СОРБЦІЯ ІОНІВ МІДІ (ІІ) З ВОДИ ФОСФОРИЛЬОВАНОЮ СОСНОВОЮ ТИРСОЮ

Abstract

Wastewater containing heavy metal ions in low concentrations pose a problem because there are difficult for treatment. Ion exchange purification of water is inefficient and uneconomical because of the presence of other dissolved salts, particularly hardness ions. Sorption extraction of metals from wastewater received fairly widespread due to the high efficiency and no secondary pollution. Using sawdust for sorption of heavy metal ions from wastewater are the subject of many studies. This natural material is formed in large quantities as waste and has a low cost. Wood sawdust is able to be used as sorbent due to the presence of lignin in its composition. Due to the presence of phenolic, carboxyl and hydroxyl functional groups in the composition of sawdust, heavy metal cations are bound. The limiting factor in the use of sawdust for cleaning the wash water is its low absorption properties. The aim of the research was to obtain a sorption material based on sawdust with improved sorption properties by treating them with ammonium salts. The paper is devoted to the synthesis and investigation of sorption properties of materials, obtained by treatment of pine sawdust by ammonia solutions, ammonium salts of hydrochloric, sulfuric and phosphoric acids (also in presence of carbamide) at room temperature and heat-treated after impregnation. It is found that ammonia did not have a significant impact on the sorption properties of the sawdust, in contrast to (NH 4 ) 2 SO 4 and (NH 4 ) 3 PO 4 . The lower residual concentrations of Cu 2+ were achieved if sawdust soaking was followed by heating. Depending on the concentration of ammonium phosphate and sulfate, obtained sawdust contained black particles or was completely black, probably due to wood charring because drying of soaked sawdust was accompanied by thermal decomposition of ammonium salts leading to formation of acidic salts (hydrosulphates, hydrophosphate, dihydrophosphate) and phosphoric acid that had dehydrating properties. The ammonium salts, when heated to 160 °C, were partially or completely decomposed to phosphoric acid and acidic salts, sawdust which impart ion exchange properties to sawdust. During sorption of Cu 2+ from CuSO 4 solution with increasing concentration of and (NH 4 ) 3 PO 4 , taken for modifications, specific sorbtion capacity also increased from 1.3 to 2.4 mg/g, while pH decreased from initial 4.94 to the values 3.36–2.86. Lowering the pH was greater the higher the concentration of modifier. At low concentrations of modifier, due to ion exchange, about half the copper was removed and this proportion increases to 92 % with the increase of concentrations of ammonium phosphate in modifying solution. Another possible mechanism for copper fixing from solution is a complex formation of phosphorus-containing functional groups, which are embedded in lignin during phosphorylation. Carrying out the sorption of Сu 2+ by sawdust, treated and (NH 4 ) 3 PO 4 under the same conditions, but maintaining costant pH in the range of 4.5–5, specific sorption has almost doubled and, from a certain concentration of modi-fier – 9 %, little changed with growth the concentration of the latter. Therefore, in the next series of experiments with a mixture of sawdust was modified by and (NH 4 ) 3 PO 4 with the same concentration and 5 %-urea, and tested its absorption properties without maintaining the pH and maintaining it at 4,5–5 during sorption. In similar final pH values, the application of pine sawdust, phosphorylated in the presence of urea, allowed to achieve significantly lower residual concentrations