Abstract

The presence of heavy metals, such as Pb(II), in bodies of water generates alterations in environmental quality and public health, due to their solubility and their ability to accumulate in the trophic chain. It is necessary to control the entry of these elements into the environment, the possibility of developing methods to remove this pollutant with low-cost raw materials, considered as useless waste. Within this category are the organic waste from the "El Avelino" flower market, vegetable waste such as rose stems. As an alternative for the elimination of heavy metals and the use of these vegetable wastes, the adsorption capacity and removal efficiency of Pb(II) in simulated solution was evaluated using rose stems as biosorbent. Chemical activation of the rose stem biomass was performed with an acid hydrolysis process followed by an alkaline hydrolysis (TRHS). Batch tests were carried out to analyze the effect of pH on adsorption, adsorbate and adsorbent concentration and contact time to reach equilibrium, as well as to investigate the adsorption mechanism, for which adsorption isotherms and Pb(II) adsorption kinetics were studied. The results obtained showed that the adsorption of Pb(II) was pH dependent with the optimum pH being 4. The experimental equilibrium data agreed with the Langmuir isotherm model, with R2 = 0.9854, achieving a maximum adsorption capacity (Qmax) of 344.8276 mg Pb(II)/g of rose stem, with 0.05 g of biomass and a contact time of 60 min. Likewise, regarding kinetics, the biosorption data were fitted to the pseudo-second order Ho model, with a correlation coefficient of R2 = 0.9960, which best describes the adsorption process. In all tests, Pb(II) removals above 97% were achieved. To study in detail the biomass-metal interaction, Fourier Transform Infrared Spectroscopy (FTIR) was used, confirming that the rose stem biomass (TRHS) is able to interact with Pb(II) at the surface level through physicochemical interactions.