Hydrothermal treatment of pig manure for the catalytic production of nitrogen-phosphorus-potassium (NPK)-rich artificial humic acid and full utilisation of residue adsorption

• Published in: Journal of environmental chemical engineering 2024-12, Vol.12 (6), p.114793, Article 114793
• Main Authors: Qi, Jiamin, Yin, Shunyu, Bian, Haohao, Fan, Xing, Huang, Junhao, Yang, Bo, Zhu, Hengxi, Kong, Dehui, Zhang, Yi, Yang, Chao, Li, Yizhao, Zhou, Zhenxing, Liu, Zewei, Zhang, Jin, Su, Xintai, Li, Bin
• Format: Article
• Language: English
• Subjects: Adsorbtion; Congo red; Hydrothermal process; Pig manure; Potassium humate
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.114793

Pig manure (PM) poses notable environmental and economic challenges as a significant agricultural waste. This study explores the catalytic oxidation of PM to produce potassium humate (HAK) using copper oxide (CuO) as a catalyst under hydrothermal conditions. Optimal parameters were identified as 10 % KOH addition, 0.01 g CuO catalyst, a hydrothermal temperature of 150 °C, and a reaction time of 3 hours, achieving an HAK yield of 82.54 %. Characterization techniques confirmed PM's effectiveness as a precursor and clarified CuO's role in enhancing conversion by increasing oxygen-containing functional groups. Nutrient recovery experiments showed that the combined addition of CuO and KOH led to recovery rates for nitrogen (N), phosphorus (P), and potassium (K) exceeding 98 %. The CuO catalyst increased P content by converting it into stable forms suitable for slow-release fertilizers, while enhancing N functionality through processes like the Maillard reaction and transforming K into beneficial forms for soil fertility. Additionally, the residues from the HAK production process were modified for use as an adsorbent (400-PMR-10) in dye wastewater treatment, demonstrating over 90 % removal efficiency for Congo red dye, even after multiple cycles. In summary, this research offers a sustainable approach to valorizing PM, yielding high quantities of HAK while utilizing residues for environmental remediation, contributing to improved soil fertility and effective wastewater treatment, and providing significant environmental and agricultural benefits. [Display omitted] •Addressed environmental and economic challenges posed by pig manure (PM) waste.•Catalytic oxidation of PM using CuO catalyst to produce potassium humate (HAK).•Achieved nutrient recovery (N, P, K) rates exceeding 98 % with catalyst and KOH.•CuO catalyst enhanced phosphorus content and nitrogen functionality in HAK production.•Residual PMR was modified into an effective adsorbent for dye wastewater treatment.