[6] [6] PATHAK A, ROY A, MANNA M. Recovery of zinc from industrial waste pickling liquor[J]. Hydrometallurgy, 2016, 163: 161-166.

[7] [7] DEVI A, SINGHAL A, GUPTA R,et al. A study on treatment methods of spent pickling liquor generated by the pickling process of steel[J]. Clean Technologies and Environmental Policy, 2014, 16: 1515-1527.

[9] [9] DABSHBASHY T, SACMACI S, LGEN A,et al. A solid phase extraction procedure for the determination of Cd (Ⅱ) and Pb (Ⅱ) ions in food and water samples by flame atomic absorption spectrometry[J]. Food Chemistry, 2015, 17: 591-596.

[13] [13] LEE D H, HAN S C, KIM T H,et al. Highly sensitive analysis of boron and lithium in aqueous solution using dual-pulse laser-induced breakdown spectroscopy[J]. Analytical Chemistry, 2011, 83(24): 9456-9461.

[14] [14] LAZIC V, FANTONI R, PALUCCI A,et al. Sample preparation for repeated measurements on a single liquid droplet using laser-induced breakdown spectroscopy[J]. Applied Spectroscopy, 2017, 71(4): 670-677.

[15] [15] WALL M, SUN Z, ALWAHABI Z T. Quantitative detection of metallic traces in water-based liquids by microwave-assisted laser-induced breakdown spectroscopy[J]. Optics Express, 2016, 24(2): 1507-1517.

[19] [19] MA S, TANG Y, MA Y,et al. The pH effect on the detection of heavy metals in wastewater by laser-induced breakdown spectroscopy coupled with a phase transformation method[J]. Journal of Analytical Atomic Spectrometry, 2020, 35(1): 198-203.