![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20081108011849im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Final Report: Synthesis of a Polymeric Hybrid Ion Exchanger with Recovered Iron(III) Towards the Removal of Arsenic
EPA Grant Number: SU831820Title: Synthesis of a Polymeric Hybrid Ion Exchanger with Recovered Iron(III) Towards the Removal of Arsenic
Investigators: SenGupta, Arup K. , Blaney, Lee M. , Greenleaf, John
Institution: Lehigh University
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: September 1, 2004 through May 30, 2005
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity, and the Planet (2004)
Research Category: Drinking Water
Description:
Objective:An estimated 10,000 tons of drinking water sludges are generated globally each day. These sludges contain the sediment, suspended, and flocculated particles removed during the coagulation process. Many water treatment plants around the world use ferric salts, FeCl3 or Fe2(S04)3, as coagulants because of their excellent ability to remove organics and low cost. Of the solids present in the sludge, approximately 25-50% are composed of ferric hydroxides formed due to the use of ferric salts as coagulant. According to current EPA regulations, this sludge must be disposed of into landfills. Therefore, each year millions of tons of ferric hydroxide laden sludges are transported and disposed of into landfills; this immense operation costs the water treatment industry millions of dollars each year.
Meanwhile, half way around the world, an environmental health disaster is occurring as tens of millions of people in West Bengal, India and Bangladesh have been drinking arsenic contaminated water for the past two decades. Thousands of people have already died and some estimates state that over one hundred million more are at risk of developing arsenicosis, or arsenic-poisoning. The symptoms of arsenicosis range from skin lesions and gangrene to circulatory system problems; however, the most terrible effect is the associated high incidence of skin, lung, bladder, and kidney cancer.
The two environmental crises described above are unrelated and are occurring in different worlds. Nevertheless, this project proposes a method for solving the coagulant consumption problems of the developed world towards the generation of raw materials to help alleviate the environmental disaster happening in the undeveloped world.
In order to lessen the massive waste generation of ferric hydroxide loaded sludge, the Donnan Membrane Process will be used to efficiently recover ferric ions from sludge, or water treatment residuals. These ferric ions will then be used to impregnate an ion exchange resin creating an arsenic-selective, hybrid ion exchange sorbent, which has been shown to effectively remove arsenic from water supplies.
Summary/Accomplishments (Outputs/Outcomes):The Donnan Membrane Process part of the project performed as expected: 75% of the Fe(III) present in water treatment residuals was recovered in a 24 hour period. This accomplishment is notable as the process allows for high coagulant recovery over short periods of time with minimal operating costs. The capital investment is recovered through the diminished need for raw coagulant purchase and decreased disposal costs.
The utilization of recovered ferric ions in the synthesis of the hybrid ion exchange sorbent turned out to be inefficient. The low pH of the recovered Fe(III) solution caused selectivity reversal in the exchange resin; therefore, significant loading of hydrated ferric oxide particles into the resin’s macro-pores did not occur. This problem was heightened by the relatively dilute recovered ferric solution which did not allow for high iron uptake.
Experiments using more dilute acids as sweep solutions allowed for an ideal final sweep pH; however, the Fe(III) concentration was then too low for an economically efficient loading process to be utilized. Other tests were performed using the recovered iron solution in combination with a virgin iron solution; however, due to the low concentration (as compared to the 4% used in previous studies) the solution volume to resin mass ratio increased significantly. An increase in this ratio creates an economically inefficient process as the benefits of using recovered iron solution become diluted by the larger reactor volumes needed and the need for an outside iron source. Another remedy towards this problem would be the addition of a strong base to the recovered solution in order to raise the PH; however, that operation would make the process too complex and undesirable compared to the use of stock iron solution.
All of these options listed above towards the development of a hybrid ion exchanger using recovered iron are possible; however, the inputs or efficiencies of those processes do not meet the requirements of this project as they are significantly less attractive than processes utilizing virgin iron solution.
Conclusions:The complications which arose in development of the hybrid ion exchanger part of the project create a situation where introduction of this project into industry is unrealistic. In both theory and practice the process can still be carried out with the necessary adjustments being performed; however, it would not be in the economic interest of industry to proceed along that avenue.
Even though the overall project did not perform as expected, the Donnan Membrane Process part of the project offers much potential for the movement towards sustainability. This potential lies in the economic sensibility of the coagulant recovery process, which concurrently reduces human impact on the environment.
The project was planned to be a combination of two previous projects; however, due to the complications which arose during experimentation, the project’s new goal is toward the implementation of the Donnan Membrane Process into industry. The benefits offered to the planet and economic prosperity with the newly designated project goal are vast. The continued availability of clean drinking water and lower municipal taxes are some of the advantages to be enjoyed by the greater public.
Regardless of the failure of the original project proposal in respect to the detailed benefits to people, prosperity, and the planet, the results of Phase I do have merit in the sustainability movement. This merit is present through the capabilities offered through the Donnan Membrane Process. These capabilities fit the requirements of the P3 Award nicely as the benefits to people, the planet, and prosperity are easily quantifiable and advantageous. For this reason, the research objectives of Phase II will center on further development of the Donnan Membrane Process.
The ability to succeed in laboratory scale projects is extremely important to the spread of the sustainability movement and the innovation of new ideas; however, without real-world, working models, implementation into industry is often a slow process. For this reason, it is felt that design of a full scale Donnan Membrane Process unit for use in a typical water treatment plant along with construction of a pilot reactor would be highly beneficial to the furthering of this extremely advantageous process in the water treatment industry.
By utilizing the governing equations of the Donnan Membrane Process and the design of existing membrane processes which maximize contact area, a numerically-based computer model detailing an efficient prototype design will be created. This model will then be realized in the form of a pilot-scale prototype that will provide a working example of the process.
The data taken from the pilot reactor will be similar to that discussed in Phase I: available exchange area, feed to sweep volumes, sweep characteristics, recovery percent, and capital/operating costs. The values of these parameters will be taken from the design characteristics, materials costs, and analysis of the feed and sweep solutions. Analysis of these two solutions will be completed using a Perkin Elmer Atomic Absorption Spectrometer (Model Analyst 100) and a Dionex Ion Chromatograph (Model DX- 120 IC). This data will then be scaled up to characterize the actual workings of the Donnan Membrane Process on a plant scale so as to provide a persuasive argument to the industry towards the implementation of a Donnan Membrane Process coagulant recovery unit.
The Civil and Environmental Engineering Department at Lehigh University has worked closely with the Allentown Water Treatment Plant in Allentown, PA and the Baxter Water Treatment Plant in Philadelphia, PA for many years on issues relating to water treatment and coagulant recovery. After the data has been gathered and organized, detailed process reports will be sent to these respective plants. The directors of the plants will be invited for a demonstration on the operational simplicity and economic potential provided by such a reactor. Hopefully, these officials will like what they see and consider adopting similar processes and reactors at their respective plants. Published results and advertisement of the abilities of a full scale Donnan Membrane Process reactor towards coagulant recovery will operate as further forms of persuasion towards the implementation of sustainable practices at water treatment plants.
Supplemental Keywords:Phase I only: Adsorption, Heavy Metals, Remediation, Cleanup, Groundwater, Metals, Health Effects, International Cooperation, Pollutants/Toxics, Treatment/Control, RFA, Scientific Discipline, Arsenic, Water Pollutants, Risk Management, Arsenic Removal, Polymeric Hybrid Ion Exchanger
Phase II: Waste Reduction, Coagulant Recovery, Sustainable Development, Ion Exchange, Cation Exchange Membranes, Donnan Membrane Process, Water, Chemical Engineering, Chemistry, Drinking Water, Environmental Chemistry, New/Innovative Technologies, Technology, Clean Technologies, Drinking Water System, Drinking Water Distribution System, Drinking Water Treatment, Drinking Water Treatment Facilities, Green Chemistry, Green Engineering, Sustainable Industry/Business, Chemical Reuse, Donnan Membrane Process Reactor, Pilot-scale Reactors
, POLLUTANTS/TOXICS, Water, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, Scientific Discipline, RFA, Arsenic, Drinking Water, Chemical Engineering, Technology, Chemistry, Water Pollutants, Environmental Chemistry, New/Innovative technologies, Environmental Monitoring, drinking water system, drinking water contaminants, clean technologies, arsenic removal, green chemistry, drinking water distribution system, detoxification, Other - risk management, polymeric ligand exchangers, drinking water treatment, ion exchange, green engineering, drinking water treatment facilitiesProgress and Final Reports:
Original Abstract