Influence of centrifugal flow conditions and flocculation parameters on fine particle recovery

The removal of Reactive Black 5 dye in an aqueous solution by electrocoagulation (EC) as well as addition of flocculant was investigated. The effect of operational parameters, i.e. current density, treatment time, solution conductivity and polymer dosage, was investigated. Two models, namely the artificial neural network (ANN) and the response surface method (RSM), were used to model the effect of independent variables on percentage of dye removal. The findings of this work showed that current density, treatment time and dosage of polymer had the most significant effect on percentage of dye removal (p<0.001). In addition, interaction between time and current density, time and dosage of polymer, current density and dosage of polymer also significantly affected the percentage of dye removal (p=0.034, 0.003 and 0.024, respectively). It was shown that both the ANN and RSM models were able to predict well the experimental results (R(2)>0.8).

The precipitated calcium carbonate (PCC) flocculation kinetics and floc structures induced by cationic tapioca starch were recorded by the Malvern Mastersizer 2000 (Malvern Instruments Inc, Malvern, UK). Of particular interest, a population balance model for PCC flocculation was employed to extract the flocculation constants, namely collision efficiency, magnitude of energy dissipation rate and restructuring rate. The model made an attempt to take aggregation, breakage and flocs restructuring into account simultaneously to describe the PCC flocculation by aggregation and breakage mechanism. Through a response surface methodology (RSM) involving a central composite design, the effects of temperature, polymer dosage, ionic strength, and shear rate on flocculation parameters were investigated in this paper.

The effect of colloid concentration and pH on kaolin suspensions flocculated with cationic polyacrylamides of high molar mass

In Canada’s oil sands industry, the processing and storage of fluid fine tailings is important because it directly impacts land usage and reclamation, water and thermal energy requirements as well as environmental stewardship and mine sustainability. A key technology used for this purpose is inline flocculation, wherein existing inventories of fluid fine tailings are withdrawn from tailings storage facilities and mixed with polymer flocculants. These flocculated tailings can be then sent through additional process stages (e.g. evaporation, centrifugation, filtration) to promote dewatering and improved geotechnical characteristics of the resulting deposits. The polymer type, dosage and inline mixing conditions primarily dictate the efficacy of the inline flocculation process. Presently, numerous measurements are taken to establish flocculation performance. Some of these require samples to be collected and analyzed, meaning that such measurements cannot be used for real-time process control. Others, such as online FBRM (focus beam reflectance measurement), can be used for real-time process control but are often challenging and expensive to deploy in a commercial operation. The present study represents a preliminary assessment of the use of pressure measurements to monitor flocculation performance using a pilot-scale inline flocculation rig. Tests were conducted at different flow rates and polymer injection rates/concentrations. The test rig was fitted with 4 differential pressure sensors positioned at different axial locations. The pressure gradients measured just downstream of the inline mixer were primarily dictated by the production, and subsequent break-up, of the shear-sensitive floc structures and thus were highly sensitive to changes in polymer dosage at any given fluid tailings feed rate. A relationship among conventional performance metrics (e.g. floc size from FBRM) and maximum pressure gradient measured downstream of the mixer was observed, i.e. the same optimal polymer dosage was indicated by conventional measures and peak pressure gradient.

Design and synthesis of a new magnetic molecularly imprinted polymer nanocomposite for specific adsorption and separation of diazinon insecticides from aqueous media

Using sulfide ore and oxide ore tailings of a tin mine in Yunnan as raw materials, 17 groups of flocculation settling tests were designed by Box‐Behnken in Design‐Expert software, and the settling velocity and underflow concentration of mixed tailings with sulfur/oxygen ratio of 5 : 5 were studied. The effects of volume concentration, flocculant unit consumption, and flocculant concentration on settling velocity and underflow concentration were explored, and the optimal parameters of settling velocity and underflow concentration were obtained. Results. The best mixing parameters of mixed tailings are volume concentration of 17.66%, flocculant unit consumption of 39.589 g/t, and flocculant concentration of 0.195%. At this time, the settling speed is 2.231 mm/s and the underflow concentration is 65.289%. The flocculation settling velocity under this parameter condition was tested, and the experimental results were consistent with the predicted results of the model. This surface method can be used to design the flocculation and settlement test of mine tailings, which has certain guiding significance for the selection of parameters in actual production of mines.

Response surface optimization of chemical coagulation for solid–liquid separation of dairy manure slurry through Box–Behnken design with desirability function

pH dependence of bentonite aggregate size and morphology on polymer-clay flocculation

Treatment of heavy metal polluted industrial wastewater by a new water treatment process: ballasted electroflocculation

Design of SiO2-TiO2-PAM composite flocculant with self-degrading characteristics and optimization of the flocculation process using a combination of central composite design and response surface methodology

This paper presents the effect of the structure of cationic polyacrylamides (CPAMs) on flocculation of pulp suspensions and floc properties. A focused beam reflectance measurement (FBRM) probe was used to monitor flocculation, deflocculation, and reflocculation processes in real time. To carry out the study, 1% elemental chlorine free (ECF) eucalyptus kraft pulp containing 20% ground calcium carbonate (GCC) was used. Results show that the effect of the CPAM structure depends on charge density and polymer dose. Floc size does not always decrease with branching degree, whereas floc stability and reflocculation ability increased when highly charged and branched CPAM was used. These findings indicate that the use of highly branched CPAMs with very high molecular weight is very promising as a retention aid method to improve the papermaking process.

The effect of polymer adsorption kinetics and ionic strength on the dynamics of particle flocculation was quantified using a model system consisting of precipitated calcium carbonate (PCC) and cationic polyacrylamide (CPAM) at a low shear rate. All early flocculations detectable by a photodispersion analyzer (PDA) happened in nonequilibrium polymer adsorption regimes. We observed discrepancies in flocculation rates with the surface coverage theory, which is based on a simple monolayer adsorption model, in both early and late flocculation stages. For instance, the same amount of adsorbed CPAM reached at different polymer doses demonstrated different flocculating capabilities. This highlighted the importance of polymer adsorption kinetics upon flocculation. The transient conformation of the adsorbed CPAM during the kinetic process sometimes even superceded the adsorbed amount in the determination of PCC flocculation. Both antagonistic and synergetic effects of increased ionic strength on the CPAM-induced PCC aggregation were observed during early flocculation. However, late-stage PCC flocculation shared some similarities, irrespective of polymer dose and ionic strength. Despite the decreased amount of adsorbed polymer from the increased ionic strength, the combination of CPAM and salt, at certain concentrations, demonstrated a synergy to promote PCC aggregation more efficiently than the same amount of the respective components.

A flocculation process was performed to treat travertine-processing effluents with a high concentration of suspended solids using an eco-friendly biopolymer. The experiments were conducted through a standard jar test procedure to optimize the process parameters for sludge volume index (SVI) and turbidity removal. The effects of mixing time, suspension pH, and polymer dosage on treatment efficiency were investigated using central composite design, a standard technique in response surface methodology. The constructed response model was tested using the analysis of variance (ANOVA). Using the Design-Expert tool, the coefficients of regression models were computed. The Fischer value (F-value) was used to evaluate the significance and validity of the predicted model, while the coefficient of determination (R2) was applied to estimate the model significance by comparing the predicted data with the measured data. The optimized parameters obtained were polymer dose of 276.20 mg/L, suspension pH of 8.60, and mixing time of 4.20 min. The optimal SVI and turbidity values obtained were 1.36 mL/g and 2.99 NTU, respectively. Additionally, R2 values for SVI and turbidity were determined as 0.9337 and 0.8654, respectively. Also, the difference between adjusted R2 values and predicted R2 was less than 0.2. Validation tests showed that the response surface methodology is an effective method for optimizing the flocculation mechanism.

Effects of polyelectrolytes on reduction of model compounds via coagulation

Dual-chemical retention systems based on 2 cationic polyacrylamides, a colloidal silica, and a globular anionic polymer microparticles were investigated and an exfoliated nanoparticle indigenous mica mineral, sericite, was examined for its efficacy in substituting commercial microparticle preparations. The results indicated that nanosericite generated FPR between 76.9 and 80.9% for fines and chemicals. Its ash retention values, however, were higher and tended to increase with doses of polymer, nanosericite, or Sc to between 16 and 24%. As for paper physical properties, nanosericite was not amenable to substitute the c-PAMb/polymer with only handsheet stiffness superior to the combination. Nanosericite, however, showed good substitution capacity than the c-PAMa-colloidal silica combination. Regardless of the c-PAMa doses, all examined handsheet physical properties incorporating nanosericite were superior to colloidal silica. The optimal performance was observed with c-PAMa dose of 200 ppm. Optical properties of the handsheets indicated that with nanosericite substitution, brightness values were comparable to the polymer group, while its substitution capacity for colloidal silica decreased with increasing c-PAMb dose. Only at c-PAMa dose of 300 ppm, it appeared to have good substitution for colloidal silica. Substituting nanosericite for colloidal silica appeared to reduce the c-PAMa charge and increased the overall cost effectiveness.