wastewater

One of the environmental challenges of various industries is the removal of heavy metals from aquatic environments. Nowadays, the use of adsorption method is considered as an efficient method to overcome this challenge. Although, the physical and chemical characteristics of the sorbent are of particular importance. In this research, the efficiency of an activated carbon sample modified with rhamnolipid biosurfactants was evaluated in order to remove copper ions from the aqueous environment.

For this purpose, the effect of some operational parameters including the ratio of adsorbent to metal (50 to 200), initial solution pH (4 to 10) and stirring speed (100 to 300 rpm) on copper removal efficiency in the form of a central composite experimental design was investigated. The results of experimental studies were evaluated using statistical modeling and analysis of variance.

The statistical analysis of the results revealed that the effect of all parameters on the adsorption efficiency was significant, so That the efficiency increased with the increase of the ratio of adsorbent to metal and pH, and with the decrease of the stirring speed. As a result of optimizing the process, the removal efficiency of more than 99% was achieved under the ratio of adsorbent to metal of 200, pH of 7 and stirring speed of 100 rpm. Additional studies under optimal conditions showed that the process follows pseudo-second-order kinetics and the Freundlich isothermal adsorption model. Moreover, thermodynamics and multistep adsorption studies showed that the adsorption of copper on the modified adsorbent is a two-step process including a high-rate primary chemical adsorption followed by a slow physical secondary adsorption, likely precipitation. The evaluation of absorption selectivity also indicated substantially adverse effect of other metals on the absorption rate of copper ions.

The results of this research showed that activated carbon improved with rhamnolipid biosurfactants can be used as a promising and efficient sorbent for the treatment of wastewater contaminated with heavy metals.

Until now, various chemical treatments (oxidation and electrochemical destruction), biological treatments (microbial cultures and anaerobic bioremediation systems) and physical treatments (such as adsorption and ion exchange) have been proposed to remove dyes as one of the most important water pollutants. In this study, hydrodynamic cavitation (bubble formation in a liquid) was considered as a new method for dye removal. The important advantages of this method are no need to use chemicals, low energy consumption and the ability to combine with other advanced oxidation processes. A literature review on dye removal focusing on combination with other advanced oxidation processes indicated that orifice plates and venturi tubes are often used and less than 2 h (in optimum operating conditions) more than 80% of dye was removed. Also, factors such as device geometry, inlet pressure, operating temperature, pH and liquid properties (like vapor pressure, viscosity and surface tension) are effective parameters in this process. The results of previous works imply excellent efficiency of this method in combination with other processes and methods such as Fenton, photocatalytic, ozonation, aeration and presence of various metal and non-metallic ions in the reaction medium. Also, flexibility in designing and combining with advanced oxidation processes, depend on the purpose, are another major and important advantages for replacing this method with conventional methods in the near future.

The presence of heavy metal ions in polluted wastewater represents a serious threat to human health, making proper disposal extremely important. The utilization of nanofiltration (NF) membranes has emerged as one of the most effective methods of heavy metal ion removal from wastewater due to their efficient operation, adaptable design, and affordability. NF membranes created from advanced materials are becoming increasingly popular due to their ability to depollute wastewater in a variety of circumstances. Tailoring the NF membrane’s properties to efficiently remove heavy metal ions from wastewater, interfacial polymerization, and grafting techniques, along with the addition of nano-fillers, have proven to be the most effective modification methods. This paper presents a review of the modification processes and NF membrane performances for the removal of heavy metals from wastewater, as well as the application of these membranes for heavy metal ion wastewater treatment. Very high treatment efficiencies, such as 99.90%, have been achieved using membranes composed of polyvinyl amine (PVAM) and glutaraldehyde (GA) for Cr3+ removal from wastewater. However, nanofiltration membranes have certain drawbacks, such as fouling of the NF However, nanofiltration membranes have certain drawbacks, such as fouling of the NF membrane. Repeated cleaning of the membrane influences its lifetime. membrane. Repeated cleaning of the membrane influences its lifetime.

Heavy metals are extremely harmful environmental pollutants due to their toxicity, non-biodegradability and environmental accumulation that can affect people and the environment. Microbial fuel cells are a type of bioelectrochemical approach in which bacterial species remove organic pollutants and metal ions from synthetic and industrial wastewater and simultaneously generate electricity. Currently, the real applications of these devices in the world are limited due to the low level of production density. According to the investigations carried out in this article in recent years, microbial fuel cells have been used as one of the ways to remove heavy metals from industrial effluents, and 10 to 100% removal rates were achieved for metals such as gold, chromium, copper, lead, cadmium, mercury, zinc, arsenic and nickel. Also, the parameters affecting the amount of removal were evaluated in these studies, and the optimal conditions are in most cases in the range of neutral pH and in some cases in pH=2, at a temperature of 22 to 35 0C and an external resistance of 200 to 1000 ohms.

In recent years, the textile industry has produced more than 50 % of the colored wastewater in the world. Clean water is essential in the lives of humans, aquatic organisms, and agricultural products. Due to their toxicity, dyestuff in water causes adverse quality, endangers their health, and causes environmental changes. There are different methods for wastewater treatment, which, based on the research, shows that today's surface absorption method is mainly used for wastewater treatment due to its cheapness, simplicity, and cost-effectiveness. In this article, the removal of dyestuff from wastewater was investigated using different nanocomposites, and the effect of adsorption with nanocomposites was investigated based on factors affecting adsorption, including contact time, initial concentration, the effect of temperature, and pH of the solution. Adsorbents significantly impact removing dyestuff and can perform wastewater treatment with good quality. This research used activated carbon nanocomposites, carbon nanotubes, silver nanoparticles, zinc ferrite, ZnO, TiO2</sub>, Fe3</sub>O4</sub> and zero-valent iron nanoparticles for wastewater decolorization. In this article, the results show that different nanocomposite adsorbents are promising. They are a promising future for the treatment of colored wastewater.  

Dyes have many uses due to their variety and complex structure.In recent years, wastewater from the production or consumption of dyes in various industries have increased and become a serious threat to the environment and human health.The effect of cold plasma as a new and advanced technology for the treatment of dye from wastewater is presented in this review paper. This method can be used for various applications such as treatment and pre-treatment of effluents, removal of pigments, and hazardous chemicals from effluents.In this wastewater treatment system, different cases such as characteristics of effluent, target materials, type of suitable plasma discharge, reactor type, toxicity experiments, biodegradability tests of plasma generated intermediates, environmental compatibility assessment of combined technologies, and economic estimation were considered. According to the studies, the results indicated the positive effects of cold plasma for decolorization of wastewater and also increased efficiency of modern wastewater treatment systems.  

Industrial wastewater have metal ions and colour compounds which can be harmful for human and animals and causing serious diseases such as cancer, damaging of nervous system, organ damage and even death. So, the removal of these materiales from waters and wastewaters is very important. Different methods have been used to remove heavy metals from wastewater such as precipitation, ion exchange, electrodialysis and reverse osmosis, that these methods are inefficient and expensive. Among these methods, adsorption is an efficient method for water treatment and wastewater decolorization, because of its low cost, easy operation, environmental friendly, high efficiency and low energy. The adsorbents used are mostly natural modified materials, agricultural waste and many micro-organism species. In this article, some of the natural adsorbents and biosorbents including bagasse, onion skin, algae, etc. have been introduced