Waste biomass from marine environment as arsenic and lead biosorbent

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1 Advanced Materials Research Vols (2009) pp online at (2009) Trans Tech Publications, Switzerland Online available since 2009/May/19 Waste biomass from marine environment as arsenic and lead biosorbent F. Beolchini 1,a, C. Pennesi 1,b, B. Testaferri 1, C. Totti 1, I. De Michelis 2 and F. Vegliò 2,c 1 Polytechnic University of Marche, Department of Marine Sciences, Via Brecce Bianche, Ancona, Italy 2 University of L Aquila, Department of Chemistry, Chemical Engineering and Materials, Monteluco di Roio, L Aquila, Italy a f.beolchini@univpm.it, b c.pennesi@univpm.it, c francesco.veglio@univaq.it Keywords: biosorption, lead, arsenic, seaweeds, seagrasses. Abstract. This paper deals with arsenic and lead biosorption by different waste biomasses coming from the marine environment. Shoreline seaweeds and seagrasses were used to adsorb metals from aqueous solutions, under different ph. Experimental tests were performed in order to study the equilibrium of biosorption with suspended biomass. The obtained results confirmed the possibility of using marine macrophyte biomass for heavy metal biosorption and evidenced a strong dependence of lead and arsenic uptake on the macrophyte structure. Brown algae were found to be the best sorbents for lead with a maximum observed lead uptake of 140 mg/g; green algae showed a maximum lead uptake in the range mg/g; red algae were the worst lead sorbent, in the investigated experimental conditions, with a maximum lead uptake in the range mg/g. As concerns arsenic, the macrophytes had in general good sorption abilities when compared with those of activated carbon. Furthermore red algae, that for lead were not effective, resulted to be the best sorbents for arsenic. This was explained by a different speciation in aqueous solution of lead (II), that is cationic with respect to arsenic(v), that is anionic. Introduction Biosorption of heavy metals is an alternative technology to treat industrial reflues, using as adsorbent wastes coming from agricultural and industrial activities, marine macrophytes and specially propagated biomasses of bacteria, yeast and fungi [1]. Physico-chemical mechanisms involved in metal removal can be many (physical adsorption, ion exchange, complexation and surface micro-precipitation) and simultaneously occurring in the system [2]. Of the many types of biosorbents, algal biomass has proven to be highly effective in the removal of heavy metals from aqueous solution, due to its basic biochemical constitution [3]. Furthermore the abundant availability of such biomass makes its use as metal biosorbent material very interesting [4]. The aim of the present work was the study of lead and arsenic biosorption equilibrium by different species of marine macrophytes in order to evidence any morphology effect on the macrophytes biosorption abilities. Materials and Methods Marine macrophytes. The employed biosorbent materials were obtained from several species of marine seaweeds and seagrasses. Brown algae: Cystoseira compressa Gerloff & Nizamuddin, Dyctiopteris polypodioides J.V. Lamouroux, Eisenia bicyclis Setchell, Scytosiphon lomentaria (Lyngbye) Link. Green algae: Ulva compressa Linnaeus, Ulva rigida C. Agardh, Caulerpa racemosa J. Agardh. Red algae Gracilaria bursa-pastoris (S.G. Gmelin) P.C. Silva, Porphyra leucosticta Thuret, Porphyra tenera Kjellman, Ceramium ciliatum Ducluzeau, Polysiphonia sp. Seagrasses: Cymodocea nodosa, Zostera marina Linnaeus.. Macrophyte specimens were all collected in Portonovo (Conero Natural Park, Adriatic Sea, Italy) Seagrasses samples were All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, (ID: /05/09,15:27:00)

2 598 Biohydrometallurgy 2009 collected from the beaches of Palombina, Portonovo, Passetto, Gabicce (Marche region coast, Italy, Adriatic Sea) and Torre Guaceto (Puglia region coast, Italy, Adriatic Sea). After collection, samples were washed with distilled water and dried at room temperature for 3-4 days (until a stable weight was observed). Before biosorption tests, each dried biomass was reduced in small fragments (of about 4 mm). Biosorption tests. 0.5 g of dried biomass were put in 100 ml of distilled water (biomass concentration 5 g/l) for half an hour; then a concentrated solution of PbSO 4 / As 2 O 5 was added according to experimental conditions. Aliquot amounts of solution were then periodically sampled for lead/arsenic concentration determination. The sorption isotherms at constant ph were determined according the S.A.M (Subsequent Addition Method) [5], in order to save time and reagents, after preliminary batch tests aimed at the validation of this procedure. The suspension ph was adjusted by HCl 0.1 N and controlled during the whole biosorption test. Analytical determinations. Lead and arsenic concentration in the liquid phase were determined by atomic absorption spectrophotometer (Varian Spectra 2000). All samples were diluted with HNO3 at ph 2 and stored at 4 C before the analysis. Most of the biosorption tests were replicated twice and the c.v. values ranged from 2 to 5 %. Results and Discussion Lead biosorption. A first investigation was aimed at the study of macrophyte structure effect on lead biosorption equilibrium. In particular, seaweeds of different species were tested as lead biosorbents. Figure 1 shows equilibrium isotherms (lead solid concentration, q, vs. lead liquid concentration at equilibrium, Ceq) as determined from experimental data at ph 5 and room temperature. Experimental values (points) were determined by a material balance while calculated values (lines) were given by Langmuir equation [6] where parameters q max and b, estimated by non linear regression, are reported in Table 1 for each seaweed. The analysis of reported data suggests the following remarks: - red algae are the worst lead sorbents. In fact, maximum lead uptake were lower than 15 mg/g both in the case of Porphyra and Polysiphonia specimens, and around 30 mg/g for Gracilaria biosorbent. This bad sorption abilities might be related to the simple structure of the thallus [7]; - the two green algae species showed a similar behaviour, with a maximum uptake of about mg/g for both Ulva species. Considering that these macroalgae can be infesting especially in closed zones, this significant metal sorbing ability makes biosorption a potential alternative for valorisation of such biomasses; - brown algae (both Cystoseira and Scitosyphon) appear to be very promising metal sorbents. In fact maximum lead uptake of about 140 mg/g was observed in the investigated experimental conditions. This ability can be attributed to the biochemical constitution of cell wall constituents, such as alginate and fucoidan [3]. MARINE MACROPHYTE q max (mg/g) b(l/mg) brown algae Cystoseira Scytosiphon green algae U.rigida U.compressa red algae Gracilaria Porphyra Polysiphonia Table 1. Langmuir model parameters (ph 5, biomass 5 g/l, standard errors 3-4%)

3 q (mg/g) q (mg/g) Advanced Materials Research Vols brown algae GRACILARIA PORPHYRA POLYSIPHONIA U.COMPRESSA U. RIGIDA SCITOSYPHON CYSTOSEIRA green algae 20 red algae Ceq (mg/l) Figure 1. Langmuir equilibrium isotherms for lead uptake (ph 5, room temperature, biomass 5 g/l) Arsenic biosorption. The aim of this part of the work was to assess macrophytes sorption abilities with arsenic (V). In this case it was hypothesized that different trends would be observed with respect to lead biosorption, due to different speciation of arsenic in aqueous solution: in fact, it is well known that lead is present in a cationic form and arsenic in an anionic form, according to ph [8]. Figure 2 shows arsenic specific uptake observed for different species of macrophytes with an arsenic initial concentration of 100 g/l. The adsorption of As(V) did not exceed in any case 2 mg/g This value is not comparable with lead specific uptake, due to a initial arsenic concentration significantly lower than lead. A comparison with available data in the literature under experimental conditions similar to those adopted in this work, evidenced that the tested macrophytes had good sorption capacity and comparable with those of activated carbon and other low-cost adsorbents [9]. In this case, the red seaweeds Ceramium ciliatum and Gracilaria bursa pastoris were the best sorbents (see Fig. 2). This might be attributed to cationic sites as amine groups present on the wall of seaweeds. Also Hashim and Chu [10], observing the lower adsorption capacities of red seaweeds compared with brown and green seaweeds for metals in a cationic form, as lead, supposed the presence of cationic sites on the wall of red algae: this may be attributed to the proteic cuticles present on the external surface of the red seaweeds [11]. Moreover, in the red seaweeds methyl groups of carrageenins lower the negative charge on cell wall therefore the repulsive action to anions, as arsenate ions, is less significant than in Phaeophyta and Chlorophyta. 2,0 1,8 1,6 1,4 1,2 1,0 0,8 0,6 0,4 0,2 0,0 ph 6 ph 7 ph 8 red algae brown algae green algae seagrass Ceramium Gracilaria Ulva Caulerpa Dictyopteris Cystoseira Zostera Figure 2. Arsenic specific uptake (initial arsenic concentration 100 g/l, room temperature, biomass 5 g/l)

4 600 Biohydrometallurgy 2009 Conclusions The obtained results confirmed the possibility of using marine macrophyte biomass for heavy metal biosorption and evidenced a strong dependence of lead and arsenic uptake on the macrophyte structure. In fact, brown algae and seagrasses, known to have a more complex structure than green and red algae, were found to be the best sorbents for lead and also showed good sorption abilities for arsenic. On the other hand, red algae, which have a relatively simple structure of the thallus and were the worst lead sorbents, resulted to be the best arsenic sorbents, in the investigated experimental conditions. Acnowledgements Authors are grateful to Mr. Marcello Centofanti, for his precious help in the experimental determinations. This work has been funded by Italian Ministry of Research (PRIN projects). References [1] B. Volesky: Process Metallurgy Vol. 11B (2001), p. 69. [2] F. Veglio and F. Beolchini: Hydrometallurgy Vol. 44 (1997), p [3] T.A. Davis, B. Volesky and A. Mucci: Water research Vol. 37 (2003), p [4] S. Schiewer and M.H. Wong: Chemosphere Vol. 41 (2000), p.271. [5] F. Beolchini, F. Pagnanelli, A. Reverberi and F. Vegliò: Ind. & Eng. Chem. Res. Vol.42/20 (2003), p [6] Langmuir: J. Am. Chem. Soc. Vol. 40 (1918), p [7] C. Van Den Hoek, D.G. Mann and H.M. Jahns: Algae. An introduction to phycology. Cambridge University Press, [8] F. Beolchini, F. Pagnanelli, I. De Michelis and F. Vegliò: Env. Sci. Technol. Vol. 40/8 (2006), p [9] D. Mohan and C.U. Pitmann Jr. Journal of Hazardons Materials Vol. 142 (2007), p.1. [10] M.A. Hashim and K.H. Chu: Chemical Engineering Journal Vol. 97 (2004), p [11] L.E.Graham and L.W.Wilcox: Algae. (Prentice-Hall, Englewood Cliffs, NJ 2000).

5 Advanced Materials Research Vols Biohydrometallurgy 2009 doi: / Waste Biomass from Marine Environment as Arsenic and Lead Biosorbent doi: / References [1] B. Volesky: Process Metallurgy Vol. 11B (2001), p. 69. [2] F. Veglio and F. Beolchini: Hydrometallurgy Vol. 44 (1997), p doi: /s x(96)00059-x [3] T.A. Davis, B. Volesky and A. Mucci: Water research Vol. 37 (2003), p doi: /s (03) PMid: [4] S. Schiewer and M.H. Wong: Chemosphere Vol. 41 (2000), p.271. doi: /s (99)00421-x PMid: [5] F. Beolchini, F. Pagnanelli, A. Reverberi and F. Vegliò: Ind. & Eng. Chem. Res. Vol.42/20 (2003), p doi: /ie020829h [6] Langmuir: J. Am. Chem. Soc. Vol. 40 (1918), p doi: /ja02242a004 [7] C. Van Den Hoek, D.G. Mann and H.M. Jahns: Algae. An introduction to phycology. Cambridge University Press, [8] F. Beolchini, F. Pagnanelli, I. De Michelis and F. Vegliò: Env. Sci. Technol. Vol. 40/8 (2006), p doi: /es052114m [9] D. Mohan and C.U. Pitmann Jr. Journal of Hazardons Materials Vol. 142 (2007), p.1. doi: /j.jhazmat PMid: [10] M.A. Hashim and K.H. Chu: Chemical Engineering Journal Vol. 97 (2004), p doi: /s (03)00216-x [11] L.E.Graham and L.W.Wilcox: Algae. (Prentice-Hall, Englewood Cliffs, NJ 2000).

Technical Note Modelling of equilibrium heavy metal biosorption data at different ph: a possible methodological approach

Technical Note Modelling of equilibrium heavy metal biosorption data at different ph: a possible methodological approach The European Journal of Mineral Processing and Environmental Protection Technical Note Modelling of uilibrium heavy metal biosorption data at different ph: a possible methodological approach F. Vegliò*