Continuous biosorption of Pb/Cu and Pb/Cd in fixed-bed column using algae Gelidium and granulated agar extraction algal waste

Copper biosorption by Bacillus pumilus OQ931870 and Bacillus subtilis OQ931871 isolated from Wadi Nakheil, Red Sea, Egypt

BACKGROUND

Despite being necessary, copper is a toxic heavy metal that, at high concentrations, harms the life system. The parameters that affect the bioreduction and biosorption of copper are highly copper-resistant bacteria.

RESULTS

In this work, the ability of the bacterial biomass, isolated from black shale, Wadi Nakheil, Red Sea, Egypt, for Cu2+ attachment, was investigated. Two Cu2+ resistance Bacillus species were isolated; Bacillus pumilus OQ931870 and Bacillus subtilis OQ931871. The most tolerant bacterial isolate to Cu2+ was B. pumilus. Different factors on Cu2+ biosorption were analyzed to estimate the maximum conditions for Cu biosorption. The qmax for Cu2+ by B. pumilus and B. subtilis determined from the Langmuir adsorption isotherm was 11.876 and 19.88 mg. g-1, respectively. According to r2, the biosorption equilibrium isotherms close-fitting with Langmuir and Freundlich model isotherm. Temkin isotherm fitted better to the equilibrium data of B. pumilus and B. subtilis adsorption. Additionally, the Dubinin-Radushkevich (D-R) isotherm suggested that adsorption mechanism of Cu2+ is predominately physisorption.

CONCLUSION

Therefore, the present work indicated that the biomass of two bacterial strains is an effective adsorbent for Cu2+ removal from aqueous solutions.

Removal of copper and/or zinc ions from synthetic solutions by immobilized, non-viable bacterial biomass: Batch and fixed-bed column lab-scale study

A biosorbent composed of non-viable Pseudomonas putida trapped in agar beads was able to remove Cu²⁺ and Zn²⁺ from solutions containing one or both metals. The process in batch followed pseudo second-order kinetics, with adsorption capacities of 0.255 mg Cu²⁺/g and 0.170 mg Zn²⁺/g according to the Langmuir isotherm. These values were up to ten times lower for beads without biomass. The metals became bound to OH, CH₂, CO, COC and COP groups, with the last three being provided by the biomass, which highlights its importance. Adsorption values for single-metal solutions filtered in a fixed-bed column were 0.152 mg Cu²⁺/g and 0.117 mg Zn²⁺/g, but decreased to 0.075 and 0.058, respectively, with mixed-metal solutions (1:1 ratio). In 10:1-ratio solutions, the metal in greater proportion was better adsorbed. Under all conditions, removal percentage was ∼60 %. The column could be reused throughout ten absorption/desorption cycles without significant alterations in adsorption capacity.

Continuous dye adsorption and desorption on an invasive macrophyte (Salvinia minima)

The continuous adsorption-desorption of methylene blue (MB) on an invasive macrophyte, Salvinia minima, was investigated in fixed-bed columns. The effects of bed depth (h) (9.30, 18.70, and 28 cm), inlet dye concentration (C₀) (51 ± 1.20, 154 ± 2.00, and 250 ± 1.50 mg L^-1), and flow rate (Q) (7 and 14 mL min^-1) on dye removal and breakthrough curves were assessed. Thomas, modified dose-response (MDR) and bed depth service time (BDST) models were fitted to the experimental data. Desorption and regeneration studies were also performed. The breakthrough time was affected by h, C₀, and Q. The dynamic bed capacity at the breakthrough point (q_b) increased with increasing h but decreased with increasing C₀ and Q. Dynamic bed capacities (q_e) from 318 to 322 mg g^-1 were achieved at h = 28 cm, C₀ = 154 ± 2.0, or 250 ± 1.50 mg L^-1, independently of the Q value. High MB removals were also observed (75-78%). FTIR analysis revealed that hydroxyl and carboxyl groups could be involved in dye adsorption. MDR and BDST models were both successfully used to predict the breakthrough curves of MB adsorption onto S. minima. A high regeneration efficiency (> 87%) was obtained after three adsorption-desorption cycles. These results confirm that the use of S. minima biomass could be a very efficient and eco-friendly alternative for MB adsorption in continuous mode.

A Mass Transfer Analysis of Competitive Binding of Pb, Cd, and Zn from Binary Systems onto a Fixed Zeolite Bed

The low-cost natural zeolite clinoptilolite was successfully applied for the competitive removal of Pb, Cd, and Zn from binary (Pb + Zn) and (Cd + Zn) aqueous solutions at different Pb/Zn and Cd/Zn concentration ratios. The obtained efficiency was in the range of 79.0⁻85.0%, and was similar for both systems, indicating that no loss in capacity was observed for six successive sorption-desorption cycles. In both systems, after the breakthrough, competition between the ions occurs, leading to overshooting in the Zn's initial concentration, indicating displacement of already-bound Zn with Pb and Cd from the feeding solutions. The Zn exceeded its initial concentration up to 2.3 times in the presence of Pb, and up to 1.2 times in the presence of Cd. The film diffusion was pronounced as the slowest step responsible for the overall process rate. The overall mass transfer coefficient (K_a) shows higher values for the (Cd + Zn) system compared to the (Pb + Zn) one due to reduced competition and ions migration. An SEM-EDS analysis confirmed a higher amount of bound Pb and Cd compared to Zn, and a mapping analysis revealed the equal distribution of all ions onto the zeolite surface.

Brown marine macroalgae as natural cation exchangers for toxic metal removal from industrial wastewaters: A review

The discharge of inadequately treated or untreated industrial wastewaters has greatly contributed to the release of contaminants into the environment, including toxic metals. Toxic metals are persistent and bioaccumulative, being their removal from wastewaters prior to release into water bodies of great concern. Literature reports the use of brown marine macroalgae for toxic metals removal from aqueous solutions as an economic and eco-friendly technique, even when applied to diluted solutions. Minor attention has been given to the application of this technique in the treatment of real wastewaters, which present a complex composition that can compromise the biosorption performance. Therefore, the main goal of this comprehensive review is to critically outline studies that: (i) applied brown marine macroalgae as natural cation exchanger for toxic metals removal from real and complex matrices; (ii) optimised the biosorption process in a fixed-bed column, which was further scaled-up to pilot plants. An overview of toxic metals sources, chemistry and toxicity, which are relevant aspects to understand and develop treatment techniques, is initially presented. The problem of water resources pollution by toxic metals and more specifically the participation of metal finishing industries in the environmental contamination are issues also covered. The current and potential decontamination methods are presented including a discussion of their advantages and drawbacks. The literature on biosorption was reviewed in detail, considering especially the ion exchange properties of cell wall constituents, such as alginate and fucoidan, and their role in metal sequestration. Besides that, a detailed description of biosorption process design, especially in continuous mode, and the application of mechanistic models is addressed.

Packed-bed column biosorption of chromium(VI) and nickel(II) onto Fenton modified Hydrilla verticillata dried biomass

The present study represents the first attempt to investigate the biosorption potential of Fenton modified Hydrilla verticillata dried biomass (FMB) in removing chromium(VI) and nickel(II) ions from wastewater using up-flow packed-bed column reactor. Effects of different packed-bed column parameters such as bed height, flow rate, influent metal ion concentration and particle size were examined. The outcome of the column experiments illustrated that highest bed height (25cm); lowest flow rate (10mLmin(-1)), lowest influent metal concentration (5mgL(-1)) and smallest particle size range (0.25-0.50mm) are favourable for biosorption. The maximum biosorption capacity of FMB for chromium(VI) and nickel(II) removal were estimated to be 89.32 and 87.18mgg(-1) respectively. The breakthrough curves were analyzed using Bed Depth Service Time (BDST) and Thomas models. The experimental results obtained agree to both the models. Column regeneration experiments were also carried out using 0.1M HNO3. Results revealed good reusability of FMB during ten cycles of sorption and desorption. Performance of FMB-packed column in treating secondary effluent was also tested under identical experimental conditions. Results demonstrated significant reduction in chromium(VI) and nickel(II) ions concentration after the biosorption process.

Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn

Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10mM solutions of two metals or a 5mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence Pb<Cd<Cu<Zn<Ni for the lowest metal doses, and Pb<Cu<Zn<Cd<Ni for the highest ones. The bi-metal batch experiments indicated that Cu and Pb suffered the highest retention, with high capacity to displace Cd, Ni and Zn from adsorption sites on pine bark. The transport experiments produced comparable results to those obtained in the batch experiments, with pine bark retention capacity following the sequence Pb>Cu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste.

Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column

Sorption of Pb(II) was studied by using a biosorbent mixture of algae waste biomass and Purolite A-100 resin in a packed-bed column. Mixing these two components was done to prevent the clogging of the column and to ensure adequate flow rates. Increasing of solution flow rate and initial Pb(II) concentration make that the breakthrough and saturation points to be attained earlier. The experimental breakthrough curves were modeled using Bohart-Adams, Thomas and Yoon-Nelson models, and the parameters for all these models were calculated. A regeneration efficiency of 98% was achieved using 0.1 mol L(-1) HCl and not significant changes in lead uptake capacity after three biosorption/desorption cycles were noted. The biosorbent mixture was able to remove Pb(II) from synthetic wastewater at pH 5.0 and flow rate of 3.5 mL min(-1), and the obtained effluent has better quality characteristics. The biosorbent mixture it is suitable for a continuous system for large-scale applications.