Free Acids and Chemicals Recovery From Stainless Steel Pickling Baths

A review on methods of regeneration of spent pickling solutions from steel processing

“…This method is limited by the growing need for landfills to store the precipitate. Moreover, no selective recovery of chemicals from the mixture of Fe and Zn hydroxides and neutral salts is possible [5,9,32,38,39]. Additional problem is very high-chloride content that prohibits further use of the waste.…”

“…ED is applied for regeneration of wastestreams (mainly HNO 3 /HF from stainless steel pickling) neutralized with base (e.g., KOH) to split the stream into acid and base. The acid recovered, resulting from ED or ME, is recycled to the pickling bath and the base to the precipitation step [9]. The water after ED is reused as rinsing water.…”

“…The membrane techniques proposed to recover HCl and mixtures of HNO 3 /HF, H 2 SO 4 /HCl or H 2 SO 4 /HNO 3 and HNO 3 /HF include diffusion dialysis (DD) [9][10][11][12] and membrane distillation (MD) [13][14][15][16][17][18][19], electrodialysis (ED) with bipolar membranes [9,20,21], cation-exchange membranes [21,22], Neosepta membranes [23], and anion-exchange membranes [24] or membrane electrolysis (ME) [9,[25][26][27]. Advantages and disadvantages of the membrane techniques used for SPS regeneration are collected in Table 2.…”

“…Electrodialysis of SPS is an effective way of acid recovery and wastewater purification [9,[20][21][22][23][24][25]. This method enables not only separation of acid but also its concentration high enough to recycle the acid to be used in the pickling bath.…”

An overview of the recovery of acid from spent acidic solutions from steel and electroplating industries

“…Waste minimisation and reutilization lead to the consideration of a series of alternatives that range from separation of dissolved metallic ions (at least until levels that permits reutilization of the acid) to recovery of the acid itself in its pure states [10][11][12][13][14]. The concentration of pickling bath may be maintained by several ways:…”