Phosphate capture from biogas slurry with magnesium-doped biochar composite derived from Lycium chinensis branch filings: performance, mechanism, and effect of coexisting ions

Simultaneous decontamination of phosphorus and bisphenol A from livestock wastewater with boehmite-modified carbon composite

In this work, a novel boehmite-modified carbon adsorbent (BMCC) derived from moldy corn was used for simultaneous removal of P and bisphenol A (BPA) from livestock wastewater. The results showed that BMCC had a high specific surface area (308.82 m2/g) with boehmite nanoparticles anchored on its surface. BMCC showed high P and BPA decontamination capabilities (40.98 mg/g for P and 54.65 mg/g for BPA by Langmuir model). The adsorbed amount of P declined as pH increased from 4 to 10, while the adsorbed amount of BPA remained steady until pH increased to 10. After 6 cycles of BMCC use, the P and BPA adsorption efficiencies reduced by 21.75 % and 19.41 %, respectively. The adsorption of P was dominated by electrostatic attraction and complexation, while the adsorption of BPA was controlled by hydrogen bonding, electrostatic interaction, and π-π association. In conclusion, BMCC is an effective treatment for decontaminating P- and BPA-contaminated livestock wastewater.

Recent developments in metallic-nanoparticles-loaded biochars synthesis and use for phosphorus recovery from aqueous solutions. A critical review

Phosphorus (P) represents a major pollutant of water resources and at the same time a vital element for human and plants. P recovery from wastewaters and its reuse is a necessity in order to compensate the current important depletion of P natural reserves. The use of biochars for P recovery from wastewaters and their subsequent valorization in agriculture, instead of synthetic industrial fertilizers, promotes circular economy and sustainability concepts. However, P retention by pristine biochars is usually low and a modification step is always required to improve their P recovery efficiency. The pre- or post-treatment of biochars with metal salts seems to be one of the most efficient approaches. This review aims to summarize and discuss the most recent developments (from 2020- up to now) in: i) the role of the feedstock nature, the metal salt type, the pyrolysis conditions, and the experimental adsorption parameters on metallic-nanoparticles-loaded biochars properties and effectiveness in recovering P from aqueous solutions, as well as the dominant involved mechanisms, ii) the effect of the eluent solutions nature on the regeneration ability of P-loaded biochars, and iii) the practical challenges facing the upscaling of P-loaded biochars production and valorization in agriculture. This review shows that the synthesized biochars through slow pyrolysis at relatively high temperatures (up to 700-800 °C) of mixed biomasses with Ca- Mg-rich materials or impregnated biomasses with specific metals in order to from layered double hydroxides (LDHs) biochars composites exhibit interesting structural, textural and surface chemistry properties allowing high P recovery efficiency. Depending on the pyrolysis's and adsorption's experimental conditions, these modified biochars may recover P through combined mechanisms including mainly electrostatic attraction, ligand exchange, surface complexation, hydrogen bonding, and precipitation. Moreover, the P-loaded biochars can be used directly in agriculture or efficiently regenerated with alkaline solutions. Finally, this review emphasizes the challenges concerning the production and use of P-loaded biochars in a context of circular economy. They concern the optimization of P recovery process from wastewater in real-time scenarios, the reduction of energy-related biochars production costs and the intensification of communication/dissemination campaigns to all the concerned actors (i.e., farmers, consumers, stakeholders, and policymakers) on the benefits of P-loaded biochars reuse. We believe that this review is beneficial for new breakthroughs on the synthesis and green application of metallic-nanoparticles-loaded biochars.

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

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.

Bio-assembled MgO-coated tea waste biochar efficiently decontaminates phosphate from water and kitchen waste fermentation liquid

Crystal morphology of metal oxides in engineered metal-biochar composites governs the removal of phosphorus (P) from aqueous solutions. Up to our best knowledge, preparation of bio-assembled MgO-coated biochar and its application for the removal of P from solutions and kitchen waste fermentation liquids have not yet been studied. Therefore, in this study, a needle-like MgO particle coated tea waste biochar composite (MTC) was prepared through a novel biological assembly and template elimination process. The produced MTC was used as an adsorbent for removing P from a synthetic solution and real kitchen waste fermentation liquid. The maximum P sorption capacities of the MTC, deduced from the Langmuir model, were 58.80 mg g−1 from the solution at pH 7 and 192.8 mg g−1 from the fermentation liquid at pH 9. The increase of ionic strength (0–0.1 mol L−1 NaNO3) reduced P removal efficiency from 98.53% to 93.01% in the synthetic solution but had no significant impact on P removal from the fermentation liquid. Precipitation of MgHPO4 and Mg(H2PO4)2 (76.5%), ligand exchange (18.0%), and electrostatic attraction (5.5%) were the potential mechanisms for P sorption from the synthetic solution, while struvite formation (57.6%) and ligand exchange (42.2%) governed the sorption of P from the kitchen waste fermentation liquid. Compared to previously reported MgO-biochar composites, MTC had a lower P sorption capacity in phosphate solution but a higher P sorption capacity in fermentation liquid. Therefore, the studied MTC could be used as an effective candidate for the removal of P from aqueous environments, and especially from the fermentation liquids. In the future, it will be necessary to systematically compare the performance of metal-biochar composites with different metal oxide crystal morphology for P removal from different types of wastewater.

Graphical Abstract

A Stable Fe-Zn Modified Sludge-Derived Biochar for Diuron Removal: Kinetics, Isotherms, Mechanism, and Practical Research

To remove typical herbicide diuron effectively, a novel sludge-derived modified biochar (SDMBC600) was prepared using sludge-derived biochar (SDBC600) as raw material and Fe-Zn as an activator and modifier in this study. The physico-chemical properties of SDMBC600 and the adsorption behavior of diuron on the SDMBC600 were studied systematically. The adsorption mechanisms as well as practical applications of SDMBC600 were also investigated and examined. The results showed that the SDMBC600 was chemically loaded with Fe-Zn and SDMBC600 had a larger specific surface area (204 m²/g) and pore volume (0.0985 cm³/g). The adsorption of diuron on SDMBC600 followed pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum diuron adsorption capacity of 17.7 mg/g. The biochar could maintain a good adsorption performance (8.88-12.9 mg/g) under wide water quality conditions, in the pH of 2-10 and with the presence of humic acid and six typical metallic ions of 0-20 mg/L. The adsorption mechanisms of SDMBC600 for diuron were found to include surface complexation, π-π binding, hydrogen bonding, as well as pore filling. Additionally, the SDMBC600 was tested to be very stable with very low Fe and Zn leaching concentration ≤0.203 mg/L in the wide pH range. In addition, the SDMBC600 could maintain a high adsorption capacity (99.6%) after four times of regeneration and therefore, SDMBC600 could have a promising application for diuron removal in water treatment.