## 3 Results and Discussion
### Leaching Tests  
#### 3.2.1. _Mobilization and Availability of Metals_  
Only a part of the total content of the elements present in the geopolymeric matrices is available to be leached, and it depends on the phases of the matrix so the concentration on the solution may be significantly lower than the total content [29].  
All the analyzed elements As, Ba, Cr, Cu, Mo, Ni, Pb, Sb, Se, Zn, and Cd except for Hg, present a concentration higher than the quantification limit for both, availability and compliance leaching test (Figure 3). Some of these elements such as Zn, Cd, Cu, Cr, and Pb, coming mainly from the EAFD, are retained in the geopolymeric matrix by means of a chemical immobilization in combination with a physical mechanism of microencapsulation [16]. For others such as As, Mo, and Se, there is evidence that chemical immobilization is weak, so unless physical microencapsulation is strong and durable over time geopolymerization is not a suitable treatment for these elements [13].  
The elements, which present the greater availability, are Zn--followed by Pb, Ba, Cu, and Ni--and to a lesser extent As and Cd. In general terms, it can be said that the availability of the elements decreases with increasing the curing temperature, since, as it had seen, more densified structures were achieved. There are elements whose availability is not influenced by the amount of EAFD introduced into the material, as Ba or Ni and even, in the case of As, it decreases when increasing the dosage of waste. This fact suggests that the arsenic leaching comes from the clay [23].  
The results of the equilibrium test show that curing temperature affects mobility more than availability. Up to 10% EAFD dosages the leaching behavior with temperature is  
Figure 2: Microstructure of the geopolymer matrices with different dosages of EAFD and curing temperatures.  
similar, while at higher dosages a difference is observed in the trend, being lower in all cases, the higher the curing temperature.  
The leachates from the equilibrium tests have alkaline pH, due to the release of free alkali from the geopolymers when immersed in deionized water. The pH remains constant regardless of the dosage of the EAFD and the curing temperature of the geopolymers, between the values 11.75 and 11.99. Due to these high pH values, most of the oxyanionic elements (as As or Se) leach more in the geopolymeric matrix than in the raw materials. This means that for both elements, the concentration in the leachate exceeds the limit of the regulations for non-hazardous landfill [26]. Although the leaching of As is a fact that is described in several environmental studies of day ash or clay based geopolymers [23; 49; 50; 51; 52], authors who introduce EAFD for their immobilization, do not monitor this element, only those associated with the steel dust (Zn, Pb, Cr, Cd) [16; 17; 37]. This also occurs with other authors who use geopolymers to immobilize another hazardous waste, [34; 39; 53; 54] none of which studies the behavior of arsenic.  
To promote the immobilization of As, [PERSON] and [PERSON] [51] propose the use of mixed systems together with blast furnace slag, rich in Ca, to help its immobilization.