# Efficient Sulfate Adsorption on Modified Adsorbents Prepared from _Zea mays_ Stems
###### Abstract  
The effect of temperature on the sulfate adsorption capacity of adsorbents prepared from corn stalks (_Zea mays_) was evaluated. Two bioadsorbents were prepared from biomass: a biochar modified with H2 SO4 with mass: volume ratio 1:1 (B 1:1), and cellulose modified with cetyl trimethyl ammonium chloride (CTAC). There were also determined thermodynamic parameters (\(\Delta\)G\({}^{\circ}\), \(\Delta\)S\({}^{\circ}\) and \(\Delta\)H\({}^{\circ}\)) and it was studied the adsorption kinetics and isotherm. At 25 \({}^{\circ}\)C was obtained the highest adsorption capacity of 16.4 and 7.4 mg/g with mass/volume ratio B 1:1 and modified corn (MC) respectively; it was observed an adverse effect of temperature increase on bioadsorbents' performance. The thermodynamic parameters showed that the adsorption process is exothermic, not spontaneous, and it was given by chemisorption. Adsorption kinetics showed that equilibrium was reached at 420 min and that the pseudo-second-order model adjusted the experimental data with R\({}^{2}\) > 0.98 and q\({}_{\text{e}}\) of 16.64 and 7.48 mg/g for B 1:1 as well as MC. The adsorption isotherm showed a good fit to [PERSON]'s model when using B 1:1, whereas using MC as adsorbents the data was adjusted by [PERSON]'s model. _Zea mays_ stems are an abundant agricultural residue and are a good source for the preparation of biochar type bioadsorbents as well as the extraction of cellulose, its use is recommended in the removal of sulfates in solution.  
biochar; adsorption kinetics; sulphate ions; corn; cellulose modification Article  
Efficient Sulfate Adsorption on Modified Adsorbents Prepared from _Zea mays_ Stems  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] of lignocellulosic origin have been traditionally implemented in adsorption processes. However, a few adsorbents derived from cornstalks have been implemented in the removal of anions [10; 11], and these adsorbents have been studied in terms of the kinetic and equilibrium study of adsorption, as well as thermodynamic analysis. The study of the adsorption rate also plays an important role in the implementation of adsorption technology for contaminant removal, since rapid adsorption is ideal, in order to reduce the cost of wastewater treatment and the consumption of time and energy entailed [12]. The adjustment to the kinetics models has contributed to the understanding of the process mechanism [13]. Isothermic study has helped to determine the affinity and interactions between the contaminants and adsorbent's active centers [14]. Numerical modelling based on thermodynamics provides an economical and accurate tool for studying the adsorption process, its costs and the effects of important parameters [15]. Therefore, this study focused on the evaluation of the effects of temperature on the adsorption capacity of sulfates in adsorbents prepared from cornstalks (_Zea mays_). Two bioadsorbents were prepared from biomass: a biochar modified with H\({}_{2}\)SO\({}_{4}\) at a mass/volume ratio of 1:1 (B 1:1) and cellulose modified with cetyl trimethyl ammonium chloride (CTAC). Their thermodynamic parameters (\(\Delta\)G\({}^{\circ}\), \(\Delta\)S\({}^{\circ}\) and \(\Delta\)H\({}^{\circ}\)) were determined, and the corresponding adsorption kinetics and isotherms were studied. This study also examined the kinetics and equilibrium of sulfate anion adsorption on the prepared bioadsorbents.