PAC vs Ferric Chloride | Phosphate, Colour, Sludge | ETP

PAC (poly aluminium chloride) is a pre-hydrolysed aluminium polymer, typically written [Al₂(OH)ₙCl₆₋ₙ]ₙ. Industrial powder from Drashti is usually 28–30% Al₂O₃ (CAS 1327-41-9, HSN 28273200). It is dosed for turbidity, TSS and many colour loads with relatively dense sludge.

Ferric chloride is FeCl₃ (CAS 7705-08-0). Commercial supply is usually industrial liquid (often quoted around 40% as product — confirm assay on COA) or powder. Anhydrous and hexahydrate are different commercial forms; do not treat them as interchangeable with liquid without matching your last COA. Drashti is a Vadodara supplier/stockist of industrial liquid and powder grades — not a primary manufacturer.

Phosphate: ferric precipitates orthophosphate as iron phosphate. If your GPCB/CPCB consent lists total phosphorus, ferric (or a ferric-assisted program) is usually the first trial — PAC is weaker on P.

Colour and sulfide: reactive-dye and some chemical streams respond to iron hydrolysis and oxidation of sulfides. PAC may still be the daily coagulant; ferric is the colour/P spike chemical. PCB and etching shops buy ferric for process chemistry, not for municipal-style clarification — share the application on the RFQ so grade and impurity notes match.

Sludge and dewatering: PAC flocs are typically denser than alum and often easier on belt presses than high-ferric programs. If landfill or centrifuge hours are your real cost, PAC is the default.

Chloride TDS and corrosion: every kg of ferric chloride adds chloride. Plants already near TDS or chloride limits, or running carbon-steel dosing lines without lining, usually stay on PAC for the base load. Residual iron colour after chlorination is another reason to keep ferric off potable or reuse trains.

Do not dump both into the same flash-mix tank without a jar test. Typical patterns: PAC as primary coagulant, ferric as a second point for colour/P; or ferric at primary clarifier and PAC at tertiary polishing. Dose points, pH and polymer addition order all change the result.

Festival or campaign production in Gujarat dye houses often needs a seasonal ferric boost. That is an operations choice, not a reason to replace PAC stock. Keep both SKUs on one supplier account so packing and COA stay consistent.

For PAC: powder vs liquid, Al₂O₃ %, pack (25/50 kg or jumbo). For ferric: liquid % vs powder; if you need anhydrous or hexahydrate, write that explicitly and attach the last COA — we will not substitute forms. Add flow, current dose, phosphate/colour targets, and whether dosing equipment is HDPE/FRP or steel.

Drashti stocks PAC powder and ferric chloride from Vadsar with batch COA and MSDS. No public list prices. GST 24AGLPC6288M1ZX.