A study of removal of Pb heavy metal ions from aqueous solution using lignite and a new cheap adsorbent (lignite washing plant tailings)

The present study determines the efficiency with which lignite and lignite washing plant tailings can adsorb Pb heavy metal ions. In the first experiment, the effect of size distribution on the absorbance capacity was investigated for the samples. Therefore, lignite sample was ground to five sizes (d80 = 0.600, 0.355, 0.250, 0.106 and 0.063 mm) under nitrogen (N2), and the tailings sample was classified into seven fractions, along with the original state (original state: d60 = 0.063, −1 + 0.600, −0.600 + 0.355, −0.355 + 0.250, −0.250 + 0.106, −0.106 + 0.063 and −0.063 mm). The test results showed that the optimum size distributions for lignite and tailings were d80 = 0.063 mm and the original state (d60 = 0.063 mm), respectively. Simultaneously, the adsorption capacity results of the two optimum sizes were compared with each other, and the tailings sample (d60 = 0.063 mm) gave the best results, with 9.30 mg/g Pb ions adsorbed value. Therefore, in the second study, a series of laboratory experiments using 23 full factorial designs was conducted to determine the optimum pH, contact time and initial metal concentration using the original tailings sample. The experimental studies showed that pH 9, a 120 min contact time and 300 ppm initial metal concentration gave the best results, namely an adsorption of 29.92 mg Pb ions/g.