Removal of Cu (II) from Industrial Wastewater Using Mechanically Activated Serpentinite

: We investigate with this study the e ﬀ ectiveness of mechanically activated serpentinite in capturing Cu (II) from the multi-constituent acidic wastewater of the pit lakes of the Agios Philippos mine (Greece), proposing speciﬁc areas with serpentinites suitable for such environmental applications. For this purpose ultramaﬁc rock samples that are characterized by variable degrees of serpentinization from ophiolitic outcrops exposed in the regions of Veria-Naousa and Edessa have been examined regarding their capacity to remove the toxic load of Cu (II) from wastewater after having been mechanically activated through a Los Angeles (LA) machine (500, 1000 and 1500 revolutions). The more serpentinized and mechanically activated samples, as they have been characterized after a combination of various mineralogical, petrographic, geochemical analyses as well as after di ﬀ erent stresses of abrasion and attrition, seem to be more e ﬀ ective in Cu removal than the less serpentinized ones. Selective removal of Cu (II) in the wroewolfeite phase was obtained by using the mechanically activated highly serpentinized ultramaﬁc rocks. Furthermore, areas with highly serpentinized ultramaﬁc rocks deﬁned after petrographic mapping, using GIS method, which can potentially be used as ﬁlters for the e ﬀ ective Cu (II) removal from industrial wastewater are suggested.


Introduction
Today, societies are vastly affected by negative changes in the quality of water, air, and soil as a result of human activities. More specifically, large volumes of wastewater present within lakes, river or in industries, put intense pressure on mankind. Among the different types of pollutants, non-organic ones have a high-risk factor and are characterized as being harmful [1]. Mitigation of toxicity factors identified within water considered as waste that has been produced by industrial activities is a main concern in modern-day societies. Wastewater produced from industrial and human activities, must be brought back the societies as well as to Nature, which includes rivers, lakes and land [2]. More specifically, acidic drainage or pit lakes produced by past mining activities are held as being It is widely accepted by the broad scientific community that different hydrated silicate minerals and especially clay minerals (that encompass serpentine), demonstrate abilities in the adsorption of undesirable heavy metal elements. Serpentine constitutes a group of high-Mg 1:1 layered trioctahedral minerals, with its structural formula being Mg 6 (Si 4 O 10 )(OH) 8 . It is characterized as chemically simple but from the view of texture can be present in various forms. The serpentine mineral group occurs in three polymorphs: the high pressure antigorite and the low pressure chrysotile and lizardite. Lizardite in particular displays an ideal layered topology and on the other hand chrysotile has a bent structure and antigorite is often modulated [28,29]. Serpentine polymorphs belong to the phyllosilicate mineral group that displays a 1:1 layered structure, which comprises tetrahedral and octahedral sheets [28]. Four distinct O-H chain groups were identified in serpentine minerals. These are classified into two distinct topologies based on their (OH) positioning. Three of the four O-H groups are situated on the inner surface amongst two layers, whereas the third is located within the layer. The primitive unit serpentinite cell is held responsible for the cohesive attachment of the two successive layers that form hydrogen bonds [28,30].
When serpentinite is attached through the application of mechanical force activation (e.g., ball impact), this results in structural changes that mostly affect the OH groups that could potentially be brought to a looser state in the octahedral positions, enhancing the dispersal of the latter by the effects of water. When the serpentine structure is damaged through grinding, it becomes incapable of maintaining atom arrangements in a proper order to preserve its crystallinity. Scientists like Huang [31] have used activated serpentine in order to remove Cu from wastewater. The raw serpentine without grinding operation adsorbs less Cu than the chemo-mechanically-activated serpentine.
The aim of this study is the selective capture of Cu (II) within the crystalline structure of serpentine from tmechanically activated serpentinized ultramafic rocks from the acidic wastewater of a pit lake of the Agios Philippos mine (Greece). The suggestion of specific areas in Greece that present serpentinized ultramafic rocks suitable for Cu capture is a supplementary goal of this study.

Geological Description of Rock Materials Sources
Representative serpentinized rocks deriving from the Veria-Naousa and Edessa ophiolite complex (Greece) have been selected for studying their effectiveness in the removal of Cu from industrial wastewater after having been mechanically activated. The Veria-Naousa ophiolite belongs to the Almopias subzone (Axios geotectonic zone) in northern Greece. Its sequence consists of intense and highly tectonized serpentinized lherzolite and harzburgite of 46.76 km 2 total surface area (calculated via ArcMap 10.1), penetrated by scarce pyroxenitic dykes [32], and from gabbro, diabase and pillow basalt ( Figure 1).
Remnants of oceanic lithosphere (Upper Jurassic to Late Cretaceous) constitute the Edessa ophiolite complex which was thrust out of one or more ocean basins [34][35][36]. This complex presents intense tectonization and consists of several tectonic units [37,38] such as serpentinized ultramafic rocks (lherzolite and harzburgite) of 50.34 km 2 total surface area (calculated via ArcMap 10.1). Moreover, diabase is the main mafic lithotype of the complex, whereas gabbro, basalt as well as diorite are less frequent ( Figure 2). Remnants of oceanic lithosphere (Upper Jurassic to Late Cretaceous) constitute the Edessa ophiolite complex which was thrust out of one or more ocean basins [34][35][36]. This complex presents intense tectonization and consists of several tectonic units [37,38] such as serpentinized ultramafic rocks (lherzolite and harzburgite) of 50.34 km 2 total surface area (calculated via ArcMap 10.1). Moreover, diabase is the main mafic lithotype of the complex, whereas gabbro, basalt as well as diorite are less frequent ( Figure 2).    [39] after fieldwork and mapping using ArcMap 10.1; the area of investigation is shown in the black rectangle; the green color shows the serpentinized ultramafic rocks of the region.

Materials and Methods
Taking into account how effective the serpentinite was in removing Cu from the wastewater from the pit lake from the Agios Phillippos Kirkis mine [26], four serpentinites, derived from the aforementioned ophiolite complexes and presenting different degree of serpentinization were used after their mechanical activation to various degrees to examine the mechanism through which serpentinite can become more effective in the removal of Cu.

Characterization of the Studied Rock Materials
The first stage for the characterization of the investigated rocks is their petrographic examination (mineralogical and textural features) with the aid of a Leitz polarizing optical microscope (Leica Microsystems, Wetzlar, Germany). The modal composition of the investigated serpentinites was also identified using powder X-ray diffraction (XRPD) analysis, with a Bruker D8 Advance Diffractometer (Bruker, Billerica, MA, USA), with Ni-filtered CuKα radiation. The scanning area for bulk mineralogy of the samples covered the 2θ interval 2-70 • , with a scanning angle step size of 0.015 • and a time step of 0.1 s. The modal composition was identified with the DIFFRACplus EVA 12 ® software (Bruker-AXS) based on the ICDD Powder Diffraction File of PDF-2 2006. The mineral phases were semi-quantified with the TOPAS 3.0 ® software (TOPAS MC Inc., Oakland, CA, USA), based on the Rietveld method refinement routine. The routine is based on the calculation of a single mineral-phase pattern regarding to the crystalline structure of each mineral, and the refinement of the pattern using a non-linear least squares routine. According to the study by Bish and Post [40], the quantification errors were calculated and they are estimated to be~1%. Polished thin sections of the examined rock samples were analyzed in scanning electron microscopes (SEM) in order to identify their mineralogical characteristics. Serpentine minerals microanalyses were carried out in a JEOL JSM-6300 SEM equipped with energy dispersive (EDS) using the INCA software (version). The scanning electron microscope used is located in the Laboratory of Electron Microscopy and Microanalysis (University of Patras, Greece). Operating conditions were accelerating voltage 25 kV and beam current 3.3 nA, with a 4 µm beam diameter. The total counting time was 60 s and dead-time 40%. Synthetic oxides and natural minerals were used as standards for the analyses, where the detection limits are~0.1% and accuracy better than 5% was obtained. Furthermore, an XRF (X-Ray fluorescence) spectrometer and a sequential spectrometer (ICP-ES) were used for the determination of the major and trace elements of the studied samples, which were carried out at Bureau Veritas Mineral Laboratories (Vancouver, BC, Canada).

Methodology for the Cu (II) Removal
The studied serpentinites were placed in the Los Angeles (LA) machine in order to become mechanically activated after they have been sieved in the No. 14 sieve (1.40 mm). The Los Angeles (LA) machine is a rotating drum which contains certain number of steel spheres. Los Angeles (LA) test constitutes a basic test which indicates the mechanical quality of aggregates rocks by identifying their resistance in abrasion and attrition. At this stage, serpentinite samples were rotated in the LA machine for 500, 1000 and 1500 revolutions, respectively. Then, the samples were sieved appropriately in order to reach the grain size of 0.8-0.6 mm which then used as filters in batch type columns. Serpentinites that were not mechanically activated were also used as filters in the batch type columns after having been sieved appropriately in order to reach a grain size between 0.8 and 0.6 mm.
The next stage included an experimental arrangement consisting of columns of borosilicate glass of 20 mm diameter. In each column 70 gr of the different mechanically activated serpentinites (derived from the different revolutions used in the LA machine) was used, and 300 mL of wastewater was passed through each column four times. After this four pass procedure, wastewater samples were further processed for geochemical analysis of Cu concentration, which was performed in the Institute for Solid fuels Technology and Application of the National Centre for Research and Technology Hellas using conjugated plasma argon mass spectrometry. All the sorption experiments were carried out at room temperature (25 ± 2 • C).

Petrographic Features of the Studied Rock Materials
Two types of serpentinized ultramafic rocks regarding their degree of serpentinization were collected from the studied areas. Their textural and mineralogical characteristics are analyzed below in Figure 3. Technology Hellas using conjugated plasma argon mass spectrometry. All the sorption experiments were carried out at room temperature (25 ± 2 °C).

Petrographic Features of the Studied Rock Materials
Two types of serpentinized ultramafic rocks regarding their degree of serpentinization were collected from the studied areas. Their textural and mineralogical characteristics are analyzed below in Figure 3. (1) Highly-serpentinized (Group I) The primary modal mineralogical assemblage of the highly serpentinized ultramafic rocks is intensely altered, whereas relics of orthopyroxene and Cr-spinel were observed. The subhedral to euhedral Cr-spinel are frequently crosscut by secondary veins and/or surrounded by thin rims of magnetite and ferritchromit because of the effects of ocean floor alteration processes. Serpentine is the main alteration phase which forms mesh, ribbon, bastite and hourglass textures. Moreover, less chlorite and magnetite subsequently observe, likely being the result of retrograde metamorphism during exhumation ( Figure 3). (1) Highly-serpentinized (Group I) The primary modal mineralogical assemblage of the highly serpentinized ultramafic rocks is intensely altered, whereas relics of orthopyroxene and Cr-spinel were observed. The subhedral to euhedral Cr-spinel are frequently crosscut by secondary veins and/or surrounded by thin rims of magnetite and ferritchromit because of the effects of ocean floor alteration processes. Serpentine is the main alteration phase which forms mesh, ribbon, bastite and hourglass textures. Moreover, less chlorite and magnetite subsequently observe, likely being the result of retrograde metamorphism during exhumation ( Figure 3).
(2) Medium-Serpentinized (Group II) The primary assemblage of these serpentinized ultramafic rocks comprises of orthopyroxene, olivine, less of clinopyroxene, olivine and Cr-spinel constituting less than 30% of the whole assemblage. Porphyroclasts of orthopyroxene exhibit exsolution lamellae of clinopyroxene, typical characteristic of mantle peridotites. Olivine displays porphyroclastic grains and smaller neoblasts. Locally, olivine porphyroclasts show strain lamellae, undulose extinction, shearing and recrystallization ( Figure 3). Clinopyroxene appears as relict subhedral porphyroclasts. Crystals of Cr-spinel presented as subhedral to euhedral and they display an irregular distribution of ferritchromit compositional areas. The boundary between the Cr-spinel (either unaltered or altered) and the ferritchromit is curved and lobate. The main secondary product is serpentine which predominantly displays ribbon and mesh textures, whereas others are chlorite and magnetite. The modal composition of the investigated serpentinites was further determined by XRPD analysis in Figure 4. (2) Medium-Serpentinized (Group II) The primary assemblage of these serpentinized ultramafic rocks comprises of orthopyroxene, olivine, less of clinopyroxene, olivine and Cr-spinel constituting less than 30% of the whole assemblage. Porphyroclasts of orthopyroxene exhibit exsolution lamellae of clinopyroxene, typical characteristic of mantle peridotites. Olivine displays porphyroclastic grains and smaller neoblasts. Locally, olivine porphyroclasts show strain lamellae, undulose extinction, shearing and recrystallization ( Figure 3). Clinopyroxene appears as relict subhedral porphyroclasts. Crystals of Cr-spinel presented as subhedral to euhedral and they display an irregular distribution of ferritchromit compositional areas. The boundary between the Cr-spinel (either unaltered or altered) and the ferritchromit is curved and lobate. The main secondary product is serpentine which predominantly displays ribbon and mesh textures, whereas others are chlorite and magnetite. The modal composition of the investigated serpentinites was further determined by XRPD analysis in Figure 4.

XRPD of Mineral Rock Materials
The X-ray diffraction enabled us to identify the crystalline phases of the tested ultramafic rocks where higher picks of serpentine were observed in samples BE.01 and ED.111B whereas samples BE.118 and ED.86B display lower picks of serpentine ( Figure 4). Serpentine content as well the content of other mineralogical phases of the studied rock samples were calculated via Rietveld method and are listed in the Table 1, where the sample BE.01 presents as the most serpentinized, while ED.86B presents as the less serpentinized sample. The identification of the degree of

XRPD of Mineral Rock Materials
The X-ray diffraction enabled us to identify the crystalline phases of the tested ultramafic rocks where higher picks of serpentine were observed in samples BE.01 and ED.111B whereas samples BE.118 and ED.86B display lower picks of serpentine ( Figure 4). Serpentine content as well the content of other mineralogical phases of the studied rock samples were calculated via Rietveld method and are listed in the Table 1, where the sample BE.01 presents as the most serpentinized, while ED.86B presents as the less serpentinized sample. The identification of the degree of serpentinization of the studied rock samples through the petrographic analysis via polarizing microscope is in accordance with the results of Rietveld method. Representative microanalyses of the serpentine minerals are shown in Table 2 and plotted in the diagrams of Figure   Representative microanalyses of the serpentine minerals are shown in Table 2 and plotted in the diagrams of Figure       In the diagram of Figure 5a, the analyzed serpentine minerals from Group I are mostly antigorite, while Group II are mostly lizardite and chrysotile and less antigorite. The similarity in characteristics is consistent with the plot of MgO vs. FeO (Figure 5b). FeO was calculated by the Fe 2 O 3 method in order produce the diagram shown in Figure 5b.

Geochemical Features of Rock Materials
Major and trace elements data from the studied serpentinites, along with their loss on ignition (LOI) values are listed in Table 3. LOI values vary significantly from 7.9% to 14.6% with the most serpentinized sample (BE.01) presenting the higher LOI value, while the least serpentinized one (ED.86B) presenting the lowest LOI value.

Chemical Analysis of the Wastewater
The wastewater from the selected pit lake of the Agios Philippos mine is characterized by an acidic pH value (2.99) and was geochemically analyzed by Petrounias et al. [26]. These results are given in Table 4. According to the results of Table 4, the wastewater contains an extremely high concentration of Cu (8847.21 ppb). Table 4. Chemical analysis of wastewater (-: below detection limit) [26].  Table 5 displays the final results of the chemical analyses of wastewater after having been passed four times through each column, in which the different mechanically activated serpentinites were used as filters. As displayed in Table 5, high amounts of Cu have been trapped from the samples that contain higher serpentinite contents. More specifically, the highly serpentinized sample (BE.01) seems to present a higher Cu removal capacity in comparison to the other three rock samples, even when used without having been mechanically activated, as well as when it was mechanically activated after 500, 1000 and 1500 revolutions, respectively.

Chemical X-ray Diffractometry of Serpentinites after the Experimental Study
The mechanically activated serpentinites (after 1500 revolutions), after having been used as filters in the experimental arrangement of the batch type columns for the removal of Cu, were analyzed by X-ray diffractometry. The corresponding X-ray diffraction patterns are given in Figure 6

Discussion
Several researchers have studied the individual use of minerals and of rocks materials in various environmental applications and more specifically for the removal of toxic loads using these materials [25,26]. Furthermore, quite many researchers have carried out mechanical, chemical and mechanochemical activation of minerals and rocks in order to increase their effectiveness in removing toxic loads from wastewater. Huang et al. [31] have concluded that mechanochemically activated serpentine presents very satisfactory results concerning Cu (II) removal (to an almost complete degree), allowing this type of removal to act as a way/method of recycling and reusing Cu derived from various wastewater solutions. Mechanical activation constitutes a way of applying mechanical stress to induce changes in the surface properties as well as in the crystalline structure of minerals [42][43][44][45]. Even though numerous studies relative to the understanding of the nature of the effect of mechanical loads on structural changes in the structure of minerals have been carried out, the activation of low cost phyllosilicate minerals, such as serpentine, has not yet been extensively investigated in environmental metal neutralization uses.
Petrounias et al. [26] combined sterile raw materials by using sterile aggregates of the LA test, and achieved significant removal of Cu from the Agios Philippos Kirkis mine (Greece). They attributed the Cu removal to the existence of mechanically activated serpentinite. This was carried out under pH 4 conditions, where precipitation of metal complexes is not favored [46]. In general, the pH of the solution controls the adsorption of Cu in the laminated serpentine, mainly of tetrahedral silicate during the ion exchange process.
This study, which is based on and expands the initial study of Petrounias et al. [26] attempted to find out, more accurately, the mechanism as well as the necessary and sufficient conditions for a

Discussion
Several researchers have studied the individual use of minerals and of rocks materials in various environmental applications and more specifically for the removal of toxic loads using these materials [25,26]. Furthermore, quite many researchers have carried out mechanical, chemical and mechanochemical activation of minerals and rocks in order to increase their effectiveness in removing toxic loads from wastewater. Huang et al. [31] have concluded that mechanochemically activated serpentine presents very satisfactory results concerning Cu (II) removal (to an almost complete degree), allowing this type of removal to act as a way/method of recycling and reusing Cu derived from various wastewater solutions. Mechanical activation constitutes a way of applying mechanical stress to induce changes in the surface properties as well as in the crystalline structure of minerals [42][43][44][45]. Even though numerous studies relative to the understanding of the nature of the effect of mechanical loads on structural changes in the structure of minerals have been carried out, the activation of low cost phyllosilicate minerals, such as serpentine, has not yet been extensively investigated in environmental metal neutralization uses.
Petrounias et al. [26] combined sterile raw materials by using sterile aggregates of the LA test, and achieved significant removal of Cu from the Agios Philippos Kirkis mine (Greece). They attributed the Cu removal to the existence of mechanically activated serpentinite. This was carried out under pH 4 conditions, where precipitation of metal complexes is not favored [46]. In general, the pH of the solution controls the adsorption of Cu in the laminated serpentine, mainly of tetrahedral silicate during the ion exchange process.
This study, which is based on and expands the initial study of Petrounias et al. [26] attempted to find out, more accurately, the mechanism as well as the necessary and sufficient conditions for a serpentinized ultramafic rock to work efficiently in selective Cu capture from wastewater. As presented in Table 5, it is obvious that as the mechanical stress increases (through the LA test), which means that as the loadings of abrasion and attrition increase, the capacity of the serpentinized rocks in capture Cu increases regardless their degree of serpentinization. Thus, this increase may happen exclusively due to the existence and the structure of serpentine. When serpentine is subjected to mechanical loading there is structural change, especially in the OH − group, which may become more relaxed than in the octahedral positions and easily circulate in solution when in contact with it [31]. When the structure of serpentine is decomposed by the use of abrasive mechanical stresses, is is unable to retain its atom structure and thus its crystallinity is altered. This change in the crystallinity of serpentine has been cited as one of the major factors for copper adsorption [26,31]. It is understood that mechanical stress may rupture the tetrahedral and octahedral sheets of serpentine. Moreover, intensively significant index relative to the capacity of Cu capture seems to be the degree of serpentinization of the rock materials used. More specifically, the more serpentinized ultramafic rocks (BE.01, ED.111B), as they have been identified through the petrographic observation (Figure 3), the X-Ray diffractometry and Rietveld method (Figure 4, Table 1) and the geochemical analysis given through the LOI index (Table 3), seem more effective in Cu capture (Table 5) relative to those contained less serpentine (BE.118, ED.86B). Moreover, the effectiveness, in the Cu capture, of the most serpentinized ultramafic rocks is indicated by the presence of wroewolfeite in the structure of these rocks after their use as filters ( Figure 6).
The amount of serpentine found in the studied rocks is presented as the determinant factor, as through this, the rate of change of available crystalline meshes capable of Cu capture from the studied solutions is determined. However, the combination of the abovementioned factors seems to constitute the more crucial combination concerning the effectiveness of each serpentinized lithotypes for the removal of Cu. More specifically, the highly serpentinized ultramafic rocks (BE.01, ED.111B with 88.6-91.7% of serpentine contained) present faster and more efficient capture of Cu in contrast to those characterized by lesser amounts of contained serpentine (BE.118, ED.86B with 59.0-70.0% of serpentine).
Furthermore, the Cu capture capacity seems to be related to the type of serpentine and therefore to the special texture characteristics of the studied serpentinites. More specifically, the serpentinized samples of similar degree of serpentinization (Table 1) but with a variety in textural features (mesh, ribbon) and in serpentine type (chrysotile, antigorite and lizardite), as shown in the corresponding diagrams ( Figure 5), display significant differences regarding their Cu capture effectiveness. Serpentine from highly serpentinized ultramafic rocks (Group I) plotted in the field of antigorite ( Figure 5) present as more capable of removing Cu in contrast those of Group II (medium serpentinized ultramafic rocks) whose serpentine is plotted in the field of lizardite and chrysotile. This may happen due to the different capacity of lizardite, chrysotile and antigorite for retaining their crystallinity under mechanical stress. Additionally, the petrographic characteristics such as texture may significantly influence the Cu capture. More specifically, the mesh texture of serpentine in the most serpentinized sample (BE.01) is presented as the most effective texture than the other textures of the rest studied rocks, a fact which may happen due to surface adsorption of Cu 2+ when CuOH − is simultaneously generated and adsorbed within the microcells.

Proposed Areas with Serpentinites for Their Potential Use as Filters for Cu Removal
Nowadays, in the era of cyclical economy and climate change, the ability to recover and reuse metals has been studied by many researchers [31,47]. Such research is fundamental to modern cutting-edge studies. In this study, the amount of Cu captured using serpentinites from the Veria-Naousa and Edessa ophiolite complexes suggest promising results to potentially recover copper accumulated within the crystallinity of serpentine (Figure 6), by using a variety of physicochemical recovery methods. The main object of the this work is to capture Cu within the crystallinity of serpentine from serpentinized ultramafic rocks and also to examine this application in conjunction with the recovery of copper from wastewater, as well as to propose potential areas that encompass serpentinized ultramafic rocks suitable for these applications (Figure 7). GIS-based petrographic mapping of serpentinites feasible to be used as raw materials for copper capture are suggested. In the modified maps (see below) we have taken into account all of the aforementioned factors and propose specific areas that are defined and measured from the examined ophiolite complexes (Figures 7 and 8). Specifically, the areas marked with dark green color (zone A) constitute the suggested areas from the mentioned complexes with the suitable serpentinites. These serpentinites can potentially be used as filters for Cu removal regarding their petrographic characteristics (degree of serpentinization, textural features and serpentine type) and geochemical characteristics (LOI index). The Veria-Naousa ophiolite complex comprises of Figure 7. Modified geological map of Veria-Naousa ophiolite complex [33] after fieldwork and mapping using ArcMap 10.1; the area of investigation is shown in the black rectangle; the dark green color shows the highly-serpentinized ultramafic rocks of the region and the light green color shows the medium-serpentinized ultramafic rocks.
GIS-based petrographic mapping of serpentinites feasible to be used as raw materials for copper capture are suggested. In the modified maps (see below) we have taken into account all of the aforementioned factors and propose specific areas that are defined and measured from the examined ophiolite complexes (Figures 7 and 8). Specifically, the areas marked with dark green color (zone A) constitute the suggested areas from the mentioned complexes with the suitable serpentinites. These serpentinites can potentially be used as filters for Cu removal regarding their petrographic characteristics (degree of serpentinization, textural features and serpentine type) and geochemical characteristics (LOI index). The Veria-Naousa ophiolite complex comprises of highly-serpentinized ultramafic rocks, and GIS-based calculations yield an area of 43.84 km 2 , whereas the Edessa ophiolite complex is calculated to be 42.19 km 2 (Figure 7). On the other hand, zone B, marked with light green color, constitutes the lesser suitable areas for Cu capture, as they contain lower amounts of serpentine and different mineralogical and petrographic characteristics than those of zone A.
Energies 2020, 13, x FOR PEER REVIEW 17 of 20 highly-serpentinized ultramafic rocks, and GIS-based calculations yield an area of 43.84 km 2 , whereas the Edessa ophiolite complex is calculated to be 42.19 km 2 (Figure 7). On the other hand, zone B, marked with light green color, constitutes the lesser suitable areas for Cu capture, as they contain lower amounts of serpentine and different mineralogical and petrographic characteristics than those of zone A. Concerning the Veria-Naousa ophiolite complex, 2.93 km 2 of highly serpentinized ultramafic rocks was calculated using GIS method, whereas in the Edessa ophiolite complex 8.15 km 2 was calculated ( Figure 8). Conclusively, the highly serpentinized ultramafic rocks from both ophiolite complexes are present in higher volumes than those of the medium-serpentinized rocks.  [39] after fieldwork and mapping using ArcMap 10.1; the area of investigation is shown in the black rectangle; the dark green color shows the highly-serpentinized ultramafic rocks of the region and the light green color shows the medium-serpentinized ultramafic rocks.
Concerning the Veria-Naousa ophiolite complex, 2.93 km 2 of highly serpentinized ultramafic rocks was calculated using GIS method, whereas in the Edessa ophiolite complex 8.15 km 2 was calculated ( Figure 8). Conclusively, the highly serpentinized ultramafic rocks from both ophiolite complexes are present in higher volumes than those of the medium-serpentinized rocks. Additionally, through the proposed maps, which are first introduced through this study, an extra use for these serpentinites is proposed apart from aggregates for construction and environmental applications as has already highlighted by Petrounias et al. [48,49].

Conclusions
In this paper, the selective capture of Cu (II) from acidic wastewater derived from the pit lakes of the Agios Philippos mine (Greece) from mechanically activated serpentinite using a LA machine was studied. The abovementioned study leads to the following conclusions: • Two groups of serpentinized ultramafic rocks from the investigated ophiolite complexes which were detected according to their petrographic observations were in accordance with their mineralogical, chemical and geochemical analyses.

•
The highly serpentinized rocks (Group I) are more effective in Cu removal in contrast to the medium serpentinized rock samples (Group II).

•
The higher mechanical activation of the studied serpentinites (after they have been subjected to a 1500 revolutions LA test) is related to their higher capability to perform Cu removal. • Selective removal of Cu (II) in the form of the wroewolfeite phase was achieved by using mechanically activated highly serpentinized ultramafic rocks.
Furthermore, areas with highly serpentinized ultramafic rocks that can potentially be used as filters for the effective Cu (II) removal from industrial wastewater are suggested and more specifically these are the 43.84 km 2 areas from the Veria-Naousa ophiolite and the 42.19 km 2 area from the Edessa ophiolite.