A novel electrochemical process for the recovery and recycling of ferric chloride from precipitation sludge

Abstract

During wastewater treatment and drinking water production, significant amounts of ferric sludge (comprising ferric oxy-hydroxides and FePO 4 ) are generated that require disposal. This practice has a major impact on the overall treatment cost as a result of both chemical addition and the disposal of the generated chemical sludge.Iron sulfide (FeS) precipitation via sulfide addition to ferric phosphate (FePO 4 ) sludge has been proven as an effective process for phosphate recovery. In turn, iron and sulfide could potentially be recovered from the FeS sludge, and recycled back to the process. In this work, a novel process was investigated at lab scale for the recovery of soluble iron and sulfide from FeS sludge. Soluble iron is regenerated electrochemically at a graphite anode, while sulfide is recovered at the cathode of the same electrochemical cell. Up to 60±18% soluble Fe and 46±11% sulfide were recovered on graphite granules for up-stream reuse. Peak current densities of 9.5 ± 4.2 A m -2 and minimum power requirements of 2.4 ± 0.5 kWh kg Fe -1 were reached with real full strength FeS suspensions. Multiple consecutive runs of the electrochemical process were performed, leading to the successful demonstration of an integrated process, comprising FeS formation/separation and ferric/sulfide electrochemical regeneration.

Highly Porous Hypercrosslinked Polymers Derived from Biobased Molecules

“…FeCl 3 is al ow-cost Lewis acid extensively used in water treatment processes but could arguably have sustainability issues when it comes to mining and the use of chlorine. [25] FeCl 3 can potentially be recycled, as indicated by studies on sludge from water treatment [26] and spent AlCl 3 alkylation sludge. Today roughlyh alf of all Cl 2 is produced by membrane cells.…”

“…[24] Scrap iron is already used as as ource of iron. [25] FeCl 3 can potentially be recycled, as indicated by studies on sludge from water treatment [26] and spent AlCl 3 alkylation sludge. [27] Sulfolane is compatible with Lewis acid catalyzed alkylation,i nexpensive, solvates aromaticsw ell, hasahigh boiling point, and has been recommended as ac omparatively sustainable solvent.…”

Implementation of a Sulfide–Air Fuel Cell Coupled to a Sulfate-Reducing Biocathode for Elemental Sulfur Recovery

“…Graphite granules with a diameter of 6 mm or higher (El Carb 100; Graphite Sales, Nova, OH, USA) were used as cathode material, which was placed in the second frame. The third frame contained the fuel cell (FC) that consisted of an anode made of reticulated vitreous carbon (RVC) of 19 × 4 × 1 cm 3 (45 ppi pore size, Duocel RVC foam; ERG, USA–chosen because it can facilitate spontaneous HS − oxidation without significant S 0 deposition/fouling [ 34 ]), a plastic mesh separator to avoid short-circuiting between the two electrodes of the FC and a passive gas diffusion air-cathode. The latter consisted of a carbon cloth coated with carbon powder and platinum suspension on the inner side (0.125 mg cm −2 , platinum nominally 40% on high surface area advanced carbon support HiSPEC 4100 TM powder; Alfa Aesar, Heysham, UK), whereas the outer side was coated with a polytetrafluoroethylene (PTFE 60% w / w dispersion in H 2 O; Sigma-Aldrich, St. Luis, MO, USA) solution (4 layers), which permitted oxygen diffusion into the cell while preventing electrolyte permeation [ 35 , 36 ].…”

Applications of Electrokinetic Remediation inEnvironmental Restoration

“…Iron has been used in wastewater treatment industry around the globe for removal of phosphorous. The addition of iron to wastewater results in the formation of a sludge rich in a ferric phosphate [6,7]. The current practice is to dispose of the sludge containing high concentration of ferric phosphate which has an economical value.…”

“…In the last few decades, the increase in the demand for drinking water, due to the increase in the world population, has resulted in requirement for improvement in desalination to overcome water scarcity around the globe [5]. On the other hand, the growth in the wastewater treatment industry has resulted in sludge containing high concentration of ferric phosphate [6]. The scientist and researchers are constantly looking for new ways to improve the current practices.…”