Alginate Fiber For Heavy Metal Ions Adsorption Properties

Seaweed is one of the richest marine resources in China. The output of alginate occupies the first in the world. There are abundant of carboxyl and hydroxyl groups in alginates, which had strong complication ability with the metal ions, through complication with ion exchange and metal ions to form stable cheaters. Alginic acid fiber is prepared by sodium alginate through wet spinning. Alginic acid fiber is one of the effective adsorbents because of its high adsorptive capacity, easy handling, low-cost, rapid adsorption and simple recycling. It can adsorb heavy metals rapidly and attain good purification effect. When adsorption reached equilibrium or adsorption ability weakened, alginic acid fiber can be regenerated with immerging a few minutes in HCl aqueous solution. Alginic acid fiber is a green ideal adsorption material.In this paper, we selected alginic acid fiber as biosorbent, to remove Pb2+ and Fe3+ from solutions by batch operation. At the same time, fixed bed column is adopted to remove Pb2+ and Cu2+ from solutions.The properties of alginate acid fiber as an adsorbent for removing copper and lead ions from synthetic solutions were investigated in a batch system. The influential factors, such as adsorbents dose, pH values, initial concentration, contact time and temperature etc. were studied. The mechanism, thermodynamics and kinetics of adsorptive process were investigated also. The batch experiments show that in a very short time, alginic acid fiber reached adsorption equilibrium, and desorption did not significantly enhance, indicating Pb2+ and Fe3+ was strongly adsorbed. The fittest pH for Pb2+ adsorption is 5.5, and for Fe3+ is 2.0. With the initial ion concentration increasing, adsorption capacity of alginate acid fiber increases. The uptake of metal ions was found to decrease with increasing temperature, and Fe3+ is more affected. The adsorption can reach best when alginate acid fiber dosage is 4g/L. As a result of the kinetic studies, it was observed that the adsorption data conforms to the pseudo-second-order Elovich equation and intraparticle diffusion models, chemisorptions rather than physisorption is the main reaction step throughout the adsorption process. Adsorption behavior of Fe3+ can be approximately described with the Langmuir and Freundlich equations in the studies of static adsorption while Pb2+ can be described with Freundlich equations.△G0 is negative indicating that adsorption of Pb2+ on alginic acid fiber is spontaneous. The negative values of AH0 confirm the exothermic nature of adsorption. The negative values of△S0 suggest the decreased randomness at the solid-solute interface during biosorption.The adsorptions of Pb2+ and Cu2+ onto alginate acid fiber in aqueous solution were also studied with fixed-bed column. The practical application shows that the properties of alginate acid fiber are excellent. In the given experimental conditions, experimental results can be well fitted with Thomas equation and Yoon-Nelson equation. The regeneration and subsequent use of alginate acid fiber shows that the adsorption process can be applied with column. It is clear that alginate acid fiber is a good adsorbents for Pb2+ and Cu2+ and have great potential for the removal of heavy metal ions from aqueous systems.