Recovery of phosphate from aqueous solution by magnesium oxide decorated magnetic biochar and its potential as phosphate-based fertilizer substitute (original) (raw)

Iron and Magnesium Impregnation of Avocado Seed Biochar for Aqueous Phosphate Removal

Clean Technologies

There has been increasing interest in using biochar for nutrient removal from water, and its application for anionic nutrient removal such as in phosphate (PO43−) necessitates surface modifications of raw biochar. This study produced avocado seed biochar (AB), impregnated Fe- or Mg-(hydr)oxide onto biochar (post-pyrolysis), and tested their performance for aqueous phosphate removal. The Fe- or Mg-loaded biochar was prepared in either high (1:8 of biochar to metal salt in terms of mass ratio) or low (1:2) loading rates via the co-precipitation method. A total of 5 biochar materials (unmodified AB, AB + High Fe, AB + Low Fe, AB + High Mg, and AB + Low Mg) were characterized according to their selected physicochemical properties, and their phosphate adsorption performance was tested through pH effect and adsorption isotherm experiments. Fe-loaded AB contained Fe3O4, while Mg-loaded AB contained Mg(OH)2. The metal (hydr)oxide inclusion was higher in Fe-loaded AB. Mg-loaded AB showed a u...

Synthesis and phosphate adsorption performance of elephant dung biochar modified with magnesium and iron

Journal of Metals, Materials and Minerals, 2022

The large production volume combined with the high lignocellulose content makes elephant dung an attractive and underutilized biomass resource, but also presents waste management problems for elephant orphanages. This study explored the conversion of elephant dung into biochars by slow pyrolysis at 500°C for the recovery of phosphate. The unmodified biochar (BC500) had a specific surface area (SBET) of 62.5 m2×g-1 with point of zero charge (pHPZC) of 7.7. Biochar modification with MgCl2 (MgBC500) and FeCl3 (FeBC500) by pre-pyrolysis treatment affected the SBET (48.7 m2×g-1 and 259.4 m2×g-1, respectively) and pHPZC (8.7 and 3.3, respectively). In FeBC500, Fe was present as magnetite (Fe3O4) and hematite (α-Fe2O3) as confirmed by X-ray diffraction. Instead of adsorption, both BC500 and MgBC500 released phosphate at pH 3-6. Phosphate adsorption onto FeBC500 reached equilibrium within 24 h and followed pseudo-second order kinetics. The adsorption isotherm was best described with the Lan...

Mg/Zr modified nanobiochar from spent coffee grounds for phosphate recovery and its application as a phosphorous release fertilizer

Environmental Nanotechnology, Monitoring & Management, 2023

Excessive phosphorous discharge causes eutrophication of the aquatic system. Hence, from the viewpoints of eutrophication control and sustainable use of phosphorous, its recovery from wastewater is essential. Herein, Mg/Zr modified nanobiochar from spent coffee grounds (Mg/Zr/CNBC) is reported as an efficient adsorbent for phosphate recovery, and phosphorous release fertilizer. SEM, XRD, and FTIR characterizations of the adsorbent before and after adsorption suggested that phosphate is involved in both physisorption and chemisorption. Adsorption of phosphate on Mg/Zr/CNBC and factors affecting the process viz pH, contact time, initial phosphate concentrations, and dose of adsorbent were investigated in batch mode experiments. Mg/Zr/CNBC showed a 23.36 and 11.84 % improvement in the adsorption efficiency than the pristine and Mg-modified nanobiochar respectively. Acidic conditions favored the adsorption of phosphate on Mg/Zr/CNBC with maximum adsorption (98.5 %) at pH 1. Adsorption of phosphate followed pseudo-second-order kinetics. The corresponding equilibrium constant (K 2) and adsorption capacity were calculated to be 0.316 g/mg. min and 39.4 mg/g respectively. The equilibrium data obtained at different phosphate concentrations better fitted the Freundlich adsorption isotherm model (R 2 = 0.998) suggesting multilayer adsorption of phosphate on a heterogeneous surface. Further, the utility of phosphate-laden Mg/Zr/CNBC as a phosphorous-release fertilizer was demonstrated in a pot test. Results of the pot test showed that phosphate-laden Mg/Zr/CNBC improved the growth of Wheat and Chickpeas by 31.16 and 29.63 % respectively. The result highlights a circular economy approach for spent coffee grounds.

Effect of corn pre-puffing on the efficiency of MgO-engineered biochar for phosphorus recovery from livestock wastewater: mechanistic investigations and cost benefit analyses

Biochar

To improve the phosphorus (P) recovery efficiency from livestock wastewater, a novel MgO doped mildewed corn biochar with thermal pre-puffing treatment (Mg-PBC) and without pre-puffing (Mg-BC) was synthesized and tested. The thermal-puffing pretreatment improved the effectiveness of metal soaking and MgO dispersion. P recovery time with Mg-PBC (7 h) was significantly shorter than that with Mg-BC (12 h). Moreover, Mg-PBC showed significantly higher P recovery capacity (241 mg g−1) than Mg-BC (96.6 mg g−1). P recovery capacity of the Mg-PBC fitted to the Thomas model was 90.7 mg g−1, which was 4 times higher than that of Mg-BC (22.9 mg g−1) under column test conditions. The mechanisms involved in P recovery included precipitation, surface complexation, and electrostatic interaction. After adsorption, both Mg-BC and Mg-PBC showed relatively low regeneration abilities. The P loaded Mg-BC (Mg-BC-P) and Mg-PBC (Mg-PBC-P), the later particularly, obviously increased the available P content...

Enhancing phosphate adsorption by Mg/Al layered double hydroxide functionalized biochar with different Mg/Al ratios

The Science of the total environment, 2016

Mg/Al ratio plays a significant role for anion adsorption by Mg/Al-layered double hydroxides (Mg/Al-LDHs) modified biochar. In this study, Mg/Al-LDHs biochar with different Mg/Al ratios (2, 3, 4) were prepared by co-precipitation for phosphate removal from aqueous solution. Factors on phosphate adsorption including Mg/Al ratio, pH, and the presence of other inorganic anions were investigated through batch experiments. Increasing Mg/Al ratio in the Mg/Al-LDHs biochar composites generally enhanced phosphate adsorption with Langmuir adsorption maximum calculated at 81.83mg phosphorous (P) per gram of 4:1Mg/Al-LDHs biochar at pH3.0. The adsorption process was best described by the pseudo-second-order kinetic model. Solution pH had greater effects on the phosphate adsorption by Mg/Al LDHs biochar composites with lower Mg/Al ratios. The presence of other inorganic anions decreased the phosphate adsorption efficiency in the order of F(-) > SO4(2-) > NO2(-) >Cl(-). Phosphate adsorp...