This study has focused on the characterization, recovery and treatment of apple processing wastes, which are important in terms of sustainability and circular economy. Apple processing wastewater (AW) was noted for its acidity (pH 4.2), high chemical oxygen demand (COD) (114 g/L), total solids (TS; 13.5 %) and oil/grease content (16.5 g/L), as well as the presence of valuable fatty acids and phenolics. Total phenolic content (TPC), total flavonoids content (TFC) and antioxidant activity were determined in the wastewater as 1660 mg GAE/L, 421 mg QE/L and 2.1 mM TE, respectively. The extraction of phenolic compounds from AW and apple pomace (AP) using supercritical carbon dioxide (SC–CO2) extraction was investigated as a first step. The results indicate that SC–CO2 extraction is effective in recovering phenolic compounds from apple processing wastes. The extraction yields for AW and AP using SC–CO2 reached up to 76 % and 43 % of the extractable oils, respectively. Recovery efficiencies of the TPC were observed to be up to 3.8 % for AW and 11.4 % for AP. Furthermore, the phenolic and fatty acid profiles of extracts were also evaluated, indicating the recovery of valuable compounds such as quercetin, catechin, procyanidin B2, ω–6 and ω–9 fatty acids. In terms of wastewater treatment, the use of ozone oxidation (OO) and supercritical water oxidation (SCWO) for the removal of COD, suspended solids (SS), TPC and toxicity from AW were also investigated. The OO exhibited relatively low COD removal efficiency, while SCWO demonstrated high efficiency ranging from 84 % to 99.8 %. This study has revealed that while SCWO effectively removes COD, TPC, SS and color from fruit processing wastewater, OO demonstrates greater effectiveness in reducing toxicity in the Vibrio fischeri test.

中文翻译：

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苹果加工废料的零废弃物应用：通过超临界 CO2 回收有价值的化合物，通过高级氧化进行废水处理


本研究的重点是苹果加工废料的表征、回收和处理，这在可持续性和循环经济方面非常重要。苹果加工废水 （AW） 因其酸度 （pH 4.2）、高化学需氧量 （COD） （114 g/L）、总固体 （TS;13.5 %）和油/油脂含量 （16.5 g/L） 以及有价值的脂肪酸和酚类物质的存在而著称。测定废水中总酚含量 （TPC）、总黄酮含量 （TFC） 和抗氧化活性分别为 1660 mg GAE/L、421 mg QE/L 和 2.1 mM TE。第一步是使用超临界二氧化碳 （SC-CO2） 萃取从 AW 和苹果渣 （AP） 中提取酚类化合物。结果表明，SC-CO2 萃取可有效回收苹果加工废料中的酚类化合物。使用 SC-CO2 的 AW 和 AP 的萃取率分别达到可萃取油的 76% 和 43%。观察到 AW 的 TPC 回收效率高达 3.8%，AP 的回收效率高达 11.4%。此外，还评估了提取物的酚类和脂肪酸谱，表明回收了有价值的化合物，如槲皮素、儿茶素、原花青素 B2、ω-6 和 ω-9 脂肪酸。在废水处理方面，还研究了臭氧氧化 （OO） 和超临界水氧化 （SCWO） 去除 COD、悬浮固体 （SS）、TPC 和 AW 的毒性。OO 表现出相对较低的 COD 去除效率，而 SCWO 表现出 84% 至 99.8% 的高效率。这项研究表明，虽然 SCWO 有效地去除了水果加工废水中的 COD、TPC、SS 和颜色，但 OO 在费氏弧菌测试中表现出更高的毒性效果。