Taguchi design-based enhancement of heavy metals bioremoval by agroindustrial waste biomass from artichoke.

Abstract

Water pollution by heavy metals is considered aworldwide environmental concern. These pollutantsare highly toxic and persistent and therefore tendto bioaccumulate in the food chain, with potentialchronic hazards to human beings and adverseimpacts to the ecosystem [1].Recently there has been increased research interestin the application of lignocellulosic agricultural byproductsto develop low-cost adsorbents for waterdetoxification to reduce environmental problems[2]. Food processing activities produce largeamounts of waste and by-products. Artichoke isan edible plant native to the Mediterranean regionproduced abundantly in Spain. The industrialprocessing of this plant generates a lot of leafylignocellulosic waste that could be efficiently andsustainably valorized.Bioremoval with low-cost sorbents is proved to bean excellent alternative technology for the treatmentof heavy metal-containing aqueous effluents [3],and agroindustrial waste biomass from artichoke isa promising sorbent that should be investigated. Inthis work, Taguchi (DOE – Design of Experiment)approach of orthogonal array experimental designwas used for multivariate optimization of thebioadsorptive recovery of Cd(II), Pb(II), Cu(II)using agroindustrial waste from artichoke assorbent.Agroindustrial waste biomass from artichokes(Cynarascolymus L.) grown in the Region ofMurcia was used. The starting material, mainlycomposed of external bracts and stems was driedat 70 ºC for 24 hours. The dry material was thenmilled and passed through a sieve of 18 mesh (1mm) to obtain the sorbent powder.Effective factors on adsorption process such aspH, sorbent dosage, initial metal concentration andtemperature were considered in each case. So, fourfactors at three levels each one were investigatedaccording to a L9 (43) experimental set for each metal.The levels of each parameter were fixed accordingto typical values reported in the bibliography [4].In each run 100 mL of metal solution at differentinitial concentration, sorbent dosages, temperaturesand pH values was shaken at fixed contact time (24hours). Afterward the supernatant was filtered andcollected for analysing metal concentration in anICP-OES system. The metal uptake capacity (qe)as, mg of metal bioremoved per gram of sorbent,was then calculated.The Langmuir, Freundlich and Temkin adsorptionisotherm models were applied to the experimentaldata. To investigate the sorption mechanism thepseudo-first order model, the pseudo-second ordermodel and the intraparticle diffusion model wereapplied at different experimental conditions.The results confirm that Taguchi methodology is asuitable tool to determine the operating variablesthat significantly influence the bioremoval capacityof heavy metals by artichoke biomass.The artichoke biomass is suited for bioremovingheavy metals from aqueous solution, showingpreference for the sequestration of Pb(II), followedof Cd(II) and Cu(II) with qmax values of 68,5; 33,3and 26,3 mg/g respectively.