Sorption and Desorption of Nitrogen and Phosphorus by Zeolite and Shale
Wastewaters from animal houses contain excess of nutrients namely nitrogen (N) and phosphorus (P) apart from suspended solids and organics. Therefore, cost-effective technologies to remove N and P need to be developed. Sorption methods using the appropriate solid sorbent can be promising since this would serve as a nutrient trap which could be recycled as a nutrient source or soil mulch. Several sorbents have been investigated so far. Due to the cost effectiveness, stability and possibility of regeneration of shale and zeolites as filter media, these materials have been chosen as sorbents in the present investigation. The study focuses on the removal of N and P from wastewater using zeolite and shale and the feasibility of using the nutrient-sorbed material as slow-release fertilizers. Sorption experiments were conducted by using shale (2 mm and 2–4.7 mm) and zeolite (1 mm and 2–4 mm). Varied concentrations of N and P solutions ranging from 0 to 1000 mg L–1 were prepared from NH4Cl and KH2PO4 respectively. Results indicate that Shale 1(particle size = 2 mm) showed the highest sorption of P (170 ± 10 mg kg–1). But, the percent sorption of P was found to have a decreasing trend with increasing concentration of P in solution. Shale 2 (particle size = 2-4.7 mm) of larger particle size showed comparatively lower sorption. Both Shale 1 and 2 showed significant (R2 = 0.9566 and R2 = 0.9333) sorption of P over the P concentration in solution. Zeolites showed approximately 90% sorption of NH4, over a wider range of feed concentrations ranging from 50 to 1000 mg L–1 . The percent desorption was about 30 % of initial phosphate concentration ranging from 200 to 1000 mg L–1 when shale 1 was used as the sorbent. Shale 2 showed a percent desorption of more than 30% after 24 h desorption in deionized water. Zeolites 3 and 4 show very low desorption of less than 10%. Even though the percent sorption of NH4 in 24 h was high, the release of NH4 was slow and hence, zeolite would serve as a substrate with a property of slow ammonia release.
KeywordsNatural Zeolite Feed Concentration Sorption Efficiency Swine Wastewater Swine Farm
Southern Water Quality, Texas A&M and USDA CSREES
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