## 3 Results and Discussion
### Comparison of the Efficiency of IME* and Sorption Processes with a Use of GAC Soaked in LL  
The results of the experiments with the use of GAC 4H subjected to preliminary saturation before the IME process in the LL are as follows: raw (pH 7.8) and LL after PC at pH 3 are presented for pr. 1.4 in Table 5. The results obtained in the c-IME* and m-IME* processes (Fe/GAC 40/10 g/L) were compared with the results for the IME process and sorption on GAC without pre-saturation for the same LL sample.  
The presented results show that, after 24 h of soaking in LL, the GAC still could adsorb some impurities from the new portion of LL--after transferring the preliminarily soaked in LL GAC to the new batch of LL and after 60 min of an additional sorption process, an additional value of COD removal was obtained. The value of the additional COD removal depended on the type of LL in which the GAC was preliminarily soaked and the type of LL in which the additional sorption was carried out.  
The total COD removal in the \"sorption\" (there is sorption together with the precipitation of HS from acidic solution) process from raw LL, acidified to pH 3 (without PC), with the use of GAC soaking in raw leachates at pH 7.8, was 21.9%. Similarly, the \"sorption\" from the raw LL with the use of the GAC after soaking in LL after PC in pH 3 was 18.1%.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Sample 1.4** & **Raw LL** & **PC pH 3** & **m-IME 120 min** & **m-IME 120 min** \\  & & & **120 min** & **/H2O2 60 min** \\ \hline COD [mg O2/L] & 1092 & 955 & 402 & 170 \\ \hline \(\Delta\)COD [\%] & & 12.5 & 44.6 & 82.1 \\ pH & 8.2 & 3.0 & 6.2 & 9.0 \\ Conductivity [mS/cm] & 8.19 & 9.71 & 8.96 & 9.81 \\ Ntotal [g/L] & 343 & 336 & 242 & 198 \\ TOC [mg/L] & 381 & 326 & 130 & 88 \\ BOD5 [mg O2/L] & 131 & - & 129 & 78 \\ BOD5/COD & 0.12 & - & 0.32 & 0.39 \\ \hline Absorbance 254 [nm] & 11.82 & 8.96 & 0.562 & 0.103 \\ SUVA [m2/gC] & 0.0309 & 0.0275 & 0.0042 & 0.0011 \\ \hline \end{tabular}
\end{table}
Table 4: LL characteristics after subsequent purification stages, sample 1.3.  
Figure 8: Efficiency of LL treatment, from the left: raw leachate, after PC, after m-IME and after m-IME/H2O2 (sample 1.3).  
The presented results show that some additional sorption on the GAC occurred--the COD removal is higher than those caused only by PC (16.2%), especially in case of the GAC soaking in raw LL.  
In the case of the LL after PC, the additional sorption process investigated on the GAC soaked in raw LL was the most significant--18.7%. It is worth noticing that the total COD removal in the c-IME process conducted with a use of that type of GAC was 38.1%; thus, the additional sorption (which was assumed by most authors as not occurring in LL after soaking in LL) has a big share in the COD removal. On the contrary, additional sorption on the GAC soaking in LL after PC and from the LL also after PC in pH 3 was insignificantly low--1.1% (the total COD removal in the m-IME process with a use of that GAC was 40.9%).  
The presented results clearly show that the assumption that is made by some authors that after soaking GAC in LL the sorption is eliminated from the IME process is wrong. That phenomenon could be explained based on the nature of the sorption process--the soaking of GAC in LL led to establishing some sorption balance and some saturation of GAC, but, after transferring GAC to the new portion of LL, a new sorption balance must be established and additional sorption on GAC occurs. The only way of almost total elimination of sorption from IME process is conducted the process in LL after PC and with a use of GAC after soaking in LL also after PC.