of the present...

An inorganic-biopolymers hybrid flocculant (PSAC-SA) was prepared by modifying sodium alginate onto polysilicate aluminum calcium (PSAC) through coordination between SA and Ca2+. The preparation conditions of PSAC-SA and the flocculation parameters that influence of the turbidity and color removal efficiency were investigated and optimized. The flocculation experiments results showed that the maximum turbidity and color removal could get 97.2% and 98.4% for kaolin-humic acid suspensions, respectively. The application of PSAC-SA for Songhua River treatment indicated that it had an excellent flocculation capacity in real water samples, and its flocculation efficiency was much better than that of individual flocculants (PSAC and SA). Moreover, the flocculation mechanisms were discussed in detailed, which indicated that the bridging effect and physical entrapment of solid particles played an important role in the flocculation process.

Gravity thickening by deep cone thickener is popularly applied in cemented paste backfill, which is essential for tailings management and green mining. To avoid rake bogging, high concentration and high flowability are required for thickened tailings slurry. These properties depend critically on the yield stress of the slurry. The yield stress, in turn, can be influenced by the flocculant dosage and the acidity (pH) that form the flocculation condition. Experiments have been performed to eventually quantify the dependence of yield stress on these two variables. The yield stress test of flocculated and thickened copper mineral tailings slurry, and the analysis of flocculant adsorption, were conducted at different pH values and flocculant dosages. It turns out that the amount of flocculant adsorbed on the tailings particles surface has a maximum with respect to pH but increases with the increasing flocculant dosage. In turn, the amount of flocculant adsorbed affects the yield stress, a macroscopic property of the slurry, through the total interactions (microscopic) between polymer-coated tailings particles. Bridging interaction is essential for total interactions. It is obtained that the yield stress varies analogously to the absolute of the minimum value of the total interactions at different pH values and flocculant dosages. Therefore, interparticle interactions should be adjusted by control pH and flocculant dosage to achieve high-concentration and high-flowability underflow to avoid rake bogging in a deep cone thickener.

To explain the incompatibility of some superplasticisers with class F fly ash, the effectiveness and mechanisms of superplasticisers based on lignosulfonate (LS), polynaphthalene (PNS) and polycarboxylates (PCE-1 and PCE-2) in dispersing the fly ash pastes were studied. The most effective superplasticisers, PCEs (PCE-1 and PCE-2), produced almost no additional electrostatic repulsion, are adsorbed in low amounts, and exhibited negligible adsorbed layer thickness. It is suggested that the excellent dispersing abilities of PCEs rely on the molecules remaining in the liquid phases of the pastes. For the inefficacy of LS and PNS, the absorption of molecules and bridging flocculation are the most likely causes. Superplasticiser molecules that entered the fly ash through the pores on the fly ash surface lost their dispersing abilities. The highly negatively charged LS and PNS can attract several fly ash particles to form the bridging flocculation, which reduced the dispersion of the fly ash pastes.

A screening programme using mineral salt medium supplemented with n-hexadecane resulted in isolating a Bacillus megaterium SPSW1001 which was capable of producing surface active molecules lowering culture medium surface tension to 27.43 ± 0.029 mN/m and interfacial tension to 0.38 ± 0.03 mN/m at 72 h and an emulsification index (E24) (85.63%). The biosurfactant product was further used to assess its effects on the rheological characteristics of water-in-oil emulsion prepared with engine oil. Structural characterization of the biosurfactant product by FTIR revealed a C–O–C stretch in sugar moiety and ester carbonyl linkage group between sugar and fatty acids, respectively, while mass spectral analysis revealed its glycolipid nature, with an m/z value of 662.44. The fluid behaviour of water-in-oil emulsion showed a non-Newtonian viscoelastic dilatant flow after yielding exemplified appropriately by Herschel-Bulkley model with 100% confidence of fit. The present study is significant in formulation and handling, processing, and transport of emulsion and in understanding flocculation characteristics.

The reuse of fracturing fluid flowback contributes toward water resource conservation and the reduction of environmental pollution. However, the ability to reuse the flowback is affected by its residual boron content. Hence, the control of boron content is crucial for effective flowback reuse and the reduction of relevant treatment costs. In the present study, chemical oxidation combined with the flocculation precipitation method was used to remove residual boron from fracturing flowback fluid. Taking boron removal rate as an index, the effects of the precipitator, oxidant, pretreatment pH (pHp), n(H2O2)/n(B) value, pretreatment time (tp), n(Ba)/n(B) value, reaction pH (pHr), and reaction time (tr) on boron removal by chemical oxygen precipitation were studied. The results showed that boron removal was performed at 20–25 °C via chemical oxidative precipitation. The use of BaCl2 as the precipitating agent and H2O2 as the oxidizing agent (under the following conditions: pretreatment pH = 9, pretreatment time (tp) = 30 min, reaction pH = 10, and reaction time (tr) = 360 min) led to a boron removal rate of 95.5% and a residual boron content of 6.76 mg/L in the solution.

How to efficiently utilize most abundant biomass of cellulose, lignin and their derivatives has become an emerging challenge as the anticipative oil depletion. In this paper, the ternary anionic copolymer of carboxymethyl cellulose-acrylamide-lignosulfonate (CAL) was successfully prepared by hydrothermal polymerization. Based on the flocculation characteristics of cationic methylene blue, the optimal polymerization process was confirmed as the raw material ratio of 1:1:1, initiator dosage of 0.9 wt %, the reaction time was 5 h and the reaction temperature was 55 °C. The results showed that the decolorization ratio was 87.5% at the CAL dosage of 600 mg/L for the 500 mg/L methylene blue simulated wastewater. The CAL achieved fast flocculation kinetics and super color removal ratios in the wide ranges of environmental pH, temperature and salt concentration. The flocculation mechanism is single charge neutralization. Moreover, the estimated treatment cost of CAL is 68.3% lower than that of commercial anionic PAM. The prepared anionic CAL flocculant has the characteristics of environmental safety, excellent flocculation performance and cost-effectiveness, which shows great potential in the field of dye wastewater treatment, and also provides a feasible way for the effective utilization of biomass resources.

Coagulants and flocculants are used almost at all drinking water supply facilities, wastewater treatment plants of municipal and industrial enterprises in Belarus and Ukraine to intensify and increase the efficiency of the processes of purification, clarification and discoloration of water and wastewater. Mainly as coagulants aluminum and iron salts are used, as flocculants - active silicic acid, starch, cellulose derivatives, polyacryloamide, etc. Sulfuric acid treatment of alumina-containing raw materials allows, in the course of one process, to obtain a mixture of active substances - salts of aluminum, iron, active SiO2. In this case, there is no need to separate the salt from suspended particles and colloidal silicic acid. The presence of suspended dispersed particles in the active substance, as well as colloidal silicic acid and its salts, enhances and accelerates coagulation. The resulting solution, along with aluminum sulfate, contains silicic acid, which acts as a flocculant in the process of water purification. In addition, the processed products also contain ferrous sulfate, in the presence of which a better coagulation result is achieved. Industrial tests of the coagulant-flocculant were carried out in order to purify wastewater from oil products. The test results showed that the effectiveness of the coagulant-flocculant in reducing the content of oil products in wastewater is comparable to the currently used aluminum sulfate. The effectiveness of the developed coagulant-flocculant for the purification of drinking water was evaluated in comparative tests with a coagulant “Polvak-68” in the mode of trial coagulation on a laboratory flocculator. The research results are showed that the value of all parameters characterizing the contamination of the source water are highty decreasing for experimental coagulant-flocculant in compare with regular product. Практично на всіх об'єктах питного водопостачання та станціях очищення стічних вод комунальних і промислових підприємств Білорусі й України застосовуються коагулянти і флокулянти для інтенсифікації та підвищення ефективності процесів очищення, освітлення і знебарвлення природних та стічних вод. Як коагулянти використовуються, в основному, солі алюмінію і феруму, а як флокулянти - активна кремнекислота, крохмаль, похідні целюлози, поліакрілоамід тощо. Сульфатнокислотна обробка алюмінійвмісної сировини дозволяє в ході одного процесу отримувати суміш активних речовин - солей алюмінію, феруму та активну SiO2. При цьому немає необхідності відокремлювати солі від завислих часток і колоїдної силікатної кислоти. Присутність в діючій речовині завислих дисперсних частинок, а також колоїдної силікатної кислоти і її солей підсилює і прискорює коагуляцію. Одержаний розчин, поряд з алюмінієм сульфатом, містить також силікатну кислоту, яка в процесі очищення води виконує роль флокулянта. Крім того, серед продуктів переробки є також ферум сульфат, в присутності якого досягається кращий результат коагулювання. Проведено промислові випробування коагулянту-флокулянту з метою очищення стічних вод від нафтопродуктів. Результати випробувань показали, що ефективність коагулянту-флокулянту за умови незначного вмісту нафтопродуктів у стічних водах порівнянна з використовуваним на даний час алюмінієм сульфатом. Ефективність розробленого коагулянту-флокулянту для підготовки питної води оцінювалася в порівняльних випробуваннях з коагулянтом «ПОЛВАК-68» в режимі пробної коагуляції на лабораторному флокуляторі. Результати досліджень показали, що значення всіх параметрів, які характеризують забрудненість вихідної води, за умови використання експериментального коагулянту-флокулянту є значно нижчими в порівнянні зі звичайним продуктом.

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.

Green bio-flocculants from renewable biomass resources have received the widespread attention for wastewater treatment, which are promising alternatives to petroleum-based synthetic flocculants. In this paper, sustainable cationic cellulose bio-flocculants with various amino group contents were successfully prepared by a feasible chemical crosslinking with polyethyleneimine (PEI). The flocculation performances of diverse PEI-grafting cellulose (CE-PEI) were evaluated to purify turbid Kaolin suspension. Further, the flocculation kinetics and flocculation mechanism were investigated. Benefiting from the high surface positive charges and supramolecular structure, CE-PEI bio-flocculants with amino group contents of 17.5 mmol/g displayed the best turbidity removal efficiency. The residual turbidity of Kaolin suspension decreased from the initial 480–8.6 NTU, a 98.2% reduction with CE-PEI dosage of 0.15 mg/mL, sedimentation time of 30 min at pH 7.0. Flocculation kinetic results indicated that interaction of aggregation and collision between CE-PEI bio-flocculants and Kaolin particles was sufficient for the flocculation process at the optimal CE-PEI dosage. Moreover, charge neutralization was the dominant mechanism for the flocculation of CE-PEI on Kaolin. Thus, this work not only exploits a promising application of cellulose as a bio-flocculant, but also provides a feasible approach to efficiently purify high turbidity wastewater.

Kraft lignin is an underutilized material mainly combusted in the pulping industry. Its conversion to value-added products for further end-use applications is limited due to its insolubility in water. In this work, the modification of kraft lignin (KL) was conducted through oxidation and carboxymethylation to generate anionic water-soluble lignin (OKL, and CMKL, respectively). The results indicated that these biopolymers acted as effective dispersants in an aluminum oxide suspension. Subsequently, generated biomaterials were polymerized with acrylamide monomer to generate flocculants (i.e., OKL-AM and CMKL-AM) for the aluminum oxide suspension. The properties of polymers were characterized extensively, and the polymerization of OKL and CMKL with acrylamide increased the molecular weight (Mw) of the biomaterials from 16 × 103 and 28 × 103 to 684 × 103 and 387 × 103 g/mol, respectively. Flocculation studies under stirring revealed that the chord length of aluminum oxide particles increased substantially by treating the suspension with the OKL-AM polymer. The reflocculation analysis provided further insight into the reversibility and high strength of formed flocs. Our results confirmed that by following a one-step reaction, a lignin-based dispersant could be generated, and further polymerizing the biomaterials (i.e., dispersants) would make it a valuable flocculant. This investigation confirms a versatile and environmentally friendly pathway to convert a waste material (i.e., lignin) to a green dispersant and flocculant.

A new kind of micro-electrolysis filler sewage sludge biochar/zero valent iron (SSBC/ZVI) composite was prepared for a real chemical synthesis based pharmaceutical wastewater pretreatment for improving the biodegradation index (BI). The optimal operation condition of micro-electrolysis system was obtained at HRT of 2 h, the initial pH of 3.0 and filler dosage of 100 g/L, with COD removal rate of 30.5%. Characterization analysis of raw/used SSBC/ZVI filler and GC–MS analysis of raw/treated pharmaceutical wastewater were conducted to reveal the pollutant removal mechanisms by micro-electrolysis, and the results suggested that the pollutants removal was mainly attributed to the combination of reduction and oxidation, absorption of SSBC and flocculation of iron sludge. SSBC/ZVI exhibited relative high stability and excellent reusability for COD removal and BI improvement of real pharmaceutical wastewater after 4 runs. Moreover, the leaching tests of heavy metals (HMs) were conducted to investigate their release of the constituents in SS, and the results indicated that HMs leaching into the liquid from the filler was at a relative low level. This study provided new ideas of sewage sludge utilization for real wastewater pretreatment.

Carwash wastewater treatment with potassium ferrate (VI) (K2FeO4) was optimized by response surface methodology. The optimum conditions for chemical oxygen demand removal were established a pH 3.5, 0.328 g/L dose of K2FeO4, and with a process duration of 48 min. At these conditions, chemical oxygen demand, total organic carbon, total nitrogen, and total phosphorus decreased by 70.3, 58.9, 73.3, 82.0%, respectively; and the putrid odor was reduced. Simultaneously, the total viable count, total coli count, most probable number of fecal enterococci, and the total proteolytic bacteria count decreased by 89.5, 93.1, 92.9, and 95.0 %, respectively. Comparatively, an application of 0.450 g/L FeCl3·6H2O corresponding to the iron content in 0.328 g/L of K2FeO4 resulted in a decrease of total viable count, total coli count, most probable number of fecal enterococci and the total proteolytic bacteria count only by 38.1, 31.2, 42.9, and 58.0%, respectively. Therefore, flocculation with polyacrylamide anionic flocculant combined with potassium ferrate (VI) oxidation is a more effective alternative to coagulation with FeCl3 and the same flocculant. The use of potassium ferrate (VI) is a viable option for the treatment of carwash wastewater.