Cadmium removal from wastewater by sponge iron sphere prepared by hydrogen reduction

A new type of sponge iron sphere (NSIS) with 1-5 mm diameter, made of concentrated iron powder and possessed high activity and intension, was prepared by mini-pellet sintering integrated with H₂ direct reduction. Static state experiment has been carried on to investigate the Cd²⁺ removal efficiency from wastewater by the NSIS and to explore the Cd²⁺ removal reaction kinetics. It was suggested that initial pH value and Cd²⁺ original concentration had significant influence on Cd²⁺ removal percentage. Cd²⁺ removal percentage decreased significantly with the increasing of Cd²⁺original concentration whether the original pH value be adjusted to 3.0 or without adjustment. The results showed that the Cd²⁺ removal process followed the first order reaction because the reaction order was from 0.803 to 0.996. The apparent reaction rate constant between Cd²⁺ and NSIS was from 0.0025 to 0.1000 (mg·L^?1)^1-n·min^?1. Compared with SIS reduced by charcoal reduction, NSIS deoxided by hydrogen possessed higher activity, and could remove the same quantity of Cd²⁺ within a shorter period of time.