J. Betzabe González-Campos

Optimal planning for the sustainable utilization of municipal solid waste

The increasing generation of municipal solid waste (MSW) is a major problem particularly for large urban areas with insufficient landfill capacities and inefficient waste management systems. Several options associated to the supply chain for implementing a MSW management system are available, however to determine the optimal solution several technical, economic, environmental and social aspects must be considered. Therefore, this paper proposes a mathematical programming model for the optimal planning of the supply chain associated to the MSW management system to maximize the economic benefit while accounting for technical and environmental issues. The optimization model simultaneously selects the processing technologies and their location, the distribution of wastes from cities as well as the distribution of products to markets. The problem was formulated as a multi-objective mixed-integer linear programing problem to maximize the profit of the supply chain and the amount of recycled wastes, where the results are showed through Pareto curves that tradeoff economic and environmental aspects. The proposed approach is applied to a case study for the west-central part of Mexico to consider the integration of MSW from several cities to yield useful products. The results show that an integrated utilization of MSW can provide economic, environmental and social benefits.

Molecular dynamics analysis of PVA- AgnP composites by dielectric spectroscopy

The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS) in the 20-300°C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45°C until melting) associated to the α-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, the Tg of composites vary from 88*deg;C for pristine PVA to 125°C for PVA/AgnP (5wt%). Below 45°C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports.

New insights into the bactericidal activity of chitosan-Ag bionanocomposite: the role of the electrical conductivity.

The relationship between electrical conductivity, structure and antibacterial properties of chitosan-silver nanoparticles (CS/AgnP) biocomposites has been analyzed. To test the films antimicrobial activity, Gram-positive and Gram-negative bacteria were studied. The interactions between silver nanoparticles with chitosan suggest the formation of silver ions which plays a major role in nanocomposites bactericidal potency. In CS/AgnP biocomposites, the bactericide effectiveness increases by increasing AgnP concentrations up to 3 wt%, which is close to the electrical percolation threshold of ca. 3 wt%. As the AgnP concentration increases above this threshold, the bactericidal potency is greatly diminished. The elucidated correlation between electrical conductivity and antibacterial activity could be useful in the design of other nanocomposites that involve polymeric-based matrices.

Optimal reconfiguration of a sugar cane industry to yield an integrated biorefinery

The sugar cane production is one of the main economic activities of the agriculture sector in several places around the world. Nowadays, the sugarcane production zones face different technologic, economic, and social problems that impact negatively their profitability. The low price of sugar in the market demands the search of alternatives; being the bioethanol production from resides of the sugar cane industry an attractive option. This way, this paper presents a new approach for using the residues from the sugar cane industry to yield a sustainable biorefinery. In this approach, process integration techniques have been implemented to optimize the overall process. A case study from the State of Michoacán in Mexico is presented, where the proposed approach shows significant economic, environmental, and social benefits.

Optimal Multi-Objective Planning of Distributed Biorefinery Systems Involving Economic, Environmental and Social Aspects

Abstract This work presents a multi-objective optimization model based on a mathematical programming formulation for the optimal planning of distributed biomass conversion systems. The model considers the optimal selection of feedstocks, processing technologies and products while considering a time horizon. The multi-objective optimization problem simultaneously considers the profit maximization, the environmental impact minimization, as well as the maximization of the social impact benefit through the generation of jobs in rural areas. The economic objective function takes into account the availability of bioresources, processing limits and demand of products, as well as the cost of feedstocks, products and processing routes. The environmental impact is measured through the eco-indicator-99 based on the life cycle analysis methodology. The social impact is measured through the number of jobs generated. This formulation considers the variation of parameters over time. For instance, time-based profiles for raw-material availability and product demand are considered. Although the economic and environmental objectives may contradict each other with an influence on the social impact, by means of the proposed methodology is possible to obtain a set of Pareto curves that identify the set of optimal solutions for each objective. Each Pareto curve shows the compromise between the objectives and enables a better decision about the processing of biomass. The proposed methodology is applied to a case study for planning the production of a biorefinery system in Mexico, where several scenarios that compensate the economic, social and environmental objectives are identified.

A Mathematical Programming Approach for the Optimal Synthesis of Nanofibers through an Electrospinning Process

This paper presents a general mathematical programming formulation to determine the optimal operating conditions to synthesize nanofibers through an electrospinning process at minimum cost. Several relationships based on experimental data for different polymers to determine the nanofiber diameter and costs are proposed. Also, a general optimization approach is proposed to trade off the relationships between cost and nanofiber diameter. A case study including the specific relationships for three polymers and five operating conditions is presented. The proposed approach is general, and it can be applied to different cases.

Silver nanoparticles from AgNO3–affinin complex synthesized by an ecofriendly route: chitosan-based electrospun composite production

Abstract A novel nanofibrous chitosan-based composite containing affinin and silver nanoparticles is obtained by electrospinning. Silver nanoparticles are synthesized by sunlight photoreduction of the metal complex [Ag2–(affinin)](NO3)2 in polymeric solution, via a green one-pot methodology, wherein chitosan and affinin act as reducing, dispersing and stabilizing agent.

Chapter 19 – Supply Chains and Optimization for Biorefineries

Abstract This chapter presents an analysis of three main concepts involved in planning the supply chains for future biorefineries. First, the supply chain must include distributed systems that account for the economies of scale while simultaneously addressing the site selection for the installation of preprocessing hubs and central processing facilities. Second, the seasonal variation in the availability of the biomass resources must be considered in these supply chains. Finally, the optimal planning must take into account the multiobjective nature of the problem involving the optimization of the three aspects of a sustainable design: economic, environmental, and social issues. This chapter presents three mathematical programming models considering different key issues for the optimal planning of a biorefinery system and proposes procedures to solve these multiobjective problems. The proposed models were applied to several case studies for the optimal planning in Mexico where the importance of the key issues is highlighted.

A new type of anion receptor: pyrrolyl quinones

The synthesis of a novel 2-dipyrrolyl-2,5-dimethyl-p-benzoquinone is described, and its interactions with fluoride were characterized. An unprecedented interaction between fluoride anions and the quinone ring was observed.

Eco-friendly Production of Metallic Nanoparticles in Polymeric Solutions and Their Processing into Biocompatible Composites

Silver and gold nanoparticles were produced and embedded in poly(vinyl alcohol) (PVA) and chitosan (CTS) solutions by the photoreduction of metallic salt precursors triggered by direct sunlight irradiation, in which the polymers acted as reducing, dispersing and stabilizing agents. Sunlight photoreduction can be standardized using a constant UV index regardless of the season. This strategy was found to be an improvement over other common energy sources used to trigger the reduction of metal ions, including UV light irradiation and high-temperature reduction with mechanical stirring. The resulting PVA/metal nanoparticle and CTS/metal nanoparticle composite solutions were processed into thin films and nanofiber composites. In vitro testing of the cytotoxicity and biocompatibility demonstrates that the film composites are non-toxic and biocompatible with the HT-29 human colon cancer cell line. Promotion of HT-29 cell growth using our hybrid composites was observed, in contrast to other studies in which colloidal NPs were tested. Therefore, a sustainable approach for the onestep preparation of biocompatible polymer/metallic nanoparticle composites is reported.