Polyaluminium Chloride PAC for paper water treatment

Polyaluminium Chloride (PAC) has become the coagulant of choice for textile and paper-mill effluent treatment because it delivers rapid, cost-effective clarification while meeting increasingly stringent discharge limits. Textile wastewater is notorious for high color, COD, surfactants and variable pH; paper-mill effluent carries fibers, fillers, starch and lignin derivatives. In both matrices, PAC’s pre-neutralised, high-basicity aluminium polymer chains immediately neutralise negative colloids, bridging micro-flocs into dense agglomerates that settle in minutes rather than the hours required by alum or iron salts. The result is >95 % colour removal, 70–90 % COD reduction and up to 99 % TSS elimination from textile dye-baths, sizing streams and paper whitewater loops.

 

 

PAC’s superior performance is rooted in its chemistry. Unlike conventional alum, PAC is supplied as a stable liquid with an Al₂O₃ content of 10–18 % (or as a low-dust powder of 28–30 %). Its basicity (45–70 %) means far less alkalinity is consumed during coagulation, so textile caustic or paper-mill alkaline sizing losses are minimised. The buffered pH profile keeps the system between 6.5 and 8.5, protecting sensitive fibres and dyes from acid shock while reducing the need for post-neutralisation chemicals. In closed-loop paper machines, PAC removes anionic trash that would otherwise foul wet-end additives, improving retention and paper strength.

 

Dosage is typically 50–300 g t⁻¹ for textile effluent and 5–50 g t⁻¹ for paper-mill process water, depending on influent quality and the presence of high-molecular-weight flocculants. Sludge volume is 20–40 % lower than with alum, cutting dewatering and disposal costs. PAC is also compatible with membrane pre-treatment, extending ultrafiltration and reverse-osmosis run times in zero-liquid-discharge textile plants.

 

Environmental and regulatory benefits are equally compelling. PAC contains no mercury, lead or chromium; its low residual aluminium (<0.1 mg L⁻¹) complies with EU, EPA and ISO standards for recycled water reuse. By enabling water recycling and colour removal, PAC helps textile and paper producers meet ZDHC, Oeko-Tex and REACH commitments while reducing freshwater intake by up to 60 %. In short, Polyaluminium Chloride PAC offers a single, robust solution that clarifies complex textile and paper effluents, safeguards downstream processes and supports sustainable manufacturing.