LEAD IMMOBILIZATION IN ARTIFICIAL CONTAMINATED SOIL USING SULFUR-IMPREGNATED CARBONACEOUS BAMBOO

Abstract

A novel carbonaceous immobilizing agent for heavy metal contaminated soil was prepared from
bamboo using sulfur immersion and pyrolysis, and the lead immobilization in artificial contaminated soils
using sulfur-impregnated carbonaceous material was estimated. The bamboo was powdered, dried, and then
immersed in 0.1 - 1 M K2S solution for 0 - 24 h to prepare sulfur-immersed materials. The immersed-materials
were heated at 400 oC for 1 h in nitrogen gas to produce the sulfur-impregnated carbonaceous material by
pyrolysis. The abilities of the product to immobilize lead from aqueous solution were examined to obtain the
products with high lead immobilization ability. With increasing K2S concentration, the immobilization ability
of the product for lead gradually increases and then above 0.75 M K2S those are almost constant, while 15 min
is sufficient for the immersed time to obtain the product with high lead immobilization ability. The product
prepared from material immersed in more than 0.75 M K2S solution for more than 15 min has a maximum
immobilization ability for lead ion of 2.78 mg/g. The lead immobilization using the sulfur-impregnated product
is sustainable due to the formation of leadhillite [Pb4SO4(CO3)2(OH)2] and shannonite [PbCO3‧PbO]. The
product can immobilize lead ion in various artificial lead-contaminated soils. By mixing artificial leadcontaminated soil with the sulfur-impregnated product, the eluted solution became neutral, and the eluted
concentrations of lead ion dropped below the Japanese elution standard for soil.