Modification of biochar prepared from olive oil processing waste to enhance phenol removal from synthetic and olive mill wastewater

Evaluating the fixed-bed column adsorption capacity of olive pomace biochar activated with KOH and H3PO4 for olive mill wastewater treatment: Insights from TOC and HPLC analysis

This study explores the treatment of olive mill wastewater (OMWW) using activated carbon derived from olive mill solid waste (OMSW). The OMSW was first converted into biochar on a pilot scale and then activated using potassium hydroxide (KOH) and phosphoric acid (H3PO4). Characterization revealed that AC/KOH had a higher BET surface area (829 m2 g-1) than AC/H3PO4 (749 m2 g-1). Fixed-bed column experiments showed breakthrough times of 250 min for AC/KOH and 220 min for AC/H3PO4. The adsorption capacities determined by the Thomas model were 275.9 mg g-1 for total phenolics (TP), 774.7 mg g-1 for total organic carbon (TOC) with AC/KOH, and 309.1 mg g-1 for TP, 823.5 mg g-1 for TOC with AC/H3PO4. The Adams-Bohart model showed kinetic constants (KAB) of 0.332 for TP and 3.66∗10-5 for TOC with AC/KOH, compared to 0.1926 for TP and 2.21∗10-5 for TOC with AC/H3PO4. The Yoon-Nelson model indicated τ50 % values of 171.57 min for TP 60.39 min for TOC with AC/KOH, 111.79 min for TP, and 41.75 min for TOC with AC/H3PO4. High-performance liquid chromatography (HPLC) analysis revealed hydroxytyrosol concentration decreased from 4.9 g.L-1 to 0.37 g.L-1 with AC/H3PO4 and 0.42 g.L-1 with AC/KOH. The total phenolic concentration reduced from 5.57 g.L-1 in untreated OMWW to 0.66 g.L-1 with AC/H3PO4 and 0.84 g.L-1 with AC/KOH. These results demonstrate that both activated carbons effectively reduce phenolic concentrations. This study achieves some of the highest adsorption capacities reported for OMWW treatment, this technique demonstrates the outstanding performance of the developed materials. Unlike most research, which focuses on static conditions, less than 10 % of studies explore dynamic fixed-bed setups, underscoring the novelty of this work. The materials can be easily integrated into conventional treatment processes, providing a cost-effective and sustainable solution. By utilizing byproducts from the olive oil industry to treat its wastewater, the approach creates a closed-loop system. Furthermore, the activated carbons are regenerable and reusable, enhancing their practicality while enabling the recovery of valuable polyphenols for added resource valorization.

Response of chemical and biochemical soil properties to the spreading of biochar-based treated olive mill wastewater

Despite the polluting potential olive mill wastewater (OMW) can be a useful source of nutrients and organic compounds to improve soil properties. The aim of this paper was to verify if biochar-based treatment of OMW could be an efficient method to contrast the richness in phenolic compounds and phytotoxicity of OMW making it more suitable. for soil amendment. In this study poplar biochar (BP) was more effective than conifer biochar (BC) in terms of adsorbing phenols and reducing phytotoxicity at different biochar rates (5 and 10 %). In soil amendment BP-treated OMW induced an increase of organic carbon by approximately 15 % and notably BP10 treated OMW enhanced available phosphorous by 25 % after 30 days of incubation. In soil amended with 10 % BP-treated OMW microbial biomass and enzymatic activities were significantly enhanced after 30 and 90 days, with no effect on cress seed germination. Therefore, biochar based-treatment could be cost-effective and able to facilitate the long-term management of OMW in terms of storage and disposal.

Olive mill wastes: from wastes to resources

Olive oil extraction has recently experienced a continuous increase due to its related beneficial properties. Consequently, large amounts of olive mill wastes (OMWs) derived from the trituration process are annually produced, causing serious environmental problems. The limited financial capabilities of olive mills make them usually unable to bear the high costs required for the disposal of their wastes. Alternatively, the valorization of OMWs within the framework of the so-called waste-to-resource concept and their recycling can represent a successful strategy for the implementation of circular economy model in the olive industry, which could have significant socioeconomic impacts on low-income Mediterranean countries. There is, however, no unique solution for OMWs valorization, due to the wide variety of the wastes' composition and their seasonal production. In this review, the potential of OMWs for being reused and the recent technological advances in the field of OMWs valorization are assessed. Special focus is given to the analysis of the advantages and limitations of each technology and to reporting the most significant issues that still limiting its industrial scale-up. The information collected in this review shows that OMW could be effectively exploited in several sectors, including energy production and agriculture. OMWs potential seems, however, undervalued, and the implementation of sustainable valorization strategies in large-scale remains challenging. More efforts and policy actions, through collective actions, encouraging subsidies, and establishing public-private collaborations, are still needed to reconcile research progress with industrial practices and encourage the large-scale implementation of the waste-to-resource concept in the olive sector.

Response of chemical and biochemical soil properties to the spreading of biochar-based treated olive mill wastewater

Olive mill wastewater (OMW) is the effluent derived from the oil extraction processes from olives. Despite the polluting potential OMW can be a useful source of nutrients and organic compounds to improve soil properties. OMW could negatively affect soil and water quality as this waste is rich in phenolic compounds and has high COD and BOD5. Biochar-based treatment could be an efficient method to remediate OMW. In this study poplar biochar (BP) was more effective than conifer biochar (BC) in terms of adsorbing phenols and reducing phytotoxicity at different biochar rates (5 and 10 %). BP-treated OMW was used in soil amendment and induced an increase in chemical properties, especially in organic carbon after 30 days of incubation. In soil amended with 10 % BP-treated OMW microbial biomass, enzymatic activities, and cress seed germination were significantly enhanced after 30 and 90 days.

Materials Derived from Olive Pomace as Effective Bioadsorbents for the Process of Removing Total Phenols from Oil Mill Effluents

This work investigates olive pomace from olive mill factories as an adsorbent for the removal of total phenols from olive mill effluent (OME). This pathway of valorization of olive pomace reduces the environmental impact of OME while providing a sustainable and cost-effective wastewater treatment approach for the olive oil industry. Olive pomace was pretreated with water washing, drying (60 °C) and sieving (<2 mm) to obtain the raw olive pomace (OPR) adsorbent material. Olive pomace biochar (OPB) was obtained via carbonization of OPR at 450 °C in a muffle furnace. The adsorbent materials OPR and OPB were characterized using several basic analyzes (Scanning Electron Microscopy-Energy-Dispersive X-ray SEM/EDX, X-ray Diffraction XRD, thermal analysis DTA and TGA, Fourier transform infrared FTIR and Brunauer, Emmett and Teller surface BET). The materials were subsequently tested in a series of experimental tests to optimize the sorption of polyphenols from OME, investigating the effects of pH and adsorbent dose. Adsorption kinetics showed good correlation with a pseudo-second-order kinetic model as well as Langmuir isotherms. Maximum adsorption capacities amounted to 21.27 mg·g-1 for OPR and 66.67 mg·g-1 for OPB, respectively. Thermodynamic simulations indicated spontaneous and exothermic reaction. The rates of total phenol removal were within the range of 10-90% following 24 h batch adsorption in OME diluted at 100 mg/L total phenols, with the highest removal rates observed at pH = 10. Furthermore, solvent regeneration with 70% ethanol solution yielded partial regeneration of OPR at 14% and of OPB at 45% following the adsorption, implying a significant rate of recovery of phenols in the solvent. The results of this study suggest that adsorbents derived from olive pomace may be used as economical materials for the treatment and potential capture of total phenols from OME, also suggesting potential further applications for pollutants in industrial wastewaters, which can have significant implications in the field of environmental technologies.

Transition towards Sustainable Carwash Wastewater Management: Trends and Enabling Technologies at Global Scale

Carwash wastewater (CWW) contains grease, oil, hydrocarbon residues, heavy metals, and surfactants, posing severe impacts to the environment and human health. Accordingly, various physical, chemical, and biological processes for CWW treatment have been demonstrated in recent research. In this study, a bibliometric approach was performed to comprehensively illustrate the recent progress, current direction, and future perspectives of CWW-related research. A keyword co-occurrence network was used to represent the results of the bibliometric analysis and to show the major pollutants in CWW effluents and the common systems for treating CWW via coagulation/flocculation, electrochemical, oxidation, membrane, adsorption, biological, and hybrid methods. An integrated anaerobic digestion/oxidation process has been reported to degrade CWW-associated pollutants and help develop an energy-efficient approach for waste management. The results demonstrated that the treatment of CWW has several benefits relevant to sustainable development, viz., good health and well-being, protection of life below water, bioenergy generation, and community awareness and acceptance towards wastewater reuse. Hence, these benefits could assist in meeting the environmental, economic, and social sustainable development goals (SDGs). These study outputs can encourage policymakers and stakeholders in implementing sensible regulations that control water usage and treatment in car sharing and personal vehicle services to either directly or indirectly adopt the agenda 2030 with its seventeen SDGs.

A critical review of state-of-the-art electrocoagulation technique applied to COD-rich industrial wastewaters

Electrocoagulation (EC) is one of the emerging technologies in groundwater and wastewater treatment as it combines the benefits of coagulation, sedimentation, flotation, and electrochemical oxidation processes. Extensive research efforts implementing EC technology have been executed over the last decade to treat chemical oxygen demand (COD)-rich industrial wastewaters with the aim to protect freshwater streams (e.g., rivers, lakes) from pollution. A comprehensive review of the available recent literature utilizing EC to treat wastewater with high COD levels is presented. In addition, recommendations are provided for future studies to improve the EC technology and broaden its range of application. This review paper introduces some technologies which are often adopted for industrial wastewater treatment. Then, the EC process is compared with those techniques as a treatment for COD-rich wastewater. The EC process is considered as the most privileged technology by different research groups owing to its ability to deal with abundant volumes of wastewater. After, the application of EC as a single and combined treatment for COD-rich wastewaters is thoroughly reviewed. Finally, this review attempts to highlight the potentials and limitations of EC. Related to the EC process in batch operation mode, the best operational conditions are found at 10 V and 60 min of voltage and reaction time, respectively. These last values guarantee high COD removal efficiencies of > 90%. This review also concludes that considerably large operation costs of the EC process appears to be the serious drawback and renders it as an unfeasible approach for handling of COD rich wastewaters. In the end, this review has attempted to highlights the potential and limitation of EC and suggests that vast notably research in the field of continuous flow EC system is essential to introduce this technology as a convincing wastewater technology.

Influence of Synthesis Methods on the High-Efficiency Removal of Cr(VI) from Aqueous Solution by Fe-Modified Magnetic Biochars

Fe-modified biochars have been widely used in removal of Cr(VI) from water due to the resulting modified surface functional groups and magnetization property. However, few studies have synthetically investigated modification methods and synthesis parameters on the improvement of the removal efficiency of Cr(VI) by Fe-modified biochars. Herein, 10 types of corn straw-based magnetic biochars were produced using pre-modification and post-modification methods with various modifier ratios, and the highest heating temperature (HHT). Cr(VI) removal results suggest that the removal efficiency of pre-modified biochars ranged from 50.7 to 98.6%, which was much higher than that of post-modified (6.6-21.6%) and unmodified biochars (0.4-7.6%). The effect of synthesis methods on Cr(VI) adsorption was in the following order: Fe-modification method > modifier ratio > HHT. The adsorption kinetics and isotherm results of three types of pre-modified biochars were well fitted with the pseudo-second-order model (R ² > 0.99) and the Langmuir adsorption model (R ² > 0.99), respectively, indicating the surface homogeneity of the pre-modified biochars and unilayer chemisorptions of Cr(VI). Characterization results show that iron oxides or zerovalent iron particles were successfully deposited onto the surface of biochars and magnetism was introduced. A good Pearson correlation (r = -0.9694) between the removal efficiency and pH value in modified biochar suggests that the lower pH value may offer more positive charges and promote electrostatic attraction. Therefore, the dominant mechanism for enhanced Cr(VI) adsorption on pre-modified biochar was electrostatic attraction, resulting from its distinguished acidity nature. Our findings provide new insights into the high-efficiency removal of Cr(VI) onto Fe-modified magnetic biochars and will benefit future design of more efficient magnetic biochars.