Thermally modified bamboo-eggshell adsorbent for phosphate recovery and its sustainable application as fertilizer

• Published in: Environmental research Vol. 231; no. Pt 1; p. 115992
• Main Authors: Sarker, Protima, Liu, Xin, Hata, Naoki, Takeshita, Hiroki, Miyamura, Hiroshi, Maruo, Masahiro
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 15.08.2023
• Subjects: Adsorption; Animals; Calcined eggshell; Desorption; Egg Shell - chemistry; Fertilizer; Fertilizers - analysis; Hydrogen-Ion Concentration; Kinetics; Natural adsorbent; Phosphates - analysis; Phosphorus removal; Plant growth; Wastewater; Water Pollutants, Chemical - analysis; Phosphorus removal; Adsorption; Plant growth; Natural adsorbent; Desorption; Calcined eggshell; Fertilizer
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.115992

Phosphate recovery from wastewater using readily available biowaste-based adsorbents is beneficial for both eutrophication control and waste management. Bamboo char has a high-density porous structure and eggshell contains CaCO3 with high affinity for phosphate. The combination of calcined bamboo and eggshell is a potential adsorbent for P recovery that has not been tested previously. Because bamboo char and eggshell both are popular for soil amendment, a P-loaded bamboo and eggshell composite is a promising fertilizer for long-term soil improvement. In this work, the feasibility of calcined bamboo and eggshell (BE) for P recovery and its use as fertilizer were investigated. The adsorption capacity and mechanism were examined using adsorption kinetic, isotherm, and thermodynamic analysis. The kinetic study showed that the experimental data sets were fitted best by a pseudo second-order model, indicating chemisorption. The Langmuir isotherm model estimated maximum adsorption capacities of 95.14 and 98.40 mg/g for BE 1:1 and 2:1 adsorbent. Monolayer adsorption occurred on a homogenous surface. The adsorption reaction was non-spontaneous at 298 K and exothermic for the BE 1:1 and 2:1 adsorbent, and the calculated Langmuir separation factor indicated favorable conditions for P adsorption. The desorption study showed lower P desorption capacity in water than in neutral ammonium citrate. P-loaded eggshell-modified bamboo char was an effective slow-release fertilizer for Japanese mustard spinach cultivation, which is a sustainable and environment friendly use of P-loaded materials. •Transformation of locally available biowaste into adsorbent to recover phosphate and control eutrophication.•Bamboo mixed eggshell 1:1 calcined at 800 °C had higher P adsorption capacity than calcined eggshell.•P desorption in water is low due to the strong chemical bonding between Ca of BE 1:1 and phosphate.•P-loaded BE 1:1 is effective to enhance soil fertility for long term application.