[en] Abstract At the present time, all industrial processes produce wastes whose management is a major challenge to protect the planet. Biomachining is a biotechnological process that uses microorganisms to obtain new products and, just like any other technology, it generates wastes. Biomachining allows metallic (copper) pieces to be machined biochemically, whilst chemical oxidant is continuously regenerated by microorganisms. Nevertheless, the metal concentration (copper) in the solution will increase throughout time and this will halt the biomass activity. When the solution loses its capacity to regenerate the chemical oxidant, it is considered to be depleted and the suspended microorganisms have to be removed from the solution by filtration. Subsequently, the liquid must be treated or "cleaned". The main objective of this work is to study two alternatives to recover copper from the waste solution generated in the biomachining process; namely, fractionated precipitation and electrochemical recovery. Thus, this waste solution could be considered a "source" (rather than a waste), its treatment could be environmentally friendly and, consequently, the implementation of this biotechnology at industrial level could be enhanced. In order to carry out the laboratory experiments, a synthetic medium simulating real depleted solutions was prepared (in real solutions a previous filtration of the microorganisms is required). After dissolving the major components (CuSO4, FeSO4 and (NH4)2SO4), pH was acidified to avoid metal losses due to jarosite precipitation. Next, hydrogen peroxide (H2O2) was added to oxidise ferrous ions (Fe2+) into ferric ions (Fe3+) before proceeding to the main treatment. Regarding fractionated precipitation, the pH of the solution was increased in two steps using sodium hydroxide (NaOH); first, iron was precipitated at pH 4,0, and then, copper, at pH 11,0. After the first pH increase, more than 99,5% of the total iron was removed from the solution, while copper loss was deemed negligible. The calcined precipitate obtained in this step was identified as synthetic hematite (Fe2O3) (its market value is not remarkable). When the pH value was increased to 11,0 for copper precipitation, the metal removal from the solution achieved in this step was also higher than 99,5%. v The precipitate obtained was calcined and identified as tenorite, yielding 10,02 g tenorite (CuO) per liter solution. The metal (Fe3+ and Cu2+) concentration remaining in the final solution was very low, despite sulfide content being fairly high. NaOH was the only chemical required in this treatment and the most relevant cost was related to the energy consumption during calcination process of the precipitates (3 €/L). Regarding the electrochemical recovery of copper, the pH of the solution had to be increased to 4,0 before electrolysis was performed. This requirement was justified on the basis that when Cu2+concentration in solution is higher than 1 g/L Cu2+, Fe3+ ion presence is known to boost the electric consumption and hinder copper recovery. More than 97% of copper was removed from the solution, both at constant current and constant voltage experiments, rendering a final production of 7 g Cuo/L. The product obtained (Cuo) had a reasonable value at the secondary raw materials market. Nevertheless, energy consumption was very high (15,7 €/L), and revenues obtained from selling this product do not cover treatment expenditures. The recovery efficiency of copper by fractionated precipitation and electrolysis was very high. The simple equipment required, the low metal concentration in the final solution and the need to previously precipitate iron are common features of the two alternatives studied in this work. Despite the two products ́ market value being very much alike, the energy consumption of the electrochemical recovery was 5-fold higher in comparison to the fractionated precipitation. Therefore, the latter was concluded to be the most viable option. Further studies on other treatment alternatives could include the filtration of these solutions through biopolymeric based membranes. Thus, being complementary to this study, another experimental work focused on this promising technique is currently under development.

[eu] Laburpena Gaur egun, industria prozesu guztietan hondakinak sortarazten dira eta hondakin horiek zuzen tratatzea eta kudeatzea gizartearen erronka handia da. Produktu desberdinak ekoizteko mikroorganismoak erabiltzen dituzten prozesu bioteknologikoen artean, biomekanizazioa aipa daiteke, eta beste teknologia batzuetan bezala, honetan ere hondakinak sortarazten dira. Mekanizazio biologikoan, metalezko (kobrezko) piezak era biokimikoan mekaniza daitezke, mikroorganismoek oxidatzaile kimikoa etengabe birsortuko dutela. Baina, disoluzioan metalaren (kobrearen) kantitatea gero eta handiagoa izango da eta horrek biomasaren aktibitatea kaltetuko du. Disoluzio horrek oxidatzaile kimikoa birsortzeko ahalmena galtzen duenean (eta beraz agortu egiten denean), lehendabizi iragazi egin behar da suspentsioan dauden mikroorganismoak kentzeko, eta gero likidoa tratatu edo "garbitu" egin behar da. Isuri baino lehenago, oso metal baliotsua den kobrea berreskuratzeko aukera bi aztertu dira lan honetan. Beraz, lan honen helburu nagusia, biomekanizazio prozesuen hondar-disoluzioetatik kobrea berreskuratzeko alternatiba bi aztertzea da; hala nola, hauspeakuntza zatikatua eta berreskurapen elektrolitikoa. Horrela, bioteknologia horretan sortarazitako hondakina, alde batetik, errekurtsoa izan dadin eta bestetik tratamendu jasangarria eduki dezan ekarpena egin nahi da. Bidez batez, bioprozesu horrek industria mailan aplikatzeko dituen oztopoetariko batzuk gainditzeko irtenbidea eskainiko da. Laborategiko entseguak burutzeko, biomekanizazioan agorturiko disoluzioak simulatzen dituen ingurune sintetikoa prestatu da (disoluzio errealaren kasuan aurretik mikroorganismoak iragazi egin beharko ziren). Gehiengo konposatuak (CuSO4, FeSO4 eta (NH4)2SO4) disolbatu ostean, pH-a azidifikatu da, hauspeakin (jarosita) erako galerak ekiditeko. Jarraian, hidrogeno peroxidoa (H2O2) erabiliz, ioi ferrosoa (Fe2+) ioi ferrikora (Fe3+) oxidatu da, ondorengo tratamenduak aplikatu ahal izateko. Hauspeakin zatikatuari dagokionez, hondar-disoluzioaren pH-a bi pausotan igo da sodio hidroxidoaren (NaOH) erabiliz; lehendabizi, 4,0-ra burdina hauspeatzeko, eta gero, 11,0-ra kobrea hauspeatzeko. Lehenengo pH-aren aldaketari esker, burdinaren % 99,5a baino kantitate handiagoa ezabatu da disoluziotik, kobrearen galera mespretxagarria izanik. Pauso honetako hauspeakina kaltzinatu ostean lortutako konposatua hematita sintetikoa (Fe2O3) izan da (produktu horren merkatu balioa ez da adierazgarria). Beste alde batetik, pH-a 11,0 denean, kobrearen ezabapena ere kuantitatiboa (% 99,5a baino altuagoa) izateaz gain, balio ekonomikoa duen kobrezko konposatu bat lortu da; hau da, hondakin disoluzio litroko 10,02 g tenorita (CuO) lortu dira. Amaierako disoluzioan geratzen diren metalen (Fe3+ eta Cu2+) kontzentrazioa oso baxua izatea lortu da, nahiz eta sulfatoen edukia oraindik ere altua izan. Tratamendu aukera honetan, erabiltzen den erreaktibo bakarra NaOH da, eta gastu energetikorik altuena kaltzinazio-prozesuari dagokio (3 €/L). ii Elektrolisiaren bidezko kobre berreskurapenari dagokionez, lehenengo pausoa burdina hauspeatzea da, pH-aren balioa 4,0ra igota. Izan ere, 1 g Cu2+/L baino gehiago duten disoluzioen kasuan, burdina aurretik hauspeatu behar da derrigorrez, Fe3+ katioien presentziak energia elektrikoaren kontsumoa igotzen duelako eta disolbaturiko kobrearen berreskurapena oztopatzen duelako. Korronte intentsitate konstantepeko saiakuntzetan zein tentsio konstantepeko saiakuntzetan antzeko emaitzak lortu dira; kasu bietan berreskuratutako kobrearen kantitatea % 97a baino altuagoa izan da; hots, 7 g Cuo litroko. Prozesu honetan lortutako azpiproduktua, bigarren mailako lehengaien merkatuan saltzeko balio duen kobre elementala izan da, baina elektrizitatearen gastua altua izan da (15,7 €/L). Biomekanizazioaren disoluzio agortuak tratatzeko hauspeakuntza zatikatua zein elektrolisia aplikatuta, kobrearen berreskurapen efizientzia oso altua izan da. Kasu bietan, ekipamendua sinplea da eta bukaerako disoluzioen metalen edukia oso baxua, aldez aurretiko burdinaren hauspeakuntza derrigorrezko pauso komuna izanik. Antzeko balio ekonomikoa duten kobrezko produktu bi lortu arren, elektrolisiaren gastu energetikoa 5 aldiz handiagoa da beste aukerarena baino. Ondorioz, hauspeakuntzaren bidezko berreskurapena tratamendurik bideragarriena da. Disoluzio agortuak tratatzeko etorkizun handiko beste aukera batzuk ere badaude; esate baterako, oinarri biopolimerikoa duten mintzetan zeharreko iragazketa. Teknika hori da bereziki lan honen jarraipena den beste GrAL baten ikerkuntz-gaia da.