Aluminum sulfate is one of the most used chemical coagulants in the world, but research has shown that high concentrations of aluminum in the body are associated with neuropathological conditions. Because of this, different alternatives have been evaluated such as natural coagulants, which are considered safe for human health and contain fewer contaminants than chemicals due to their biodegradation properties. The main objective of this study was to evaluate the efficiency of mixing nopal mucilage and cassava starch for turbidity removal in water purification. In this paper, test jars and the treatment equipment (TA-scale FQ-005/PE manufactured by Generatoris SA de CV of Mexico) was applied in order to measure turbidity and pH parameters before and after the process of coagulation–flocculation, which was applied to water from the Magdalena River in Colombia. Samples from two sampling periods were assessed. One was evaluated during the rainy season and the other was evaluated without precipitation (drought) with initial turbidities of 316 NTU and 80 NTU, respectively. It was found that aluminum sulfate as a coagulant reference obtained better turbidity removal results (up to 99%) as compared to nopal (up to 60.4%), and nopal–starch combination of cassava (up to 67%), indicating that this mixture increases the effectiveness of natural coagulants used individually. Our results indicate that this should be considered as an alternative in the water purification process.

The main objective of this study was to evaluate the adsorption efficiency for removing nitrate and phosphate in an aqueous solution using adsorbents derived from rice husks and corn stalks. Five adsorbents were used: untreated rice husk (RH), raw corn stalk (CS), rice husk biochar (RHB), corn stalk biochar (CSB), and a rice husk biochar chemically modified with magnesium (RHB-Mg). The influence of operational variables (temperature, pH, adsorbent dose, and initial concentration) on individual and competitive adsorption of nitrate and phosphate was studied together with adsorption equilibrium and kinetics. The results showed that the best adsorbent was RHB-Mg, with maximum adsorption capacities of 111.10 mg/g for phosphate and 35.11 mg/g for nitrate, determined from Langmuir isotherm. Competitive adsorption of nitrate and phosphate was favorable using RHB-Mg, demonstrating that RHB-Mg could be used to remove these nutrients from wastewater.

This article analyzed 26 countries’ long-term relationship between the nominal exchange rate, international palm oil prices, and exports competitiveness from 2007 to 2015. Unit root tests, Kao-Padroni joint tests, a fully modifiable ordinary least squares, and a dynamic ordinary least squares model were used. It was found that an increase in the exchange rate favored palm oil exports’ competitiveness as well as a decrease in its price. This study determines the competitiveness of crude and refined palm oil exports through non-conventional statistical analysis.

Water purification is indispensable to guarantee safe human consumption and to prevent diseases caused by the ingestion of contaminated water. This requires a series of water treatment processes which require investment. However, the economic limitations of rural communities hinder their ability to implement such water-treatment systems, as is the case in Ciénaga Grande of Santa Marta ("Large Swamp", in English) in Colombia. Low-cost systems can be used instead as simple and safe alternatives. Therefore, the objective of this work was to evaluate non-conventional, low-cost water processes to purify the water from the collection point of two stilt house villages in Ciénaga Grande of Santa Marta. These include: 1) Using two natural coagulants, Moringa Oleifera and Cassia Fistula; 2) filtration through a biosand filter and a carbon activated filter; and 3) disinfection through UV-C Radiation and through solar disinfection. The results showed a turbidity values reduction between 52% and 96% using the two natural coagulants; both turbidity and total coliforms achieved reductions of 98.4% and 76.9%, respectively in the filtration process; and removal of total coliforms up to 98.8% in the disinfection process. Despite the high rates of reduction in the different parameters, the water does not comply with the recommended limits for safe drinking water.

This review critically analyzed the use of biosorbents derived from rice husks and corn residues for nutrient removal from aqueous solutions. Additionally, this review highlighted the use of such biosorbents in wastewater treatment. Furthermore, novel approaches for sustainable nutrient removal from aqueous solutions were identified. A comprehensive understanding of the implementation of biosorption processes using agro-industrial residues based on corn and rice crops is critical for the sustainable management of residues and water bodies in the world to protect and conserve natural resources. Specifically, the review focuses on the exploration, preparation and application of innovative biosorbents to remove various forms of nutrients such as total nitrogen, total phosphorus, nitrates, ammonium and phosphates from aqueous solution, analyzing the sustainability of treatments applied to biomass, such as thermal transformation or chemical modification to reduce environmental impacts. It was found that 95 to 99% of nitrogen and phosphorus can be removed with biosorbents made from rice husks and corn residues, analyzing approximately 50 scientific articles related to these plant materials. Research opportunities were identified, such as the recovery of removed nutrients for soil improvement, life cycle analysis to assess the concept of zero waste, among other aspects. Finally, a scheme is proposed for the selection and application of sustainable biosorbents for the removal of nutrients from aqueous solutions.