Basic Studies on the Dual-Polymer Flocculation of Iron Hydroxide

The efficiency of synthetic flocculants in flocculation processes has been identified by several authors over the years, and this makes it applicable in the industry. Nowadays, studies are focused on the combination of polymers for optimal performance. In this study, the physicochemical conditioning of iron hydroxide suspension (obtained sludge from the lignite mined sites in the Lusatia region of Germany) was investigated with flocculants of different properties as single polymer conditioning (C492 and A130) and as dual-polymer conditioning (C492+N300, A130+N300 and C492+A130) using Jar test. C492 is a cationic flocculant, A130 is an anionic flocculant, and N300 is a non-ionic flocculant. Turbidity of the supernatant and the sludge volume index were the assessing parameters considered under dosage range of 0.4, 0.8, 1.2, 2.0, 2.8 and 3.6 mg/gTS. The obtained optimization results were compared to the actual separation with respect to specific filtration resistance from pressure filtration. The obtained results show some interesting differences which are discussed in this book.

Text Sample:
Chapter 3.2 Method:
3.2.1 Charge Quantification:
Due to the form of flocculants that was used (solid form), stock solution (1.0 g/l) was prepared in order to save the preparation time and conserve the flocculants. This was later diluted to appropriate concentration. Each of the solutions was used within a period of 5 days for effectiveness and accuracy of result. For the quantification of each flocculants, 10ml of the sample was poured into the measuring cell of the PCD03, the piston ring was appropriately positioned inside the measuring cell which was fixed to the PCD meter. The motor was switched on and allowed to run for about 1-2 minutes for the stabilization of the potential. The burette tip of the automatic titrator was inserted for the titration. Poly-DADMAC polyelectrolyte was used for A130 and N300 while Pes-Na was used for C492. Ferric hydroxide was quantified using Poly-DADMAC polyelectrolyte.
3.2.1.1 Operating Principle of PCD03:
The Charge Particle Detector meter works according to the principle of streaming current detection. There was a gap which was defined between the piston and the wall of the vessel (measuring cell). The piston moves through a motor that drives it up and down instituting a fluid flow whereby free counter ions are swept away and separated from the adsorbed sample in the cell. A current is then induced by the counter ions in the built-in gold electrode which displays the streaming potential (Figure 6). [...].
For quantitative charge measurement, polyelectrolyte or colloid, titration was conducted with the Particle Charge Detector (PCD) which uses the streaming current to identify the point of zero charge 0 mV (equivalence point). An oppositely charged polyelectrolyte was used with an already known charge density and added to the sample as titrant. The titrant charges then neutralize the existing charge of the sample to the isoelectric equivalence point which was the termination point for the titration. The common polyelectrolyte used include Pes Na 0.001N (Anionic polyelectrolyte) and poly-DADMAC 0.001N (cationic polyelectrolyte). The specific charge quantity q (eq/g) can be evaluated using equation 3. [...].
Where V is the consumed titrant volume (ml), C is the titrant concentration (eq/l) and wt is the solids of the sample or its active substance (g).
3.2.2 Flocculation Tests (Jar Test):
The experimental set up is shown in Figure 7. The five beakers (representing each of the dosage range) were filled with 250ml of the Ferric Hydroxide and was placed under each paddle of the flocculator ensuring free movement to enhance proper mixing and prevent breaking of the glass. The fast mix was at 200 rpm which lasted for 1 minute while the slow mix was at 30 rpm for 5 minutes. The fast mix helps to properly mix the suspension with the polymer while the slow mix is meant for the aggregation of flocs. Careful attention needs to be given to the mixing velocity especially the 'slow mix' because the optimum size of the larger flocs formed during the slow mix cannot be reserved again when torn. [...].
The dosage range considered includes; 0.4, 0.8, 1.2, 2.0, 2.8, and 3.6 mg/gTS. The physicochemical treatment of the ferric hydroxide was performed for single polymer conditioning using C492 (cationic flocculants) and A130 (Anionic flocculants) individually. The dual-polymer conditioning was performed with a combination of non-ionic flocculants N300 with each of the flocculants used as single polymer (C492+N300 and A130+N300) at a ratio of 1:3 while the two main flocculants were as well combined together (C492+A130) at a ratio of 1:1.
The evaluating parameters; turbidity of the supernatant and sediment height was taken and recorded after 30 minutes for each of the experiment. The supernatant was taken at an average height of 3cm for the turbidity measurement. Based on the sediment height, the sludge volume index (SVI) was calculated using the formula in equation 4 below. [...].
Vs is th