Immobilization of Ni and Cd in Soil by Biochar Derived From Unfertilized Dates

Effect of biochar, derived from unfertilized dates, on the immobilization of Cd and Ni, in a sandy loam alkaline soil, was investigated. The biochar was applied to the soil columns at the rate of 0.5, 1, and 2 % (w/w) artificially polluted with 10 mg kg(-1) Cd and 100 mg kg(-1) Ni. After 1 month incubation of soil-biochar mixture under ambient conditions, the soil bulk density was reduced by 0.19 g cm(-3) as compared with no biochar addition with increase in soil pH. A reduction of 53% in the NH4NO3-extractable soil Ni was recorded as compared with the corresponding control without biochar addition. After incubation, the water-soluble Ni and NH4NO3-extractable soil Cd and Ni contents were significantly lower in all the biochar treatments than the control. A reduction of 53 % in the NH4NO3-extractable soil Ni was recorded as compared with the corresponding control. The biochar content separated from the incubated soil showed low concentrations of NH4NO3-extractable Cd and Ni. The total Ni and Cd contents recovered from biochar samples after incubation were 35.2 and 3.7 mg kg(-1), respectively. Their contents in soil were substantially reduced by the incorporation of biochar amendment (114 to 57.2 mg kg(-1) Ni, 9 to 5.6 kg(-1) Cd) as compared with the no-biochar control. Therefore, addition of the biochar improved the soil physical properties and succeeded in immobilizing the studied metals.