Abstract:
In recent years, the removal and recovery of phosphate (PO4
3−) from freshwater
reservoirs using carbonaceous adsorbents has received much attention to address
eutrophication issues and plant phosphate requirements. The viability of FeCl3 impregnated
biochar (Fe@CBC) synthesized via co-pyrolysis of wheat straw (WS) and sewage sludge
(SS) for phosphate removal from water under systematically designed sorption experiments
and its subsequent potential as phosphatic fertilizer for improving plant growth, was
thoroughly investigated in this study. The relatively higher PO4
3− sorption performance of
Fe@CBC (5.23 mg/g) compared to FeCl3 impregnated biochars (Fe@WBC: 4.16 mg/g and
Fe@SBC: 5.14 mg/g) synthesized via separate pyrolysis of WS and SS were primarily
ascribed to the nano porous structure, higher point of zero charge (pHpzc) and enriched iron
complexes on its surface (Fe-OH and FeC). Consequently, dominant sorption mechanism of
PO4
3− ions towards Fe@WBC was associated to ligand exchange and chemisorption whereas
that of Fe@SBC and Fe@CBC was identified as electrostatic surface complexation coupled
with reduction. In comparison to Fe@WBC and Fe@SBC, the surface properties and
identified phenomenon allowed Fe@CBC to efficiently recover PO4
3− ions under optimal
water chemistry conditions and coexisting interfering species environment. Additionally,
PO4
3-
-sorbed Fe@CBC effectively improved the physical growth (root length: 2 cm, shoot
length: 9 cm, fresh weight: 79 mg and dry weight: 8.3 mg) of mustard plants. Economic
analysis suggested profit of PO4
3-
removal and recovery by Fe@CBC was $1.5 per Kg.
Therefore, PO4
3-
-sorbed Fe@CBC could be a promising phosphatic fertilizer for improving
plant growth and may have agricultural applications.
