Heavy Metal Contaminated Agricultural Soil Treatment by Spent Coffee Grounds (SCG)

Heavy metal contamination issues are becoming increasingly common in Iran and elsewhere, the exposure of human to heavy metals can occur through a variety of routes, which include inhalation as dust or fume, vaporization and ingestion through food and drink. On the other hand, the increase of agricultural and food wastes and their accumulation in the environment causes pollution. Studies show that these wastes are capable of adsorbing heavy metals and we can use them as bio-degraders to remove heavy metals from the soil. Recent studies showed that Spend Coffee Ground (SCG) have the potential of adsorption of heavy metals. SCG as a one of the most common waste materials was chosen for detoxification of contaminated soil in order to bio-adsorbing Nickel and Cadmium from soil as well as cultivated edible vegetable Coriandrum sativum (Coriander). Packed potting soil purchased from recognized centers from Tehran market and 45 same vases in the same situation such as light, water, soil, temperature and other conditions were prepared. Pharmaceutical Effluents from Nutrition and food sciences Research Center were added in the first day of study by specified physicochemical composition such as COD, BOD and mineral and toxic metal contents. The coriander was being planted directly on the same vases. Meanwhile in 40 vases the SCG (from 0% to 5%) dry weight percentage were mixed by soil, due to observing the effect of SCG as adsorbent and in defined times: 0, 10, 20, 30, 40 days in the study. The Cadmium and Nickel contents in aerial parts of vegetable in treated and untreated samples were determined by ICP-QES. Ion concentration were addressed in three replicates. The soil, leaves of vegetable were digested by wet method according the standard protocol. Mean values were calculated using Analysis of Variance, (ANOVA). Results revealed that SCG has more potential to adsorb Cadmium during first days of study (p<0.001) and adsorption capacity varied by considering the effects of assorted parameters like contact time, initial concentrations, pH, and adsorbent dose. SCG can accumulate high level of Cadmium after 30 days (p<0.05) while the results revealed that the significant Nickel removing, was observed after 40 days. Authors recommend to utilize other food and agricultural wastes for future studies as well as other contaminated vegetables. In conclusion, SCG could be a good adsorbent to remove heavy metals from soil amendments and improve the safety of vegetable and soil in the same time.

Keywords:

Detoxification , Heavy metals , contaminated vegetable , Spent coffee ground