Optimal process parameters for removal of phenolic compounds from olive mill wastewater by electrocoagulation method

Proces obrade otpadne vegetacijske vode masline (OMW) je jedan od glavnih ekoloških problema u Mediteranskim gradovima. Otpadna voda sadrži razne organske spojeve kao što su dugolančane masne kiseline te fenolne komponente, koje imaju negativan utjecaj na okoliš. U ovom radu su povedena ispitivanja uklanjanja fenolnih spojeva iz OMW procesom elektrokoagulacije uz dodatak NaCl (cNaCl=0,25 mol dm^-3). Ovi dodaci povećavaju električnu provodnost otopine te je na taj način smanjena ukupna potrošnja električne energije. S obzirom da se problem obrade vegetacijske vode masline odvija u priobalnom području otpadnu vodu je moguće ispustiti u more pri čemu kloridi neće predstavljati opasnost za okoliš. U radu su korištene elektrode od željeza. Ispitani su razni utjecaji parametara na proces, kao što su vrijeme obrade procesa, pH vrijednosti i struja. Početna pH vrijednost je varirala od 3-7 pri čemu je utvrđeno je da djelotvornost procesa pada s povećanjem pH vrijednosti s 69% na 46% što je povezano s formiranjem kompleksnih spojeva. S povećanjem vremena provedbe procesa s 30 na 60 minuta djelotvornost je porasla s 58% na 68%, a s povećanjem struje od 0,1 A na 0,4 A djelotvornost je narasla s 23% na 68% pa se može zaključiti da djelotvornost uklanjanja fenolnih spojeva također raste s porastom struje i vremena provedbe procesa. Metodom cikličke voltametrije ispitana je otopina OMW, a uz to je kao kontrolna otopina korištena otopina ELM koja sadrži slične fenolne spojeve kao i OMW. Ispitivanje je provedeno da bi se utvrdila mogućnost korištenja ove metode kod određivanja fenolnih spojeva i da bi se eventualno dokazalo nastajanje kompleksnih spojeva. Formiranje kompleksnih spojeva se pokušalo dokazati i korištenjem UV/Vis spektroskopije u otopini ELM u koju su dodani ioni Fe3+.The treatment of olive oil mill wastewater (OMW) is one of the most important environmental problems in the Mediterranean countries. The wastewater includes organic chemicals such as long-chain fatty acids and phenolic compounds, which have negative impact on the environment. In this work, electrocoagulation treatment of olive mill wastewater is applied for removal of phenolic compounds by addition of NaCl (cNaCl=0,25 mol dm^-3). The NaCl additions increased conductivity of solution and thus reduced electric energy consumption. Since most olive oil production plants are situated on the Mediterranean coastline, additions of NaCl and the disposal of the treated effluent containing NaCl into the sea is acceptable. Carbon steel electrodes were used in the experiments. The effects of key factors on electrocoagulation process have been investigated, such as treatment time, pH value and current. The initial pH value was in the range from 3 to 7. The removal efficiency decreased with increase of pH which is associated with the formation of complex phenolic compounds. By increase of treatment time removal efficiency increased from 58% (30 min) to 68% (60 min), and by increasing current (0,1 A to 0,4 A) removal efficiency increased from 23% to 68%. Therefore it can be concluded that phenolic compounds removal efficiency increased with current and treatment time increase. Using cyclic voltammetry method OMW and olive leaf extract (ELM) solutions were tested. ELM solution was used since similar phenolic compound are expected to be present within the solution. The measurements were carried out in order to study the possibility of using this method for phenolic compound analysis and to determine formation of complex. UV-Vis spectroscopy was used as additional method to determine complex formation between Fe3+ and phenolic compounds