Recently many researchers have proved the capability of agricultural solid wastes as adsorbents to remove many types of pollutants including dyes. This review represents the use of agricultural solid wastes to remove two classes of dye, cationic and anionic dyes and makes a simple comparison among cationic and anionic dye adsorption by the same adsorbent, thus possibly opening the door for a better understanding of the dye-classified adsorption process. Both these classes of dyes are toxic and cause severe problems to aquatic environment. Some agricultural solid wastes can remove both dye classes, although they need activation. The dye adsorption capacities of agricultural waste adsorbents vary, depending on the pH of solution, initial dye concentration, adsorbent dosage and process temperature. The pH of solution is directly related to the dye-classified adsorption, where it affects the surface charge of the adsorbent and the degree of ionization of the adsorbate.

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Many cities in developing Asian countries face serious problems in managing solid wastes. The annual waste generation increases in proportion to the rises in population and urbanization. Asian countries with greater rural populations produce more organic waste, such as kitchen wastes, and fewer recyclable items, such as paper, metals, and plastics. Reliable data on solid waste compositions are difficult to obtain, and even if available, they are often not updated. We report the most recent waste composition data in some developing Asian countries. We suggest that a better classification system for landfills is needed to address inconsistencies in data for sanitary landfill sites versus waste dumps. We also discuss the information on waste disposal trends and problems associated with general solid waste management in developing Asian countries.

Palm oil mill effluent (POME), a pollutant produced by the palm oil industry, was treated by the Vetiver system technology (VST). This technology was applied for the first time to treat POME in order to decrease biochemical oxygen demand (BOD) and chemical oxygen demand (COD). In this study, two different concentrations of POME (low and high) were treated with Vetiver plants for 2 weeks. The results showed that Vetiver was able to reduce the BOD up to 90% in low concentration POME and 60% in high concentration POME, while control sets (without plant) only was able to reduce 15% of BOD. The COD reduction was 94% in low concentration POME and 39% in high concentration POME, while control just shows reduction of 12%. Morphologically, maximum root and shoot lengths were 70 cm, the number of tillers and leaves was 344 and 86, and biomass production was 4.1 kg m−2. These results showed that VST was effective in reducing BOD and COD in POME. The treatment in low concentration was superior to the high concentration. Furthermore, biomass of plant can be considered as a promising raw material for biofuel production while high amount of biomass was generated in low concentration of POME.

In this review, reports, patents and recently published papers and documents on polyurethane recycling, especially chemical recycling methods, are investigated in order to find an adequate method for waste reduction, protecting the environment and preventing waste land filling. The recycling of polyurethane has always posed unique challenges due to its wide variety of applications, from the industry to bio-based materials, namely, artificial organs. Mechanical regrinding is the oldest method in polyurethane waste recycling and the use of the regrind wastes as filler in the new formulations. Chemical recycling of polyurethanes by hydrolysis, aminolysis and glycolysis is for the most part considered economically uncompetitive compared to formulating with virgin raw materials. Also some thermochemical processes are utilized for PU recycling. Recycling has opened an effective and economic route for polyurethane waste treatment. Nonetheless, more research efforts are required in order to scale up the recycling methods.