# Separation of Iron Oxide from Harbor Waste Using Selective Flocculation
## 4 Conclusions  
The mineral phases in the sludge generated from processing \"harbor waste\" (sample K from the Constanta tailings plant) were examined. Chemical analyses, along with SEM-EDS and XRD, indicate that the material is mainly a mixture of iron ore, coal, and bauxite (gibbsite). The EDS analysis revealed that the dominant grains are primarily composed of carbon (up to 80% by weight) and oxygen, whereas the smaller grains mainly consist of iron and oxygen. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Classes,**} & \multirow{2}{*}{**Product**} & \multirow{2}{*}{**Fe,**} & \multicolumn{2}{c}{**SiO\({}_{2}\),**} & \multicolumn{2}{c}{**Al\({}_{2}\)O\({}_{3}\),**} & \multirow{2}{*}{**Ca,**} \\  & & & & \% & & \% & & \% & \% & \% \\ \multirow{2}{*}{**K2**} & \multirow{2}{*}{**\(\mu\)m**} & & \% & \multirow{2}{*}{**Input**} & \multicolumn{2}{c}{**Float/**} & \multirow{2}{*}{**Input**} & \multicolumn{2}{c}{**Float/**} & \multirow{2}{*}{**Input**} & \multicolumn{2}{c}{**Float/**} \\  & & & & & & & & & **Settled** & \\ \hline \multirow{2}{*}{**K1**} & \(-450\) & Float & 7.50 & \multirow{2}{*}{36.52} & 31.32 & \multirow{2}{*}{10.27} & 9.51 & \multirow{2}{*}{6.36} & 5.78 & \multirow{2}{*}{3.17} & 4.06 \\  & \(+250\) & Settled & 92.50 & & 36.26 & & 10.29 & & 6.34 & 6.34 & 3.25 \\ \multirow{2}{*}{**K2**} & \(-250+\) & Float & 11.72 & \multirow{2}{*}{34.58} & 17.42 & \multirow{2}{*}{11.04} & 4.91 & \multirow{2}{*}{6.83} & - & 1.33 \\  & \(25\) & Settled & 88.28 & & 36.01 & & 10.53 & & 5.97 & 3.05 \\ \multirow{2}{*}{**K3**} & \(-25+0\) & Float & 11.71 & \multirow{2}{*}{41.38} & 33.84 & \multirow{2}{*}{11.58} & 9.33 & \multirow{2}{*}{8.51} & 5.22 & \multirow{2}{*}{3.38} & 2.88 \\  & \(-25+0\) & Settled & 88.29 & & 38.05 & & 10.37 & & 6.29 & 3.38 & 3.42 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Weight distribution and content grade of basic chemical composition between the settling and floating parts of K1, K2, and K3 samples depending on particle size classes. XRD confirmed the presence of quartz, hematite, magnetite, calcite, dolomite, goethite, and layered silicates--phases typically associated with coal--while sulphur-containing phases (e.g., sulfides) were not detected. Additionally, studies were carried out to assess the feasibility of using selective flocculation to separate iron minerals from other impurities, employing a commercial flocculant based on anionic polyacrylamide. The findings indicate that improved selectivity of the settled material is achievable at pH 10.5 and when the deposition time is extended from one to five minutes. An increase in iron ore content after flocculation by comparison to the initial sample (34.18%) can be seen, especially in the case of the \(-25+0\)\(\upmu\)m class (41.38%), depending on the particle size class, as presented in Table 7.  
Considering the results obtained and the numerous factors influencing the selective flocculation process, further investigation is essential to optimize outcomes in such complex systems. Future research will explore extending the settling time, testing alternative flocculants and dispersants, and varying their concentrations and dosages. These preliminary tests have undoubtedly marked the beginning of a new phase in the study of selective flocculation for \"harbor waste\" (sample K). This advancement is expected to enhance the recovery of iron ore and consequently reduce waste sludge deposition, thereby contributing to the protection of both the living and working environment. Conceptualization, A.-F.M. and L.T. ; methodology, L.T., A.-F.M. and M.L. ; validation, A.-F.M., L.T. and S.S.; formal analysis, A.Z. ; resources, C.T. and E.T. ; data curation A.-F.M. and L.T. ; writing--original draft preparation, L.T. ; writing--review and editing, A.-F.M. and L.T. ; supervision, A.-F.M., L.T., M.L., A.Z. and S.S. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable.