Boron removal from seawater by Hybrid Solar Photovoltaic Electrocoagulation (SPEC) Process

Abstract

Excess boron ion in drinking and irrigation water is a serious environment and health problems because it can be toxic to many crops and lead to various human and animals diseases with long-term consumption. Desalinated seawater from reverses osmosis (RO) plants often contains high boron content and need an expensive second pass RO membrane treatment, which calls for sustainable, cheaper and reliable alternatives. The current research studies the feasibility of the boron removal from synthesized water and real seawater using hybrid solar photovoltaic electrocoagulation (SPEC) process. Batch EC experiments were carried out on a laboratory scale using aluminum electrodes powered by solar photovoltaic energy to investigate several operational parameters on the boron removal efficiency such as current density, initial pH, initial boron concentration, supporting electrolyte type and concentration, electrodes material, gap between electrodes, stirring speed and anodes surface area to reactor volume ratio. Optimum removal efficiency (90.6%) corresponding to a final boron concentration of (0.47 mg/L) was achieved with parameter values of current density (4.17 mA/cm2), initial pH (7) and NaCl concentration (1.0g/L) within 120 min operating time. The corrosion of electrodes was characterized using FESEM. By-products obtained from the electrocoagulation cell were analyzed and explained using FTIR and XRD. Furthermore, a comparison between SPEC and conventional electrocoagulation was carried out. Results showed higher energy consumption using conventional power source compered to solar power source in order to achieve same boron removal efficiency. Use of batteries followed by DC-DC charge controller with photovoltaic panels provided more regular and efficient performance for the SPEC system. The obtained optimum conditions were applied to treat real seawater. The results showed that boron residual concentration in seawater decreases with an increasing electrolysis time and electrodes consumption. Comparative cost estimation with different operating parameters for synthetic and real seawater was adopted and presented as well. This study indicates that, SPEC is a promising alternative for the efficient removal of boron from seawater, which could be used as a pretreatment unit in a desalination plants.