Algal Biosorbent Research Articles

Multicomponent biosorption in fixed beds

The biosorption of Cu, Zn, Cd and Fe from multicomponent mixtures was studied in a flow-through column packed with Sargassum algal biosorbent in the Ca-form. The effects of competitive ion exchange such as the elution order of toxic metals from the column, and the concentration overshoots in column effluent were investigated both experimentally and by means of an ion exchange equilibrium column model (ECM). The ECM predicted, and the experiments confirmed, that from the feed containing Cu 2+, Zn 2+ and Cd 2+, zinc broke through the column first, followed by cadmium and copper. When the binary mixtures containing 30 mg/l of Cu 2+ and 4 mg/l of either Cd 2+ or Zn 2+ were passed through the column, the concentrations of Zn and Cd ions in the column effluent overshot the 4 mg/l feed concentration. The time interval between the overshoot of Zn and the breakthrough point of Cu was significantly longer than that between the overshoot of Cd and the breakthrough point of Cu. However, Zn did not overshoot when the feed contained 50 mg/l of Cd and 4 mg/l of Zn. The ECM successfully predicted both the occurrence and the magnitude of the overshoots. The service time of a column treating multimetal mixtures was successfully predicted by combining the ECM with a mass transfer column model (MTCM).

NMR imaging of heavy metal absorption in alginate, immobilized cells, and kombu algal biosorbents

In this contribution, an NMR imaging study of heavy metal absorption in alginate, immobilized-cell biosorbents, and kombu (Laminaria japonica) algal biomass is presented. This method provides the good possibility of directly monitoring the time evolution of the spatial distribution of the ions in the materials. From these results, we demonstrate that rare earth ions are absorbed with a steep reaction front that can be described very well with a modified shrinking core model, while copper ions are absorbed with a more diffuse front.

Interference of Aluminum in Copper Biosorption by an Algal Biosorbent

Abstract Cu and Al sorption capacities of NaOH-treated Sargassum fluitans biomass were studied using equilibrium methodology. An evaluation of sorption performance and modeling in a two-metal system was carried out using a modified multicomponent Langmuir isotherm. The maximum Cu and Al uptakes calculated from the Langmuir isotherm were 1.54 mmol/g (9.8 weight percent) and 3.75 mmol/g (10.1 weight percent) at pH 4.5, respectively. However, these values were 1.35 mmol/g for Cu and 1.58 mmol/g for Al at pH 3.5. The modified Langmuir model gave the following affinity correlated coefficients: 0.20 for Cu and 6.82 for Al at pH 4.5, and 2.90 for Cu and 3.13 for Al at pH 3.5. The interference of Al in Cu biosorptive uptake was assessed by “cutting” the three-dimensional uptake isotherm surfaces at constant second-metal final concentrations. Equimolar final equilibrium concentrations of Cu and Al of 1 mM at pH 4.5 reduced Cu and Al uptakes by 83.4 and 5.5%, respectively. However, these reductions at pH 3.5 were 53.0 (Cu) and 29.1% (Al).

Biosorption of toxic metal ions by alkali-extracted biomass of a marine cyanobacterium, Phormidium valderianum BDU 30501

Alkali-extracted biomass of Phormidium valderianum BDU 30501, a marine filamentous, non-heterocystous cyanobacterium adsorbed more than 90% of cadmium ions from solutions containing 0.1–40 mM. Cadmium binding accounted up to 18% of biomass weight (w/w). The algal biosorbent was also efficient is sequestering metal ions (Cd2+, Co2+, Cu2+, Ni2+) from a mixture. Biosorbent placed in dialysis tubing could concentrate Cd2+ (50–65%) from 1l solution (10 and 100 ppm) at equilibrium. Biosorbent immobilized in polyvinyl foam also removed cadmium and cobalt efficiently, but required longer contact times (24 h). Most of the bound metal ions (> 80%) could be desorbed with 0.1 M HCl or EDTA, while other reagents were less efficient in the order: H2SO4 > NH4Cl > CaCl2 > Na2SO 4 > KSCN > KCl > NH4OH > NaHCO3. The regenerated biosorbent retained 80% of the initial binding capacity for Cd2+ and 50% binding capacity for Co2+ up to three cycles of reuse. Infrared spectra of the biosorbent preparation suggested carboxyl groups to be the primary sites for metal binding.

NMR imaging of heavy metal absorption in alginate, immobilized cells, and kombu algal biosorbents

NMR imaging of heavy metal absorption in alginate, immobilized cells, and kombu algal biosorbents

Intraparticle Diffusivity of Cd Ions in a New Biosorbent Material

Cadmium equilibrium sorption isotherms were determined for formaldehyde crosslinked Sargassum fluitans, establishing that an effective regeneration of the new biosorbent material is possible by an acid wash. Batch desorption kinetics were investigated at pH values of 1.0 and 2.0. By incorporating the linear and non-linear Langmuir equilibrium isotherm relationships into the rate equations, a mathematical model was proposed for modeling the metal desorption process. The model was solved numerically and a MATLAB computer program was used to curve-fit the experimental data. The model successfully predicted the Cd 2+ elution concentration profile in a batch reactor. The average values of the intraparticle diffusivity of Cd 2+ in the algal biosorbent calculated from the model were 3.40 x 10 -6 and 1.65 x 10 -6 cm 2 s -1 , 0.473 and 0229 times the molecular diffusivity of Cd 2+ in water, at pH values of 1.0 and 2.0, respectively. These values agreed well with theoretical predictions.

Desorption of cadmium from algal biosorbent

AbstractDesorption of metal‐laden new biosorbent material was studied using batch and column equilibrium elution processes. Equilibrium screening tests of cadmium desorption established a solution of HC1 as the most appropriate eluant at approximately pH 1.0. The desorption of Cd by protons was indicated to be a reversible exchange with a stoichiometric coefficient of 1.24. The solid to liquid ratio (biosorbent mass to elutant volume) is described as a key parameter in determination of elution efficiency, affecting simultaneously the pH at desorption equilibrium, the concentration of cadmium released, and the concentration ratio of the overall metal recovery process. When the pH is maintained constant, the solid to liquid ratio has little influence on metal recovery but still controls the concentration ratio. Recycling a small amount of eluant through a desorption column with metal‐laden biosorbent material resulted in very high solid‐to‐liquid ratios (up to 130 g/L) leading to high value of 70 for the metal concentration ratio of the sorption/desorption process. No loss of cadmium biosorbent properties was observed in three consecutive metal uptake/desorption cycles.