Featured Application: The adsorbent materials under study could have a potential use for the decontamination of groundwater with high levels of arsenic and fluoride. It could be particularly suitable for application in water treatment for small communities.Abstract: The contamination of groundwater by arsenic and fluoride is a major problem worldwide, causing diseases in the population that uses these waters for their consumption. Therefore, the removal of these types of pollutants from groundwater is a very important issue. In this work, the removal of arsenate and fluoride from aqueous solutions by using aluminum-modified guava seeds (Al-GSs) was evaluated. Batch-type adsorption experiments were carried out with aqueous solutions of As(V) and F − and Al-GSs. The kinetic and equilibrium parameters of adsorption were determined, as well as the effects of adsorbent dose and pH. The adsorbent was characterized by scanning electron microscopy and infrared spectroscopy in order to determine its morphology and the functional groups present in the material. The results showed that hydroxyl and carboxyl are the main groups involved in the adsorption of As(V) and F − . The fluoride adsorption kinetics indicate that the equilibrium time was reached at 150 min and it can be described by the Lagergren model, while for As(V) the equilibrium time was lower (120 min) and the kinetic data were fitted well to the pseudo-second-order model. The Langmuir-Freundlich model can describe the adsorption equilibrium data in all cases. The fluoride adsorption capacity by Al-GS was 0.3445 mg/g, and for As(V) it was 4 mg/g. It can be established that the removal of arsenates and fluoride in Al-GSs is due to chemisorption on a heterogeneous surface.then consumption of these waters may lead to dental fluorosis. From 3 to 6 mg/L of fluoride, skeletal fluorosis may appear, and at higher fluoride levels (>10 mg/L) crippling skeletal fluorosis can be developed [3,4]; these types of fluorosis are irreversible, and no treatment can eliminate symptoms definitively. Keeping fluoride intake within safe levels is the only way to prevent these diseases [5,6]. People in several countries around the world are facing problems of high fluoride levels in drinking water; these problems are more severe and intense depending on different factors, like the geographical and economic status of the affected communities [7]. The World Health Organization (WHO) guidelines for drinking water quality have established that, for areas with a warm climate, fluoride concentration in water should remain below 1 mg/L, while this concentration could be raised up to 1.2 mg/ for areas with a cold climate [3]. In developing countries this problem is more acute, particularly in small urban communities and rural areas [5,8].On the other hand, arsenic content in drinking water is also a worldwide concern, and it represents a great threat to human health. Levels above 10 µg/L of arsenic, which is the maximum level recommended by the WHO, have been reported in drinking water from se...

This study aimed to evaluate and compare the relationship between chemical properties, energy efficiency, and emissions of wood and pellets from madroño Arbutus xalapensis Kunth, tázcate Juniperus deppeana Steud, and encino colorado Quercus sideroxyla Humb. & Bonpl. in two gasifiers (top-lit-up-draft (T-LUD) and electricity generation wood camp stove (EGWCS)) in order to determine the reduction of footprint carbon. In accordance with conventional methodologies, we determined the extracts and chemical components (lignin, cellulose, holocellulose), and the immediate analyses were carried out (volatile materials, fixed carbon, ash content and microanalysis of said ash), as well as the evaluation of emission factors (total suspended particulate matter (PM2.5), CO, CO2, CH4, black carbon (BC), elemental carbon (EC), and organic carbon (OC)). The results were statistically analyzed to compare each variable among species and gasifiers. The raw material analyzed showed how the pH ranged from 5.01 to 5.57, and the ash content ranged between 0.39 and 0.53%. The content values of Cu, Zn, Fe, Mg, and Ca ranged from 0.08 to 0.22, 0.18 to 0.19, 0.38 to 0.84, 1.75 to 1.90, and 3.62 to 3.74 mg kg−1, respectively. The extractive ranges from cyclohexane were 2.48–4.79%, acetone 2.42–4.08%, methanol 3.17–7.99%, and hot water 2.12–4.83%. The range of lignin was 18.08–28.60%. The cellulose content ranged from 43.30 to 53.90%, and holocellulose from 53.50 to 64.02%. The volatile material range was 81.2–87.42%, while fixed carbon was 11.30–17.48%; the higher heating value (HHV) of raw material and pellets presented the ranges 17.68–20.21 and 19.72–21.81 MJ kg−1, respectively. Thermal efficiency showed statistically significant differences (p < 0.05) between pellets and gasifiers, with an average of 31% Tier 3 in ISO (International Organization for Standardization) for the T-LUD and 14% (ISO Tier 1) for EGWCS, with Arbutus xalapensis being the species with the highest energy yield. The use of improved combustion devices, as well as that of selected raw material species, can reduce the impact of global warming by up to 33% on a cooking task compared to the three-stone burner.

In this paper, the removal of Pb(II) ions from aqueous solutions using cellulose nanofibers (NFC) and crystalline nanocellulose (CNC) was studied. These adsorbents were obtained from water hyacinth (Eichhornia crassipes) by the Kraft process. Characterization was carried out to NFC and CNC by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), showing excellent structural properties and high availability of surface functional groups. The influence of different parameters on the adsorption process was evaluated through batch-type adsorption experiments. The results showed effective Lead removal reaching adsorption equilibrium at 180 min. Isotherms results showed maximum adsorption capacities (Qmax) of 80.02, 84.64, and 87.10 mg/g for NFC at 25, 30 and 45 °C, respectively. Results of Pb(II) adsorption isotherms by CNC showed a Qmax of 17.90, 28.20, and 30.36 mg/g at 25, 30 and 45 °C, respectively. Isotherm data were best described by the Langmuir-Freundlich model for NFC, and the Freundlich model best-described CNC isotherm. Lead adsorption mechanisms were different for both biosorbents. The thermodynamic parameters of the process were calculated. Endothermic reactions were observed for both materials. NFC and CNC materials have great potential as biosorbents for the removal of lead ions from water.

The global need to transition to renewable and decentralized systems entails agricultural systems as producers of residual biomass. Avocado trees (Persea americana Mill.) are one of the main woody crops cultivated in Mexico, with over 150,000 hectares grown in the country. The aim of the present study is to evaluate the use of avocado pruning residues as an energy input, focusing on the revalorization of biomass and the generation of economic benefits for small producers in the region. For that purpose, we developed allometric equations to calculate biomass availability from pruning residues, evaluated their thermochemical properties, and proposed technological alternatives for their energy use. Two allometric equations for pruning residues as a function of tree height and crown diameter were obtained: one for light and minor maintenance pruning (R2 = 0.63) and one for rejuvenation pruning (R2 = 0.86). From these equations, we estimate the mean amount of biomass generated from light and rejuvenation pruning to be 42.7 and 25.1 kg per tree and year, respectively, which amounts to 1324 and 780 kg ha−1 DM (dry matter), with an energy potential of 26.2 and 15.4 GJ ha−1. The thermochemical analysis shows that a higher proportion of leaves generates a higher ash content, which reduces the quality of the residues as a fuel. Avocado pruning residues have high potential for energy use and could be implemented in the industrial and residential sectors, generating a complementary source of income for producers.

Eichhornia crassipes (water hyacinth) was pulped by means of a kraft pulping process with reagent loads of 10 and 20% on a dry matter basis to determine yield, rejects, kappa number, and ash. Fiber classification, brightness, opacity, and viscosity were measured in the brown pulp. Bleaching was performed by means of an O1O2D1(PO)D2HD3 sequence. Yield, kappa number, pH, ash, brightness, opacity, and viscosity were evaluated in the bleached pulp. Finally, a microanalysis of inorganic elements was carried out in both the bleached and unbleached pulp ash. The highest kraft pulp yield was 26.4%, with a 10% reagent load at 120 °C and 30 minutes cooking. It was determined that E. crassipes cellulosic pulp contains large amounts of fines. Results of the bleaching sequence indicate low brightness (58.0 %) and low viscosity (6.43 cP). The most abundant inorganic elements in the ash of both bleached and unbleached pulp were Ca, Mg, P, and Si. These results suggest that E. crassipes biomass might complement cellulosic fibers in pulping processes of low yield, such as the wood fibers used to produce handmade paper.