The sorption and desorption of phosphate-P, ammonium-N and nitrate-N in cacao shell and corn cob biochars

Published Date

June 2013, Vol.91(11):1612–1619, doi:10.1016/j.chemosphere.2012.12.057

Title 

The sorption and desorption of phosphate-P, ammonium-N and nitrate-N in cacao shell and corn cob biochars

• Author 

• S.E. Hale ^a,,
• V. Alling ^a
• V. Martinsen ^b
• J. Mulder ^b
• G.D. Breedveld ^a,c
• G. Cornelissen ^a,b,d

• aNorwegian Geotechnical Institute (NGI), P.O. Box 3930, Ullevål Stadion, NO-0806 Oslo, Norway
• bDepartment of Plant and Environmental Sciences (IPM), Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway
• cDepartment of Geosciences, Oslo University, Oslo, Norway
• dDepartment of Applied Environmental Sciences (ITM), Stockholm University, 10691 Stockholm, Sweden

Received 17 August 2012. Revised 30 November 2012. Accepted 8 December 2012. Available online 29 January 2013.

Abstract

The sorption of PO₄–P, NH₄–N and NO₃–N to cacao shell and corn cob biochars produced at 300–350 °C was quantified. The biochars were used; (i) as received (unwashed), (ii) after rinsing with Millipore water and (iii) following leaching with Millipore water. In addition to sorption, desorption of PO₄–P from the unwashed biochars was quantified. There was no sorption of PO₄–P to either washed or rinsed biochars, but following leaching, both biochars adsorbed PO₄–P and distribution coefficients (K_d L kg⁻¹) were very similar for both materials (10^1.1±0.5 for cacao shell biochar and 10^1.0±0.2 for corn cob biochar). The BET surface area and micropore volume increased 80% and 60% for the cacao shell and corn cob biochars following leaching. After 60 d, 1483 ± 45 mg kg⁻¹ and 172 ± 1 mg kg⁻¹ PO₄–P was released from the cacao shell and corn cob biochars. NH₄–N was sorbed by both unwashed biochars, albeit weakly with K_d values around 10² L kg⁻¹. We speculate that NH₄–N could bind via an electrostatic exchange with other cationic species on the surface of the biochar. There was no significant release or sorption of NO₃–N from or to either of the biochars.

Highlights

► The adsorption of phosphate, ammonium and nitrate to cacao shell and corn cob biochars was quantified. ► Unwashed biochars released phosphate, adsorbed ammonium and had no effect on nitrate. ► Following extensive leaching both biochars adsorbed phosphate. ► The desorption of phosphate from both biochars was quantified.

Keywords

• Biochar
• Nitrate
• Phosphate
• Ammonium
• Sorption
• Desorption

---

 Table 1

Table 1.

Fig. 1.

 Table 2

Table 2.

Fig. 2.

Fig. 3.

• DOC (2.2M)

Supplementary data 1

• ⁎ 
  Corresponding author. Tel.: +47 46948357.

For further details log on website :
http://www.sciencedirect.com/science/article/pii/S0045653513000052