Abstract
Jordanian bentonite was activated by hydrochloric acid at room temperature. FTIR, XRD, TGA, and BET surface area analyses of the samples were carried out to examine the structure of bentonite before and after acid activation. It is found that the octahedral cations were removed, which altered the chemical composition of the bentonite. Difference of surface area was noticed (66.2 to 287.8 m2 g−1), which was caused by structural changes in the bentonite. We aimed to investigate the effectiveness of activated bentonite in OMWW treatment. Batch and column techniques were applied. Crude and treated OMWW samples were characterized; physiochemical parameters, total phenolic compounds, and heavy metal ions concentrations were measured. Several parameters that affected the adsorption capacity were studied: the pH value of the solution, temperature, and the adsorbent dose. It was found that the maximum removal of total phenolic compounds and heavy metal ions (Zn, Fe, and Mn) was at pH 6. Adsorption capacity of phenolic compounds was enhanced with an increase in the temperature of the solution and also with the adsorbent dose. The optimum adsorbent concentration needed for the maximum removal of total phenolic compounds is 1 g of activated bentonite/0.01 L of OMWW. The percentage removal exceeded 99% for Zn, Fe, and Mn ions, while it reached 65.2 and 61.5 for K+ and Na+ ions, respectively. Finally, the percentage removal of pollutants was increased by using activated bentonite. This study will provide valuable insight into the effect of activated bentonite towards the treatment and recyclability of OMWW, which is essential for the local olive mill industry.
Highlights
The production of olive oil has been a well-known and established practice in the Mediterranean region for hundreds of years
OMWW is produced in Jordan and Mediterranean regions in huge amounts and results in heavily polluted waste water that causes negative environmental impacts
Untreated OMWW is characterized by a high content of phenolic compounds, some heavy metals, and other salts
Summary
The production of olive oil has been a well-known and established practice in the Mediterranean region for hundreds of years. OMWW contains an appreciable content of phenolic compounds, consisting of monocyclic aromatic molecules, such as tyrosol, catechol, and caffeic acid [3] It contains a considerable content of inorganic compounds, such as heavy metals, phosphorus, potassium, and nitrogen [4]. Its uncontrolled disposal into water sources leads to severe problems for the whole ecosystem and especially for natural water life If it is disposed directly onto soil, it damages the properties of the soil, and it can be toxic for microorganisms, algae, plants, and insects [5]. Increasing the concentration of nitrogen generally has a negative effect on microbial biomass in soil, such as direct inhibition, resulting in soil imbalance It affects some plants and often they die [8]
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