Influence and Countermeasures of Plating Chemicals on Zinc Wastewater Treatment

Abstract

To comply with zinc effluent regulations, we investigated the influence of plating chemicals on zinc removal from zinc chloride solutions by coagulation with sodium hydroxide. Plating chemicals including ethylenediaminetetraacetic acid disodium salt (EDTA･2Na) , ammonium chloride, sodium citrate, triethanolamine (TEA) , sodium diphosphate, and potassium dihydrogen phosphate decrease zinc removal capabilities. The zinc removal capability in the solutions depends on the concentrations of additive compounds. Especially, the addition of EDTA･2Na and sodium diphosphate exert an important influence that is attributable to the complex forming reaction of zinc and EDTA･2Na. For the addition of 8.8 mg/L EDTA･2Na, removal of zinc from the solutions and exceeding the effluent regulation value of zinc was difficult. Furthermore, to reduce compounds interfering in wastewater, we examine emissions management. Results demonstrated that the drain of barrel processing increases the interfering compounds in wastewater. Plating chemicals disturb the zinc wastewater treatment.

Pretreatment with fine bubbles for effective zinc ion precipitation and removal from zinc electroplating wastewater

“…Surfactants can also effectively improve the cleaning effect by decreasing the surface tension of FB water, which increases the retention and penetration effect of FBs. [ 29 ] However, complexing agents present in surfactants can inhibit metal flocculation when mixed with plating wastewater [ 5 ] ; hence, care must be taken when using them in the plating process.…”

“…When degreasing agents are mixed in, the complexing agents (such as ethylenediamine‐ N , N , N ', N '‐tetraacetic acid) present in the degreasing agents form water‐soluble complexes with zinc, which deteriorates treatability. [ 5 ] However, no complex formation reaction occurred with FB wastewater and excellent treatability was achieved. In addition, FBs have a flotation effect, which may deteriorate treatability owing to the diffusion of zinc hydroxide flocs, thereby leading to floc destruction.…”

“…Therefore, the measures for zinc wastewater treatment should comply with the standard value of zinc in the wastewater stipulated by the regulation. [ 5 ]…”

“…Therefore, the measures for zinc wastewater treatment should comply with the standard value of zinc in the wastewater stipulated by the regulation. [5] One of the reasons for the difficulty in treating plating wastewater is the wide variety of chemicals present in the wastewater. In metal surface treatments such as plating, the condition of the metal surface before treatment significantly affects product quality.…”

“…[9][10][11] However, precipitation is inhibited by the presence of complexing agents such as degreasing agents in the cleaning process, which react with heavy metals to form water-soluble complexes. [5] The removal of these complexing agents is necessary to ensure proper wastewater treatment [12] ; however, owing to the wide range of complexing agents present in degreasing products, this removal is difficult. Therefore, it is important to develop a cleaning technology that does not use degreasing agents which inhibit wastewater treatment.…”